Executive Summary
Week 5 of 2026 presents four epidemiologically significant developments requiring immediate public health attention. First, Bulgaria’s acute viral hepatitis notifications reached 185 cumulative cases through Week 5, representing a 198% increase over the 62 cases reported during the same period in 2025, with 43 cases in Week 5 alone—a signal demanding urgent virological investigation to identify causative agents and transmission pathways. Second, campylobacteriosis in Bulgaria showed a 193% year-over-year increase (44 cases versus 15 cases), suggesting potential food safety breaches or environmental contamination requiring immediate investigation. Third, the European Medicines Agency approved Kayshild (semaglutide) as the first GLP-1 receptor agonist for metabolic dysfunction-associated steatohepatitis with liver fibrosis, addressing a condition with no previously authorised pharmacological treatment and significant implications for non-alcoholic fatty liver disease management across Europe. Fourth, the Netherlands reported avian influenza A(H5N1) antibodies in a dairy cow—the first such detection in the EU/EEA and only the second country globally after the United States to identify cattle exposure to highly pathogenic avian influenza, raising concerns about potential mammalian adaptation and zoonotic transmission pathways beyond poultry.
Non-Communicable Disease and Healthcare System Developments
The European Medicines Agency’s Committee for Medicinal Products for Human Use convened from 26 to 29 January 2026 and recommended six new medicines for marketing authorisation, alongside nine extensions of therapeutic indications for existing medicines. These regulatory actions address significant gaps in treatment options across multiple therapeutic areas and carry immediate clinical implications for EU/EEA healthcare systems.
Kayshild (semaglutide) received conditional marketing authorisation for the treatment of non-cirrhotic metabolic dysfunction-associated steatohepatitis with liver fibrosis, representing the first GLP-1 receptor agonist approved for this indication. Metabolic dysfunction-associated steatohepatitis—the progressive inflammatory variant of metabolic dysfunction-associated liver disease—affects substantial proportions of populations with obesity and type 2 diabetes, leading to hepatic fibrosis, cirrhosis, and hepatocellular carcinoma in the absence of effective pharmacological intervention. Although several GLP-1 receptor agonists have received approval for type 2 diabetes mellitus and obesity management across the EU/EEA, this represents the first authorisation specifically targeting the hepatic manifestations of metabolic syndrome. The conditional approval mechanism requires post-authorisation studies to confirm clinical benefit, reflecting the urgent unmet medical need in this population. Given the rising prevalence of metabolic syndrome across Europe and the established relationship between obesity, insulin resistance, and progressive liver disease, this approval has significant implications for hepatology and endocrinology practice. Clinicians managing patients with metabolic dysfunction-associated liver disease now have an evidence-based pharmacological option beyond lifestyle modification, potentially altering disease trajectories and reducing progression to cirrhosis and hepatocellular carcinoma.
Kygevvi (doxecitine/doxribtimine) received a positive opinion under exceptional circumstances for thymidine kinase 2 deficiency, an ultra-rare autosomal recessive mitochondrial disorder affecting fewer than one in one million individuals. Thymidine kinase 2 catalyses the rate-limiting step in mitochondrial DNA synthesis, and loss-of-function mutations lead to mitochondrial DNA depletion particularly affecting tissues with high energy demands. Clinical manifestations include progressive external ophthalmoplegia, proximal myopathy, exercise intolerance, respiratory insufficiency, and substantially shortened life expectancy, with symptom onset typically in childhood or early adulthood. Prior to this approval, no disease-modifying treatments existed; clinical management consisted entirely of supportive measures including nutritional support via gastrostomy, respiratory support via non-invasive or invasive ventilation, and physiotherapy to maintain functional capacity. The approval under exceptional circumstances reflects the impossibility of obtaining comprehensive efficacy data in such an ultra-rare condition, where affected individuals number in the hundreds globally. This medicine was supported through the European Medicines Agency’s PRIority MEdicines scheme, which provides enhanced scientific and regulatory guidance for therapies addressing unmet medical needs. The availability of disease-modifying treatment for this devastating condition represents a transformative development for affected families, though post-authorisation monitoring will be essential to characterise real-world effectiveness and safety in this heterogeneous patient population.
Rezurock (belumosudil) received conditional marketing authorisation following re-examination for chronic graft-versus-host disease, a major complication of allogeneic haematopoietic stem cell transplantation in which donor immune cells mount an inflammatory response against recipient tissues. Chronic graft-versus-host disease affects multiple organ systems including skin, oral mucosa, gastrointestinal tract, liver, lungs, and joints, causing substantial morbidity and mortality in transplant recipients. The committee concluded that Rezurock should be utilised when other treatment options provide limited clinical benefit, are unsuitable for the patient, or have been exhausted. This positioning reflects the challenging therapeutic landscape in refractory chronic graft-versus-host disease, where treatment options become progressively limited after failure of first-line corticosteroid therapy and second-line immunosuppressive agents. The conditional approval reflects the need for additional confirmatory evidence while providing immediate access to a therapy addressing a high unmet need in a severely affected population. For haematology and transplantation services across the EU/EEA, this approval provides an additional option for patients experiencing treatment-refractory chronic graft-versus-host disease, though careful patient selection according to prior treatment exposure and organ involvement will be essential.
Fylrevy (estetrol) received marketing authorisation for hormone replacement therapy addressing oestrogen deficiency symptoms in postmenopausal women. During the menopausal transition, ovarian follicular depletion leads to declining oestrogen production, manifesting as vasomotor symptoms including hot flushes, night sweats, and associated sleep disturbance, as well as genitourinary symptoms, mood changes, and increased cardiovascular and skeletal risks. Estetrol is a naturally occurring oestrogen produced by the foetal liver during pregnancy, with a unique receptor binding profile and pharmacokinetic properties distinguishing it from endogenous oestrogens and synthetic oestrogen derivatives currently used in hormone replacement therapy. This approval expands the therapeutic options available for managing menopausal symptoms, adding to the existing portfolio of oestrogen-only and combined oestrogen-progestogen formulations. The clinical significance depends on estetrol’s comparative safety profile relative to existing hormone replacement therapies, particularly regarding thromboembolic and cardiovascular risks that have shaped prescribing patterns since publication of the Women’s Health Initiative results in 2002.
Ilumira (lutetium-177Lu chloride) received a positive opinion as a radiopharmaceutical precursor for radiolabelling of carrier molecules specifically developed and authorised for lutetium-177 conjugation. Lutetium-177 is a beta-emitting radionuclide with favourable physical characteristics for targeted radionuclide therapy, including a 6.7-day half-life, maximum beta energy of 498 keV with a tissue penetration range of approximately 2 millimetres, and accompanying gamma emissions enabling imaging and dosimetry. When conjugated to tumour-targeting molecules such as peptides binding to somatostatin receptors or prostate-specific membrane antigen, lutetium-177 delivers targeted radiation to neoplastic tissues while sparing surrounding normal tissues. This approval provides the radiopharmaceutical infrastructure for multiple targeted radionuclide therapies already authorised or under development in the EU/EEA, including lutetium-177 dotatate for gastroenteropancreatic neuroendocrine tumours and lutetium-177 PSMA for metastatic castration-resistant prostate cancer. The availability of this radiopharmaceutical precursor is essential for nuclear medicine departments offering these increasingly important cancer therapies.
Supemtek received marketing authorisation as a trivalent recombinant influenza vaccine for prevention of influenza in adults and children from nine years of age. This vaccine is manufactured using recombinant DNA technology in insect cell culture rather than embryonated chicken eggs, the production method for most influenza vaccines. Recombinant manufacturing offers several theoretical advantages including elimination of egg adaptation mutations that can reduce vaccine effectiveness, potential for more rapid production scale-up during pandemic scenarios, and avoidance of egg-related contraindications affecting individuals with severe egg allergies. The vaccine complies with World Health Organisation and European Union recommendations for the 2025/2026 Northern Hemisphere influenza season. Given the high influenza activity currently affecting the EU/EEA and the documented mortality burden in older adults during the 2025/2026 season, availability of additional influenza vaccine formulations supporting vaccination programmes is epidemiologically valuable.
Zynyz (retifanlimab) received an extension of indication for treatment of adults with squamous cell carcinoma of the anal canal that cannot be removed surgically and is metastatic or locally recurrent. Squamous cell carcinoma of the anal canal, accounting for approximately 85% of all anal malignancies, has historically lacked specific authorised treatments beyond cytotoxic chemotherapy regimens developed for other squamous cell carcinomas. The disease is aetiologically linked to human papillomavirus infection, particularly HPV-16, and disproportionately affects populations with HIV infection, solid organ transplantation, or other forms of immunosuppression. Retifanlimab is a programmed death receptor-1 inhibitor, a class of immune checkpoint inhibitors that have demonstrated activity across multiple tumour types expressing programmed death-ligand 1. This approval provides the first specifically authorised treatment for advanced or metastatic anal canal squamous cell carcinoma in the EU/EEA, addressing a significant gap in therapeutic options for a disease with poor prognosis in the metastatic setting. For medical oncology services managing gastrointestinal malignancies, this approval enables evidence-based treatment selection for a previously underserved patient population.
Eurneffy (epinephrine) received an extension of indication with a new strength—1 milligram nasal spray solution—indicated for children with body weight 15 to less than 30 kilograms. Eurneffy represents the first emergency treatment for severe allergic reactions administered via nasal spray rather than intramuscular injection, potentially improving treatment accessibility in scenarios where injection administration faces barriers including needle phobia, inadequate training, or hesitation to use autoinjectors. The nasal formulation uses absorption across nasal mucosa to achieve systemic epinephrine concentrations, though onset may differ from intramuscular administration. This approval extends the paediatric indication to include younger children with lower body weights, broadening the population eligible for nasal epinephrine administration during anaphylactic emergencies. For paediatric allergy services and families managing children at risk of anaphylaxis, this provides an alternative administration route, though education regarding appropriate clinical scenarios and complementary rather than replacement positioning relative to intramuscular epinephrine autoinjectors remains important.
The Committee initiated a referral procedure for Tavneos (avacopan) following emerging information raising concerns regarding data integrity in the pivotal clinical trial supporting marketing authorisation. Tavneos is indicated for treatment of adults with severe, active granulomatosis with polyangiitis or microscopic polyangiitis—two rare forms of antineutrophil cytoplasmic antibody-associated vasculitis affecting small and medium-sized blood vessels. The referral was requested by the European Commission under Article 20 of Regulation (EC) No 726/2004, which allows regulatory review when questions arise regarding benefit-risk balance of authorised medicines. Data integrity concerns in pivotal clinical trials represent serious regulatory and ethical issues affecting confidence in evidence supporting marketing authorisations. The referral procedure will assess the nature and extent of data integrity issues, their impact on the interpretation of efficacy and safety results, and implications for the continued marketing authorisation. For rheumatology and nephrology services managing ANCA-associated vasculitis, this creates uncertainty regarding an adjunctive treatment option for severe disease, pending the Committee’s assessment. Healthcare professionals should monitor regulatory communications regarding this referral and its outcomes.
The Committee finalised assessment of an application to extend the indication for Mounjaro (tirzepatide) to include treatment of symptomatic chronic heart failure with preserved ejection fraction in adults with obesity. Mounjaro is currently authorised for obesity management and is used together with diet and physical activity in individuals with body mass index of 30 kilograms per square metre or greater, or body mass index between 27 and 30 kilograms per square metre with weight-related comorbidities including type 2 diabetes, dyslipidaemia, hypertension, or obstructive sleep apnoea. Heart failure with preserved ejection fraction accounts for approximately 50% of heart failure cases, predominantly affects older adults and individuals with obesity, hypertension, and diabetes, and lacks effective pharmacological treatments beyond management of contributing conditions. Although the Committee did not recommend granting a separate therapeutic indication for heart failure with preserved ejection fraction, relevant study data have been incorporated into the medicine’s product information, ensuring healthcare professionals have access to evidence regarding tirzepatide’s effects in adults with chronic heart failure with preserved ejection fraction and obesity. This decision reflects regulatory assessment that the submitted evidence, while informative, did not meet the evidentiary standard required for a specific therapeutic indication. For cardiology and endocrinology services managing the substantial overlap between obesity and heart failure with preserved ejection fraction, the inclusion of study data in product information provides valuable context for treatment decision-making, even in the absence of a formal indication.
Infectious Diseases: Global Perspective
Respiratory and Droplet Transmission
Nipah virus disease emerged as an immediate public health concern during Week 5, with India’s Ministry of Health and Family Welfare confirming two cases in West Bengal state on 27 January 2026. Both confirmed cases are healthcare workers employed at the same hospital in the district of North 24 Parganas, near Kolkata. Media reporting, citing health authorities, indicated a total of five Nipah virus disease cases at the hospital, though only two received laboratory confirmation through official surveillance systems. According to media accounts, both nurses had provided direct patient care to an individual presenting with symptoms consistent with Nipah virus infection, suggesting nosocomial transmission through inadequate infection prevention and control measures during patient management. One nurse reportedly travelled to a village in Nadia district near the Bangladesh border and may have consumed raw date palm sap, a recognised transmission pathway for Nipah virus through contamination of sap collection vessels by bat urine or saliva from infected Pteropus fruit bat reservoir hosts. This exposure history, while reported in media accounts, has not been confirmed through official public health communications. As of 27 January 2026, a total of 196 contacts of the confirmed cases completed testing with negative results, according to India’s Ministry of Health and Family Welfare.
West Bengal has documented previous Nipah virus disease outbreaks in Siliguri in 2001 and Nadia district in 2007, establishing the state as an area with documented viral circulation and appropriate ecological conditions supporting bat reservoir populations. During 2025, India reported four Nipah virus disease cases from Palakkad district (two cases) and Malappuram district (two cases) in Kerala state, with two deaths, both occurring in Palakkad district. The emergence of cases in West Bengal, geographically distant from the Kerala focus, raises questions regarding viral geographic distribution, reservoir host ecology, and surveillance sensitivity across different Indian states.
Nipah virus, classified as Henipavirus nipahense within the family Paramyxoviridae, is a highly pathogenic zoonotic virus first identified during a 1999 outbreak in Malaysia and Singapore. The natural reservoir comprises Pteropus fruit bats distributed across South and Southeast Asia. Human infection occurs through direct contact with infected bats or their excretions, consumption of food contaminated by bat saliva or urine—particularly raw date palm sap collected in vessels that bats may access—contact with infected domestic animals particularly pigs, or person-to-person transmission through direct contact with infected individuals or respiratory secretions. The incubation period ranges from four to 14 days. Clinical manifestations vary from asymptomatic infection or mild influenza-like illness through severe respiratory disease to acute encephalitis. Patients may present with fever, headache, myalgia, and vomiting progressing to altered mental status, seizures, and coma. Respiratory involvement ranges from mild cough to acute respiratory distress syndrome. Case fatality rates vary by outbreak from 40% to 75%, reflecting differences in viral strain virulence, transmission routes, healthcare capacity, and case ascertainment. No specific antiviral treatment or vaccine is available for Nipah virus disease; clinical management is supportive, including mechanical ventilation for respiratory failure and intensive care for encephalitis. The lack of effective therapeutics combined with person-to-person transmission capability and high case fatality rates establish Nipah virus as a Priority Pathogen for Research and Development under the World Health Organisation’s prioritisation framework.
Neighbouring countries initiated precautionary measures following the West Bengal cases. Thailand, Nepal, Cambodia, and other countries bordering or with substantial air traffic connections to India implemented information campaigns and screening protocols for passengers arriving from India at international airports. These measures reflect the recognised potential for international spread through infected travellers during the incubation period before symptom onset. However, the likelihood of exposure to and infection with Nipah virus for EU/EEA citizens travelling to or residing in India remains very low, given the limited number of infections identified to date, the focal geographic distribution of cases, and the specific exposure pathways required for transmission. The most likely route for viral introduction into the EU/EEA would be an infected traveller during the incubation period or early symptomatic phase, though this likelihood is currently very low. Even if importation occurred, the absence of natural reservoir hosts in Europe, combined with robust healthcare infection prevention and control capacity and surveillance systems, would substantially limit transmission potential. Therefore, the overall risk for the EU/EEA population is assessed as very low in the current epidemiological context.
EU/EEA travellers and residents in West Bengal should observe general precautions against zoonotic disease transmission. These include avoiding handling or close contact with domestic or wild animals, avoiding contact with animal excreta, and not consuming raw date palm sap, which may be contaminated by bat saliva or urine during collection. Washing, peeling, and cooking fruits and vegetables before consumption provides general protection against foodborne pathogens. Healthcare workers providing clinical care in areas with Nipah virus circulation should implement standard, contact, and droplet precautions, with consideration of airborne precautions for aerosol-generating procedures, given documented nosocomial transmission in previous outbreaks.
Vector-Borne Transmission
Avian influenza A(H5N1) surveillance in mammals revealed a significant development on 23 January 2026 when authorities in the Netherlands reported detection of antibodies against avian influenza A(H5N1) in milk from a dairy cow at a farm in Friesland province. This represents the first detection of cattle exposure to highly pathogenic avian influenza in the European Union/European Economic Area and only the second country globally, after the United States, to identify serological evidence of infection in domestic cattle. The detection followed investigation of an avian influenza A(H5N1) infection in a domestic cat at the same dairy farm in December 2025. Following the feline case, 20 dairy cattle underwent random sampling on 15 January 2026 with testing for avian influenza A(H5N1) conducted at Wageningen Bioveterinary Research. Diagnostic testing found no active viral shedding in milk samples from any of the 20 cattle, but one cow demonstrated antibodies against avian influenza virus based on enzyme-linked immunosorbent assay and Luminex testing, indicating previous exposure and immune response. The seropositive cow experienced mastitis in mid-December 2025, and milk from this cow was excluded from the human food chain during the period of clinical disease. All milk from the farm undergoes pasteurisation before distribution, a thermal process that inactivates influenza viruses.
Following detection of the seropositive animal, all dairy cattle at the farm underwent sampling on 22 January 2026 with testing for active avian influenza A(H5N1) virus; all results were negative. Serological testing for antibodies against avian influenza virus in the complete herd was ongoing at the time of reporting, with results pending. Currently, no indication exists of active viral circulation within the dairy herd or transmission to other farms in the region. Farm personnel and the attending veterinarian were offered polymerase chain reaction testing and serological testing for A(H5N1) by the Municipal Health Service, with results pending at the time of reporting. None of the exposed individuals reported recent symptoms consistent with influenza virus infection.
The viral isolate from the domestic cat, submitted to the GISAID database on 7 January 2026 with collection date 24 December 2025 and designated A/Domestic cat/Netherlands/25021875-005/2025, belongs to clade 2.3.4.4b, genotype EA2024-DI, subgroup DI.2. All highly pathogenic avian influenza A(H5Nx) viruses detected in avian species in Europe since 2016 belong to clade 2.3.4.4b, and during the 2024–2025 epidemiological year, DI.2 emerged as the most frequent and geographically widespread genotype among highly pathogenic avian influenza A(H5N1) viruses circulating in the region. Phylogenetic analysis positioned the feline isolate within a branch containing other DI.2 strains collected from wild and captive birds in Europe during 2025, including strains from wild birds in the Netherlands. The feline isolate demonstrates one nucleotide difference in the haemagglutinin gene segment compared to avian strains within this phylogenetic branch. Significantly, the isolate acquired the E627K substitution in the PB2 polymerase segment, an amino acid change strongly associated with enhanced viral polymerase activity in mammalian cells. This mutation appears in approximately 47% of mammalian isolates but fewer than 1% of avian isolates, reflecting its role in adaptation to mammalian hosts. The presence of this mutation in the feline isolate raises questions regarding the viral population infecting cattle at the farm and whether similar adaptive mutations are present.
The detection of avian influenza A(H5N1) antibodies in cattle raises important questions regarding mammalian adaptation of highly pathogenic avian influenza viruses and potential for establishment of mammalian reservoir hosts beyond poultry. The United States documented widespread highly pathogenic avian influenza A(H5N1) circulation in dairy cattle beginning in March 2024, with subsequent human infections in farm workers through direct exposure to infected cattle or contaminated environments. All human cases in the United States experienced mild symptoms, primarily conjunctivitis and upper respiratory symptoms, without requiring hospitalisation. Transmission of avian influenza virus via pasteurised milk and dairy products is considered highly unlikely, given that pasteurisation temperatures exceed the thermal inactivation threshold for influenza viruses.
The risk assessment for EU/EEA populations depends on clarification of several uncertainties. The extent of cattle exposure at the affected farm remains unclear pending completion of herd-wide serological testing. Whether the index cat and affected cow were infected from a common environmental source—such as contaminated feed, water, or contact with infected wild birds—or whether cross-species transmission occurred between species on the farm requires investigation. The viral characteristics of isolates from cattle, if virus can be recovered from archived samples, would clarify whether viruses circulating in cattle carry mammalian adaptation markers similar to the feline isolate. With currently available information, the risk from avian influenza A(H5N1) clade 2.3.4.4b viruses currently circulating in Europe is assessed as low for the general population and low to moderate for individuals with occupational or other exposure to infected animals, including cattle, or contaminated environments. Enhanced surveillance, active monitoring and testing of exposed individuals, risk-based testing of symptomatic individuals with animal exposure, and implementation of appropriate personal protective equipment and biosecurity measures for workers in contact with potentially infected animals remain essential public health responses.
Bloodborne and Tissue Transmission
The Marburg virus disease outbreak in Ethiopia was officially declared over on 26 January 2026, following completion of a 42-day period—equivalent to two maximum incubation periods—without detection of new cases since the death of the last laboratory-confirmed case on 14 December 2025. This declaration marks the successful conclusion of Ethiopia’s first documented Marburg virus disease outbreak, which was identified on 14 November 2025.
The outbreak comprised 19 cases (14 laboratory-confirmed and five probable) of Marburg virus disease across four woredas in two regions: Jinka, Malle, and Dasenech woredas in South Ethiopia Regional State, and Hawassa in Sidama Region. Jinka town served as the epidemiological epicentre. The outbreak resulted in 14 deaths (nine among laboratory-confirmed cases and five among probable cases), yielding a case fatality rate of 64.3% among confirmed cases—consistent with historical Marburg virus disease mortality. Five patients recovered from laboratory-confirmed infection, representing a 29.4% recovery rate.
The first recognised case was an adult from Jinka town who developed symptoms on 23 October 2025 and presented to the General Hospital on 24 October 2025 with vomiting, abdominal cramps, and anorexia. Clinical presentation across the case series included sudden-onset fever, myalgia, severe fatigue, headache, diarrhoea, vomiting, and in later disease stages, unexplained haemorrhage—manifestations consistent with filovirus disease pathophysiology. The outbreak investigation revealed subsequent cases among healthcare workers, family contacts, and community members, establishing multiple transmission chains requiring intensive contact tracing and monitoring.
According to the World Health Organisation, a total of 857 listed contacts completed their 21-day monitoring period: 760 contacts in South Ethiopia Regional State and 97 contacts in Sidama Region. Contact tracing and monitoring represent cornerstone interventions for filovirus outbreak control, enabling early case detection, isolation, and interruption of transmission chains. The absence of new cases among this substantial contact cohort through the completion of monitoring provides confidence in outbreak containment.
Response activities included implementation of the cAd3-Marburg vaccine trial, initiated on 8 December 2025 in both affected regions. Ethiopia received 2,500 doses of the candidate vaccine and prioritised healthcare professionals and case contacts for vaccination, implementing a ring vaccination strategy around confirmed cases. This represented the first field deployment of an investigational Marburg virus vaccine in an outbreak context, providing critical data on feasibility, acceptability, and potential effectiveness for future outbreak response. Additionally, monoclonal antibody treatment was implemented for cases, representing experimental therapy given the absence of approved antiviral treatments for Marburg virus disease. Community-level monitoring, contact tracing, and house-to-house case finding were intensified to detect additional cases. International partners including the World Health Organisation, Africa Centres for Disease Control and Prevention, and epidemic response organisations provided technical and logistical support.
In December 2025, during Ethiopia’s outbreak, three deaths reported in South Sudan raised concern for possible transboundary spread, and an alert was issued in Wajaale, a major border city in the Somaliland region. Neighbouring countries including South Sudan, Kenya, and Somalia intensified preparedness efforts including enhancement of surveillance systems, training of healthcare workers in infection prevention and control, and establishment of isolation capacity for suspected cases.
Marburg virus disease, caused by Marburg marburgvirus, is a severe haemorrhagic fever with case fatality rates historically reaching 88% in some outbreaks. The virus belongs to the family Filoviridae, genus Marburgvirus, closely related to Ebola virus. Egyptian fruit bats (Rousettus aegyptiacus) serve as the natural reservoir host, with human infections typically initiated through exposure to mines or caves inhabited by infected bat colonies. Human-to-human transmission occurs through direct contact with blood, secretions, organs, or other bodily fluids of infected individuals, and with surfaces and materials contaminated with these fluids. The incubation period ranges from three to 21 days, typically five to 10 days. Clinical disease begins abruptly with high fever, severe headache, and malaise, progressing to severe watery diarrhoea, abdominal pain, nausea, and vomiting by days three to five. Haemorrhagic manifestations including bleeding from venepuncture sites, gastrointestinal bleeding, and mucosal bleeding typically appear by days five to seven in fatal cases. Case fatality depends on viral strain virulence, transmission intensity, timing of supportive care initiation, and healthcare infrastructure capacity. No specific antiviral treatment or approved vaccine exists for Marburg virus disease; clinical management is supportive, including fluid and electrolyte replacement, maintenance of oxygen status and blood pressure, and treatment of specific complications.
The successful containment of Ethiopia’s outbreak demonstrates the effectiveness of rapid outbreak response, comprehensive contact tracing, healthcare worker protection through infection prevention and control, community engagement, and international coordination. The integration of investigational vaccines and therapeutics into outbreak response represents an important evolution in filovirus outbreak management, building on experience from West African Ebola outbreak responses. The declaration of outbreak’s end does not eliminate risk of future zoonotic transmission events, given the continued presence of reservoir bat populations in the region and human activities bringing populations into contact with bat habitats.
Fecal-Oral Transmission
Global cholera surveillance documented continued widespread transmission across Africa, Asia, and the Middle East during the reporting period. Since 24 December 2025 and as of 28 January 2026, 11,965 new cholera cases including 126 deaths were reported globally. The five countries reporting the highest case counts were the Democratic Republic of the Congo (4,522 cases), Afghanistan (3,029 cases), Yemen (1,144 cases), Mozambique (896 cases), and India (878 cases). The five countries reporting the most deaths were the Democratic Republic of the Congo (89 deaths), the Philippines (14 deaths), India (six deaths), Yemen (five deaths), and Côte d’Ivoire (four deaths).
Since 1 January 2026 and as of 27 January 2026, eight countries reported 1,203 cholera cases including seven deaths: Angola (152 cases, two deaths), Burundi (23 cases), Ethiopia (15 cases), Malawi (12 cases, two deaths), Mozambique (896 cases, three deaths), Namibia (18 cases), Somalia (82 cases), and Zambia (five cases). This represents an 88% decrease compared to the 10,043 cases including 32 deaths reported during the equivalent period in 2025 across all reporting countries globally. However, interpretation requires caution given reporting delays and the January timing, when many surveillance systems experience reduced reporting intensity following year-end transitions and holiday periods.
In southern Africa, Mozambique’s 896 cases since 1 January 2026 indicate sustained transmission, likely driven by inadequate water, sanitation, and hygiene infrastructure, seasonal rainfall affecting water sources, and population displacement. Angola’s emergence with 152 cases represents renewed cholera transmission requiring investigation of water supply contamination, sanitation breakdowns, or population movements. Malawi, Namibia, and Zambia each reported small case numbers suggesting either successful outbreak control or early-phase transmission requiring vigilance.
Afghanistan continues experiencing intense cholera transmission with 3,029 cases reported between 8 December 2025 and 28 December 2025. Afghanistan’s ongoing humanitarian crisis, characterised by widespread displacement, collapse of water and sanitation infrastructure, malnutrition, and limited healthcare access, creates optimal conditions for cholera transmission. Cumulative 2025 data through 28 December documented 164,820 cases and 80 deaths, nearly matching the 175,262 cases and 88 deaths reported during the equivalent 2024 period, demonstrating sustained endemic transmission at crisis levels.
Yemen reported 1,144 new cases including five deaths between 1 December 2025 and 28 December 2025. Yemen’s protracted conflict has devastated water and sanitation infrastructure, displaced millions, and created widespread acute malnutrition, establishing conditions for cholera hyperendemicity. Cumulative 2025 data through 23 December documented 93,496 cases and 248 deaths, representing a 64% decrease compared to the 260,552 cases and 879 deaths reported during 2024, though Yemen continues experiencing one of the world’s largest cholera epidemics.
In the Democratic Republic of the Congo, 4,522 new cases including 89 deaths were reported between 24 December 2025 and 31 December 2025, maintaining the extraordinarily high transmission intensity characterising this outbreak. Cumulative 2025 data through 31 December documented 71,646 cases and 2,028 deaths, representing a 150% increase compared to the 28,618 cases and 385 deaths reported through November 2024. The Democratic Republic of the Congo’s epidemic reflects a combination of deteriorating water and sanitation infrastructure, population displacement due to armed conflict, inadequate healthcare capacity, and breakdown of cholera prevention and control programmes. The extremely high case fatality rate among reported deaths suggests delayed presentation to healthcare facilities, limited access to oral rehydration solution and intravenous fluid resuscitation, and potentially high prevalence of severe acute malnutrition increasing cholera severity.
The global cholera situation reflects the persistent gap between oral cholera vaccine supply and demand. The Global Oral Cholera Vaccine Stockpile, managed by the International Coordinating Group on Vaccine Provision, has implemented temporary suspension of the standard two-dose vaccination regimen in favour of single-dose campaigns to extend coverage across more populations at risk. While this decision maximises short-term coverage, single-dose protection wanes more rapidly than two-dose regimens, potentially requiring booster campaigns that further strain limited vaccine supplies. Expansion of oral cholera vaccine manufacturing capacity represents a critical priority for global cholera control.
For EU/EEA populations, cholera risk remains low even during travel to affected regions, provided travellers follow water, sanitation, and food hygiene precautions. These include consuming only boiled or bottled water, avoiding ice unless made from safe water, eating thoroughly cooked food served hot, avoiding raw vegetables and fruits unless peeled by the traveller, and practising frequent handwashing with soap and safe water. Oral cholera vaccine is recommended for higher-risk travellers including emergency response workers, healthcare personnel working in outbreak settings, and individuals travelling to areas experiencing active transmission who anticipate limited access to safe water and sanitation. The vaccine is not recommended for typical tourists staying in standard accommodations.
Contact and Sexual Transmission
Bacillus cereus contamination of infant formula emerged as a significant food safety concern during December 2025 and continued into January 2026, with ongoing product recalls across multiple countries including EU/EEA Member States. The contamination involved detection of cereulide, the emetic toxin produced by specific Bacillus cereus strains, in several infant nutrition products spanning different batches, product formulations, and brand names. The precautionary recall, initiated in December 2025 and continuing through January 2026, followed company quality control testing that identified cereulide presence. Root cause analysis by the manufacturer identified arachidonic acid oil—an ingredient added to infant formula to provide long-chain polyunsaturated fatty acids supporting infant neurodevelopment—as the contamination source.
Bacillus cereus comprises a group of Gram-positive, spore-forming, aerobic or facultatively anaerobic bacteria widely distributed in soil and environmental reservoirs. The bacterium produces two distinct toxin syndromes. The diarrhoeal syndrome, mediated by enterotoxins produced during vegetative growth in the small intestine, typically manifests 8 to 16 hours after ingestion with abdominal cramps and watery diarrhoea. The emetic syndrome, mediated by cereulide—a cyclic dodecadepsipeptide synthesised during bacterial growth in food—manifests within one to six hours after ingestion with nausea and vomiting, occasionally accompanied by abdominal cramps and diarrhoea. Cereulide demonstrates extraordinary thermostability, remaining active after exposure to 121°C for 90 minutes, substantially exceeding the thermal inactivation conditions for most bacterial toxins. This thermostability enables cereulide persistence through food processing conditions that eliminate vegetative bacterial cells and many other toxins.
Cereulide acts as a potassium ionophore, disrupting mitochondrial function and cellular ion gradients. In severe cases, particularly involving high toxin doses or vulnerable populations, cereulide causes fulminant hepatic failure characterised by massively elevated transaminases, coagulopathy, hypoglycaemia, and hyperammonaemia progressing to hepatic encephalopathy. Fatalities have been documented, particularly in young children. The toxin also demonstrates cardiotoxicity, potentially causing arrhythmias. Neonates and young infants may be particularly vulnerable to cereulide toxicity given their developing hepatic detoxification capacity, limited metabolic reserves, and dependence on formula feeding without dietary diversity that might dilute toxin exposure.
European Centre for Disease Prevention and Control received reports of diarrhoea in infants following consumption of recalled products. One laboratory-confirmed case involved detection of cereulide in a faecal sample from a young infant using mass spectrometry, a highly specific analytical method for cereulide quantification. The infant had consumed milk prepared from a recalled batch of formula and presented with vomiting and diarrhoea, achieving favourable clinical outcome without reported complications. This case provides strong evidence linking product consumption to clinical illness, though the rarity of cereulide detection in clinical specimens limits understanding of disease burden. Additionally, formula sampled from an unopened container from a recalled batch, collected from the household of an infant reporting symptoms after consumption, tested positive for cereulide toxin, providing product-level confirmation of contamination.
The affected products experienced wide distribution across EU/EEA countries and globally, creating substantial exposure opportunity for infants consuming these formulations. National food safety authorities initiated product withdrawals and recalls, advised consumers to discontinue use of affected products, and implemented enhanced surveillance for potential cases. The likelihood of exposure to contaminated formula batches was initially moderate to high for infants consuming the affected brands and formulations, though ongoing recalls progressively reduced exposure likelihood. The impact of potential cereulide exposure varies by infant age, with neonates and infants younger than six months potentially experiencing higher risk of severe manifestations including dehydration, electrolyte disturbances, and hepatotoxicity, compared to older infants with more developed hepatic metabolism and ability to tolerate fluid losses. Therefore, the overall risk to infants less than one year in the EU/EEA was initially assessed as moderate during the height of exposure, decreasing as recall completion progressed.
This incident highlights critical food safety challenges in infant formula manufacturing, where products must achieve microbiological safety while supporting optimal infant nutrition. The thermostability of cereulide presents particular challenges, as standard pasteurisation and sterilisation processes that eliminate bacterial cells do not inactivate pre-formed toxin. Prevention requires controlling bacterial growth in ingredients throughout the supply chain, particularly ingredients like vegetable oils that may support bacterial growth if contaminated and held at temperatures permitting sporulation and toxin production. Enhanced supplier qualification, ingredient testing for cereulide, and process validation to prevent cross-contamination represent essential control measures.
Infectious Diseases: European Union/European Economic Area
Respiratory and Droplet Transmission
Influenza activity across the EU/EEA remained elevated throughout Week 3 of 2026—the most recent week with comprehensive surveillance data available—with early indications of renewed intensification following a four-week period of declining trends from the initial epidemic peak in late 2025. According to the European Respiratory Virus Surveillance Summary, 20 of 23 reporting countries continued experiencing widespread geographic influenza transmission, defined as influenza activity affecting multiple regions within countries. Influenza virus detections in sentinel primary care surveillance yielded a pooled test positivity of 37%, with median country-level positivity of 40% and interquartile range of 23% to 55%. This sustained high positivity indicates continued intense viral circulation despite the four-week decline following the late-2025 peak. Sentinel hospital surveillance for severe acute respiratory infection documented influenza test positivity of 25%, with median country-level positivity of 18% and interquartile range of 14% to 38%, indicating substantial proportions of hospitalised patients with severe respiratory illness have influenza virus infection.
The renewed increase in primary care consultations for influenza-like illness and acute respiratory infection, following the four-week declining trend, predominantly affects children aged five to 14 years, suggesting either renewed transmission within school-age populations or shifting age-specific epidemic dynamics as older age groups develop immunity through infection or vaccination. Conversely, overall influenza-associated hospital admissions continued declining compared to previous weeks, though recent data demonstrated increases specifically among hospitalised children aged five to 14 years, mirroring the primary care pattern. This age-specific increase among hospitalised children warrants monitoring to assess whether paediatric hospital admissions will intensify in coming weeks, potentially straining paediatric hospital capacity.
Adults aged 65 years and above continue accounting for the highest absolute numbers of influenza-associated hospital admissions, intensive care unit admissions, and in-hospital deaths during the 2025/2026 season. This age distribution reflects the well-established pattern of severe influenza outcomes concentrating in older adults due to immunosenescence, multimorbidity, and reduced physiological reserve. The substantial mortality burden in this age group during an influenza season beginning three to four weeks earlier than the previous two seasons underscores the importance of achieving high influenza vaccination coverage in older adults and other high-risk populations before seasonal epidemic onset.
Virological surveillance indicates influenza A(H3N2) remains the dominant circulating subtype, representing 72% of typed influenza A viruses during Week 4 of 2026. Influenza A(H1N1)pdm09 accounts for 28% of typed influenza A viruses. Influenza B viruses represent less than 1% of influenza detections, indicating minimal influenza B circulation during the current epidemic period. Among genetically characterised influenza A(H3N2) viruses, subclade 2a.3a.1(K) accounts for 92% of sequenced viruses, with subclades 2a.3a.1(J.2), 2a.3a.1(J.2.4), and 2a.3a.1(J.2.2) representing small proportions. Among influenza A(H1N1)pdm09 viruses, subclade 5a.2a.1(D.3.1) represents 99% of sequenced viruses. Among the small number of influenza B viruses, B/Victoria lineage viruses predominate.
Early estimates of seasonal influenza vaccine effectiveness for the 2025/2026 season, published by the European Centre for Disease Prevention and Control on 19 December 2025, align with estimates published by other countries for influenza A(H3N2) viruses. These interim estimates provide reassurance that vaccine strain selection for the Northern Hemisphere 2025/2026 season achieved reasonable antigenic match to circulating viruses, though final season-end vaccine effectiveness estimates will provide definitive assessment. Given the substantial mortality burden in older adults during the current season, maximising vaccination coverage in this population and other high-risk groups remains a public health priority, even though vaccine effectiveness against influenza A(H3N2) typically demonstrates lower magnitude compared to effectiveness against influenza A(H1N1)pdm09.
Respiratory syncytial virus circulation is elevated and continues increasing in most EU/EEA countries. This season’s RSV epidemic is occurring several weeks later than the previous two seasons, following a pattern of substantial inter-seasonal variability in RSV epidemic timing observed across multiple Northern Hemisphere regions. RSV test positivity in sentinel primary care surveillance reached 10%, with median country-level positivity of 7.2% and interquartile range of 4.5% to 12%. Sentinel hospital surveillance documented RSV test positivity of 15%, with median country-level positivity of 12% and interquartile range of 8% to 20%. Hospital admissions associated with RSV are rising in most reporting countries, primarily affecting children aged under five years, particularly infants aged under six months who experience the highest rates of RSV-associated hospitalisation and severe disease. Among genotyped RSV strains, RSV-A accounts for 50% and RSV-B accounts for 50% of typed detections, indicating co-circulation of both major RSV subtypes.
The delayed onset of this season’s RSV epidemic relative to recent years has implications for immunisation programmes utilising long-acting monoclonal antibodies for RSV prevention in infants. Programmes administering nirsevimab—a long-acting monoclonal antibody targeting the RSV fusion protein—typically aim to achieve protection before seasonal epidemic onset. The shifted epidemic timing may have resulted in better temporal alignment between monoclonal antibody administration and peak transmission intensity in countries that administered nirsevimab during autumn 2025. Evaluation of nirsevimab effectiveness during the current season will provide important data on real-world protection and inform optimal timing for future RSV prevention programmes.
SARS-CoV-2 circulation remains low across the EU/EEA in all age groups. SARS-CoV-2 test positivity in sentinel primary care surveillance measured 2.9%, with median country-level positivity of 3% and interquartile range of 0.3% to 6.2%. Sentinel hospital surveillance documented SARS-CoV-2 test positivity of 2.5%, with median country-level positivity of 1% and interquartile range of 0% to 2.8%. The number of hospitalisations due to SARS-CoV-2 is currently limited compared to influenza and RSV, indicating SARS-CoV-2 is not a major contributor to current healthcare system burden. Among sequenced SARS-CoV-2 viruses, the XEC recombinant variant accounts for 48% of detections (median distribution across reporting countries 27% to 50%), NB.1.8.1 accounts for 23% of detections (median 20% to 27%), and BA.2.86 descendant lineages account for small proportions.
EuroMOMO, the European mortality monitoring system, reports substantially elevated all-cause mortality levels across participating countries, primarily driven by increased mortality in several countries among age groups above 65 years. Excess mortality during winter months typically reflects contributions from influenza, RSV, SARS-CoV-2, other respiratory pathogens, cardiovascular events exacerbated by cold temperature or respiratory infections, and healthcare system strain. The concentration of excess mortality in populations aged 65 years and above aligns with the observed influenza epidemiology, where older adults experience the highest rates of influenza-associated hospitalisation and death. The substantial excess mortality during a season characterised by early influenza epidemic onset and high influenza A(H3N2) circulation—a subtype historically associated with greater severity in older adults compared to influenza A(H1N1)pdm09—underscores the continued substantial public health burden of seasonal influenza despite available interventions.
The 2025/2026 influenza season’s early onset, occurring three to four weeks ahead of the previous two seasons, caught some healthcare systems and vaccination programmes during vaccine delivery, potentially resulting in lower proportions of at-risk populations protected before epidemic onset. The convergence of high influenza activity, increasing RSV circulation, and elevated all-cause mortality creates substantial healthcare system pressure, particularly affecting hospital capacity for older adults requiring admission for respiratory complications, cardiac decompensation, or other influenza-associated severe outcomes.
Public health priorities include sustaining influenza vaccination delivery to protect individuals not yet vaccinated, maintaining healthcare system surge capacity for respiratory illness, implementing appropriate infection prevention and control in healthcare settings to prevent nosocomial transmission, and ensuring availability of influenza antiviral medications for treatment of severe cases and post-exposure prophylaxis in high-risk settings. Healthcare providers should maintain high index of suspicion for influenza in patients presenting with acute febrile respiratory illness, particularly in older adults and other high-risk populations, and initiate antiviral treatment promptly based on clinical and epidemiological judgment without awaiting laboratory confirmation, given that early antiviral treatment—ideally within 48 hours of symptom onset—provides greatest benefit.
Infectious Diseases: Bulgaria
Respiratory and Droplet Transmission
Varicella surveillance during Week 5 documented 558 cases, representing a 13.2% decline from the 632 cases reported during Week 4 and continuing the downward trajectory from the 650-case peak reported in Week 3. Varicella cases were distributed across 27 of 28 Bulgarian regions, with highest absolute case counts in Sofia-capital (122 cases), Plovdiv (58 cases), Haskovo (48 cases), Varna (60 cases), Burgas (40 cases), and Blagoevgrad (35 cases). The geographic distribution reflects population density, with larger urban centres accounting for higher absolute case counts. Since the beginning of 2026, Bulgaria registered 2,885 cumulative varicella cases compared to 3,343 cases during the equivalent period in 2025, representing a 13.7% decline year-over-year. This decrease may reflect cohort effects from previous epidemic years, natural immunity accumulation in susceptible age groups, or potentially increased varicella vaccination coverage, though Bulgaria’s varicella vaccination coverage data require examination to assess programmatic impact.
Varicella, caused by varicella-zoster virus, a neurotropic alphaherpesvirus of the family Herpesviridae, typically affects children aged one to nine years, manifesting as acute febrile illness with characteristic pruritic vesicular rash progressing through stages of macules, papules, vesicles, and crusting. Transmission occurs via respiratory droplets or direct contact with vesicular fluid from skin lesions. The virus establishes latency in dorsal root ganglia following primary infection, with reactivation as herpes zoster occurring decades later, particularly in immunocompromised individuals and adults over 50 years. Varicella vaccination, incorporated into national immunisation schedules in many countries, has substantially reduced varicella incidence where high coverage is achieved. Bulgaria introduced varicella vaccination into its recommended schedule, though coverage levels and vaccine uptake patterns influence population-level impact.
COVID-19 surveillance documented 36 laboratory-confirmed cases during Week 5, representing minimal change from the 37 cases reported during Week 4. Since the beginning of 2026, Bulgaria recorded 215 cumulative COVID-19 cases compared to 175 cases during the equivalent period in 2025, representing a 23% year-over-year increase. However, interpretation requires caution given substantial changes in testing strategies, surveillance systems, and healthcare-seeking behaviour between 2025 and 2026. Bulgaria, like other European countries, transitioned from intensive universal surveillance during the acute pandemic phase toward sentinel surveillance and testing focused on hospitalised patients and high-risk populations, substantially reducing case ascertainment of mild or asymptomatic infections. The 36 weekly cases likely represent severe fraction requiring hospitalisation or testing through sentinel systems rather than comprehensive community transmission burden. SARS-CoV-2 continues circulating endemically across Bulgaria and Europe, with periodic fluctuations in transmission intensity influenced by waning population immunity, emergence of immune-escape variants, seasonal factors favouring respiratory virus transmission, and population behaviour affecting contact rates.
Scarlet fever surveillance documented 66 cases during Week 5, a 17.5% decline from the 80 cases reported during Week 4 and maintaining a relatively stable trajectory following the early-2026 peak. Cases distributed across 18 regions, with highest counts in Sofia-capital (16 cases), Plovdiv (13 cases), and Varna (6 cases). Since the beginning of 2026, Bulgaria registered 279 cumulative scarlet fever cases compared to 484 cases during the equivalent period in 2025, representing a 42.4% decrease year-over-year. This substantial decline warrants attention to assess whether it reflects true reduction in group A Streptococcus pyogenes transmission, changes in healthcare-seeking behaviour or clinical diagnosis patterns, or other surveillance-related factors.
Scarlet fever manifests as a toxin-mediated syndrome caused by group A Streptococcus pyogenes strains producing streptococcal pyrogenic exotoxins, most commonly erythrogenic toxin. The disease typically affects children aged five to 15 years, presenting with acute pharyngitis, fever, and characteristic erythematous rash with sandpaper texture, circumoral pallor, and strawberry tongue. The rash appears within 12 to 48 hours of fever onset, beginning on the trunk and spreading to extremities, sparing palms and soles, and desquamating during convalescence. While scarlet fever typically follows a benign clinical course with appropriate antibiotic treatment, group A Streptococcus pyogenes can cause severe invasive disease including bacteraemia, necrotising fasciitis, and streptococcal toxic shock syndrome, as well as post-infectious sequelae including acute rheumatic fever and post-streptococcal glomerulonephritis. The decline in scarlet fever notifications during early 2026 contrasts with increases in invasive group A Streptococcus disease reported in some European countries during recent years, highlighting the importance of monitoring both non-invasive and invasive manifestations of group A streptococcal infection.
Fecal-Oral Transmission
Gastroenteritis and enterocolitis surveillance documented 101 cases during Week 5, representing a 14.4% decline from the 118 cases reported during Week 4. Cases were distributed across 23 regions, with highest counts in Varna (20 cases), Plovdiv (11 cases), and Sofia-capital (11 cases). Since the beginning of 2026, Bulgaria registered 650 cumulative gastroenteritis cases, identical to the 650 cases reported during the equivalent period in 2025, indicating stable endemic baseline transmission. This stability suggests consistent levels of foodborne, waterborne, and person-to-person transmission of enteric pathogens during the winter period, when norovirus, rotavirus, and other viral agents typically dominate acute gastroenteritis aetiology.
Acute gastroenteritis encompasses a broad syndrome caused by diverse bacterial, viral, and parasitic pathogens. Viral agents—particularly norovirus, rotavirus, adenovirus, and astrovirus—predominate in community-acquired acute gastroenteritis, especially during winter months. Bacterial causes include Salmonella, Campylobacter, Shigella, enterotoxigenic and enterohaemorrhagic Escherichia coli, and Yersinia. Clinical presentation typically includes acute onset of diarrhoea with variable accompanying features including nausea, vomiting, abdominal cramping, fever, and systemic symptoms. Most cases are self-limited, resolving within days without specific antimicrobial therapy. Management focuses on oral rehydration, with intravenous fluid replacement reserved for severe dehydration. Populations at highest risk for severe outcomes include young children, older adults, and immunocompromised individuals. The stable gastroenteritis burden during early 2026 indicates that while specific etiological agents show variation—with campylobacteriosis dramatically increasing and rotavirus substantially decreasing, as discussed below—overall gastroenteritis burden remains within expected endemic range.
Rotavirus gastroenteritis surveillance documented 13 laboratory-confirmed cases during Week 5, maintaining a stable low level following the decline from early January peaks. Since the beginning of 2026, Bulgaria recorded 54 cumulative rotavirus cases compared to 123 cases during the equivalent period in 2025, representing a 56.1% decline year-over-year. This substantial decrease likely reflects expanding rotavirus vaccination coverage in Bulgaria. Rotavirus vaccines—both the pentavalent human-bovine reassortant vaccine and the monovalent human attenuated vaccine—demonstrate high effectiveness in preventing severe rotavirus gastroenteritis requiring hospitalisation. Introduction of rotavirus vaccination into national immunisation programmes in countries worldwide has resulted in dramatic reductions in rotavirus-associated hospitalisations, emergency department visits, and healthcare costs. Bulgaria’s rotavirus vaccination programme, introduced in recent years, appears to be achieving population-level impact.
Rotavirus, a non-enveloped double-stranded RNA virus of the family Reoviridae, represents the leading cause of severe acute dehydrating gastroenteritis in unvaccinated infants and young children globally. The virus infects small intestinal enterocytes, causing villous atrophy and malabsorption, resulting in severe watery diarrhoea, vomiting, fever, and rapid dehydration. Infants and children aged six months to two years experience highest severe disease rates. Transmission occurs via fecal-oral route through person-to-person contact, contaminated surfaces and fomites, and potentially aerosolised droplets. The virus demonstrates remarkable environmental stability and low infectious dose. Prior to vaccine introduction, rotavirus caused nearly universal infection by age five, with most children experiencing multiple infections of decreasing severity. The substantial decline in rotavirus cases during 2026 represents a significant public health achievement, reducing paediatric hospitalisations, healthcare costs, and parental work absences due to childcare for ill children.
Campylobacteriosis surveillance documented 14 laboratory-confirmed cases during Week 5, doubling the seven cases reported during Week 4 and representing the highest weekly count since comprehensive surveillance implementation. Since the beginning of 2026, Bulgaria recorded 44 cumulative campylobacteriosis cases compared to just 15 cases during the equivalent period in 2025, representing a 193% year-over-year increase. This dramatic surge requires urgent investigation to identify sources, transmission pathways, and risk factors. Campylobacteriosis demonstrates strong seasonality in temperate climates, with peak incidence during warmer months when foodborne transmission intensifies through undercooking of poultry, cross-contamination during food preparation, and temperature abuse of food storage. However, the current surge is occurring during winter months—outside the typical seasonal peak—suggesting potential outbreak scenarios including contaminated food products distributed across multiple regions, contaminated water sources, or point-source exposures at specific food establishments.
Campylobacter species, particularly Campylobacter jejuni and Campylobacter coli, are Gram-negative spiral or curved bacilli representing the most common bacterial cause of acute gastroenteritis in many high-income countries. The bacteria colonise the intestinal tracts of diverse animal species, particularly poultry, cattle, pigs, and wild birds, without causing disease in these reservoir hosts. Human infection occurs primarily through consumption of undercooked poultry, unpasteurised milk, contaminated water, or cross-contamination from raw poultry to ready-to-eat foods during food preparation. The incubation period ranges from one to seven days, typically two to five days. Clinical presentation includes acute onset of diarrhoea—often bloody with inflammatory character—accompanied by abdominal cramping, fever, nausea, and sometimes vomiting. Most cases resolve spontaneously within one week without antimicrobial treatment. Severe cases may require antibiotic therapy, though increasing fluoroquinolone and macrolide resistance in Campylobacter populations complicates treatment. Post-infectious complications include reactive arthritis affecting one to five percent of cases, and Guillain-Barré syndrome—an acute immune-mediated peripheral neuropathy—affecting approximately one in 1,000 cases, typically developing two to three weeks after acute gastroenteritis onset.
The 193% year-over-year increase in campylobacteriosis demands immediate epidemiological investigation including case interviews to identify common food exposures, restaurant patronage, or other shared risk factors; traceback investigations of implicated food products to identify contamination sources; inspection of food establishments frequented by multiple cases; and microbiological testing of suspect food products, water sources, and environmental samples. Whole-genome sequencing of clinical isolates from cases may identify genetic relatedness indicating common-source outbreak versus sporadic unrelated cases coincidentally clustered in time. Public health interventions may include food recalls if contaminated products are identified, temporary closure of food establishments with sanitation violations, public health advisories regarding safe food handling practices, and enhanced surveillance to detect additional cases.
Salmonellosis surveillance documented 10 laboratory-confirmed cases during Week 5, representing a single-case increase from the nine cases reported during Week 4 and maintaining a stable endemic baseline. Cases distributed across seven regions. Since the beginning of 2026, Bulgaria recorded 55 cumulative salmonellosis cases compared to 46 cases during the equivalent period in 2025, representing a 20% year-over-year increase. While this increase is proportionally smaller than the campylobacteriosis surge, the absolute increase of nine cases warrants monitoring to assess whether salmonellosis transmission is intensifying or whether this represents normal stochastic variation around endemic baseline.
Non-typhoidal Salmonella serovars cause acute gastroenteritis through foodborne and occasionally waterborne transmission. Reptiles and amphibians kept as pets represent another important transmission source, particularly for young children who handle these animals and subsequently engage in hand-to-mouth behaviour without adequate handwashing. Contaminated foods frequently implicated in salmonellosis include poultry, eggs and egg-containing products, raw milk and dairy products, beef, pork, fresh produce contaminated through irrigation water or food handler transmission, and spices. The incubation period ranges from six to 72 hours, typically 12 to 36 hours. Clinical presentation includes acute onset of diarrhoea, abdominal cramping, fever, nausea, and sometimes vomiting. Bacteraemia develops in approximately five percent of cases, particularly affecting infants, older adults, and immunocompromised individuals. Extraintestinal focal infections may involve any organ system but particularly affect vascular endothelium—with mycotic aneurysms as a severe complication in older adults with atherosclerotic vascular disease—bone and joints, and meninges. Most immunocompetent individuals recover without antimicrobial treatment within five to seven days. Antibiotic therapy is reserved for severe cases, bacteraemia, extraintestinal infections, and patients at high risk for invasive disease including infants under three months, adults over 50 years, and immunocompromised individuals.
Dysentery surveillance documented one laboratory-confirmed case of shigellosis during Week 5, the first case reported since early January. The case represents sporadic transmission, likely through person-to-person contact or foodborne exposure. Since the beginning of 2026, Bulgaria recorded two cumulative shigellosis cases compared to one case during the equivalent period in 2025. Given the small absolute numbers, this represents expected endemic-level activity.
Shigella species—Shigella dysenteriae, Shigella flexneri, Shigella boydii, and Shigella sonnei—are Gram-negative enteroinvasive bacteria causing bacillary dysentery through invasion and destruction of colonic epithelium. The disease demonstrates extraordinary transmissibility with infectious doses as low as 10 to 100 organisms, enabling efficient person-to-person spread via fecal-oral route, particularly in settings with inadequate sanitation and hygiene. Foodborne and waterborne transmission also occurs. The incubation period ranges from one to three days. Clinical presentation includes acute onset of frequent small-volume stools containing blood and mucus, severe abdominal cramping and tenesmus, and fever. Complications include dehydration, toxic megacolon, seizures in young children, haemolytic uremic syndrome particularly with Shigella dysenteriae serotype 1, and reactive arthritis. Antibiotic treatment shortens illness duration and reduces faecal shedding. However, Shigella demonstrates concerning antimicrobial resistance patterns globally, including extensive drug resistance to multiple antibiotic classes and emerging resistance to extended-spectrum cephalosporins and azithromycin.
Escherichia coli enteritis surveillance documented two laboratory-confirmed cases during Week 5, representing a 71.4% decline from the seven cases reported during Week 4. Since the beginning of 2026, Bulgaria recorded 20 cumulative cases compared to 18 cases during the equivalent period in 2025. The decline following the Week 4 elevation suggests resolution of a transient cluster or outbreak.
Pathogenic Escherichia coli strains causing gastroenteritis are classified into multiple pathotypes based on virulence mechanisms: enterotoxigenic E. coli producing heat-labile and heat-stable toxins, enteroaggregative E. coli adhering to intestinal mucosa in aggregative patterns, enteropathogenic E. coli causing attaching-and-effacing lesions, enteroinvasive E. coli invading colonic epithelium similar to Shigella, and Shiga toxin-producing E. coli producing cytotoxic Shiga toxins. Shiga toxin-producing E. coli, particularly serotype O157:H7 and other Shiga toxin-producing serotypes, cause haemorrhagic colitis manifesting as severe bloody diarrhoea and abdominal cramping. The most serious complication is haemolytic uremic syndrome, characterised by microangiopathic haemolytic anaemia, acute renal failure, and thrombocytopenia, affecting approximately five to ten percent of Shiga toxin-producing E. coli cases, particularly children under five years and older adults. Antibiotic treatment of Shiga toxin-producing E. coli infections is contraindicated as it may increase haemolytic uremic syndrome risk through enhanced Shiga toxin release. Bulgaria’s surveillance system distinguishes coliform enteritis cases, though virulence characterisation requires molecular or culture-based methods to classify pathotypes and guide public health responses appropriately.
Bloodborne and Tissue Transmission
Acute viral hepatitis surveillance documented 43 laboratory-confirmed cases during Week 5, representing a 19.4% increase from the 36 cases reported during Week 4 and continuing the extraordinarily elevated notification rate characterising early 2026. Cases were distributed across 22 regions, with highest counts in Plovdiv (11 cases), Kardzhali (six cases), Varna (four cases), Dobrich (four cases), and Sofia-capital (four cases). The geographic distribution, affecting 22 of 28 Bulgarian regions, suggests widespread transmission rather than focal outbreak in a single region. Since the beginning of 2026, Bulgaria recorded 185 cumulative acute viral hepatitis cases compared to 62 cases during the equivalent period in 2025, representing a 198% increase year-over-year—an extraordinary surge demanding urgent public health investigation and response.
This near-tripling of acute viral hepatitis notifications within five weeks compared to the previous year’s baseline represents one of the most significant epidemiological signals in Bulgaria’s Week 5 surveillance data. The magnitude and rapidity of increase, combined with the broad geographic distribution, raises multiple urgent questions regarding aetiology, transmission pathways, risk populations affected, and public health response requirements. The surveillance data reported by Bulgaria’s National Center of Infectious and Parasitic Diseases document cases as acute viral hepatitis without virological characterisation specifying hepatitis A, B, C, D, or E aetiology, limiting aetiological inference.
However, the epidemiological pattern—winter seasonality, rapid increase, broad geographic distribution—suggests several potential scenarios. First, hepatitis A transmission may be occurring through foodborne or waterborne exposure to faecally contaminated food products or water sources. Hepatitis A virus demonstrates marked seasonality in temperate climates with winter-spring peaks when transmission intensifies through contaminated food products—particularly fresh produce, shellfish, or frozen foods contaminated during processing—or person-to-person spread in households, childcare settings, and other close-contact environments. Bulgaria has documented hepatitis A outbreaks associated with contaminated food products in previous years, and the country’s hepatitis A vaccination coverage in childhood, while improving, may leave substantial susceptible populations at risk. Second, hepatitis E virus transmission could be increasing through consumption of undercooked pork products or game meat. Hepatitis E virus genotype 3, endemic in Europe, primarily transmits through zoonotic foodborne exposure to infected pork, wild boar, or deer products. Hepatitis E demonstrates winter seasonality in some European countries and can cause large outbreaks. Third, hepatitis B or hepatitis C transmission could be increasing through injection drug use, unsafe medical procedures, or other parenteral exposures. However, the rapid increase and winter timing make this scenario less likely as primary driver, though contributory role cannot be excluded. Fourth, imported cases from international travellers visiting hepatitis A-endemic regions could be contributing, though this would not explain the magnitude of increase unless multiple importation events seeded secondary transmission chains.
Hepatitis A virus, a non-enveloped positive-sense single-stranded RNA virus of the family Picornaviridae, transmits via fecal-oral route through person-to-person contact, contaminated food, or contaminated water. The virus demonstrates extraordinary environmental stability, surviving for months in water and on environmental surfaces. Following ingestion, the virus replicates in hepatocytes, is secreted into bile, and excreted in faeces at high concentrations beginning approximately one to two weeks before jaundice onset and continuing for one to two weeks after onset. The incubation period averages 28 to 30 days with range of 15 to 50 days. Clinical presentation varies by age: children under six years experience predominantly asymptomatic or mild non-specific illness, while older children and adults develop symptomatic disease characterised by acute onset of fever, malaise, anorexia, nausea, abdominal discomfort, dark urine, and jaundice. Alanine aminotransferase and aspartate aminotransferase rise to 10 to 100 times upper limit of normal. The illness typically lasts several weeks with full recovery in most cases. Fulminant hepatic failure develops rarely, affecting less than one percent of cases overall but up to two percent of adults over 40 years. Hepatitis A infection confers lifelong immunity; chronic infection does not occur. Hepatitis A vaccination provides highly effective protection and is incorporated into childhood immunisation schedules in many European countries, though coverage varies substantially across the EU/EEA.
Hepatitis E virus, a non-enveloped positive-sense single-stranded RNA virus of the family Hepeviridae, exists as multiple genotypes with distinct epidemiology. Genotypes 1 and 2 primarily affect Asia and Africa, transmitting through faecally contaminated water and causing large waterborne outbreaks. Genotype 3, endemic in Europe, transmits zoonotically through consumption of undercooked meat from infected pigs, wild boar, or deer. Genotype 4 predominates in Asia. The incubation period averages 40 days with range of 15 to 60 days. Clinical presentation resembles hepatitis A with acute onset of jaundice, dark urine, abdominal pain, anorexia, nausea, and elevated aminotransferases. Most immunocompetent individuals recover fully within weeks. However, hepatitis E demonstrates substantially higher mortality in pregnant women, particularly during the third trimester, with case fatality rates reaching 20 to 25% in some settings. Chronic hepatitis E develops in immunocompromised individuals—particularly solid organ transplant recipients and patients with haematological malignancies—progressing to cirrhosis if untreated. Ribavirin demonstrates efficacy for chronic hepatitis E. No hepatitis E vaccine is licensed in Europe, though a vaccine is available in China.
The urgent public health priorities for Bulgaria’s acute viral hepatitis surge include: immediate virological characterisation of recent cases to determine whether hepatitis A, hepatitis E, or multiple agents are contributing; detailed epidemiological investigation including case interviews to identify common food exposures, restaurant patronage, drinking water sources, and other risk factors; food and environmental sampling if epidemiological investigation suggests foodborne or waterborne sources; review of hepatitis A vaccination coverage and consideration of emergency vaccination campaigns targeting at-risk populations if hepatitis A is confirmed as predominant agent; enhanced surveillance and provider education to ensure prompt case detection and reporting; and public health messaging regarding hepatitis A vaccination, hand hygiene, food safety practices, and proper cooking of pork and game meats. The 198% year-over-year increase cannot be explained by routine surveillance enhancement or incidental variation and demands comprehensive investigation and control measures.
Contact and Sexual Transmission
Lyme borreliosis surveillance documented seven laboratory-confirmed cases during Week 5, representing a 75% increase from the four cases reported during Week 4 and the highest weekly count since January began. Cases were reported from Lovech (one case), Montana (one case), Pleven (three cases), Ruse (one case), and Shumen (one case). Since the beginning of 2026, Bulgaria recorded 19 cumulative Lyme borreliosis cases compared to 13 cases during the equivalent period in 2025, representing a 46% year-over-year increase. However, interpretation of early-year Lyme borreliosis notifications requires caution because Lyme disease demonstrates strong seasonality with peak transmission during late spring through early autumn when tick activity and human outdoor recreational activity coincide. January cases likely represent either late manifestations of infections acquired during the previous tick season, diagnostic delays leading to notification lag, or potentially tick exposures during unusually warm winter weather if microclimatic conditions and vegetation permitted tick activity.
Lyme borreliosis, caused by spirochetes of the Borrelia burgdorferi sensu lato complex—primarily Borrelia burgdorferi sensu stricto, Borrelia afzelii, and Borrelia garinii in Europe—transmits through bites of infected Ixodes ticks. Ixodes ricinus serves as the primary vector in most of Europe. The ticks acquire infection by feeding on infected reservoir hosts including small mammals, particularly rodents, and birds. Tick activity peaks during spring through autumn when temperatures and humidity support off-host survival and host-seeking behaviour. Following tick attachment and blood feeding, spirochete transmission requires approximately 24 to 48 hours, providing opportunity for infection prevention through prompt tick removal.
Lyme borreliosis manifests in stages. Early localised infection presents with erythema migrans—an expanding annular erythematous lesion with central clearing appearing days to weeks after tick bite—accompanied by fever, headache, myalgia, and regional lymphadenopathy in some cases. Early disseminated infection develops weeks to months after initial infection if untreated, manifesting as multiple erythema migrans lesions, neurological complications including facial nerve palsy and lymphocytic meningitis, cardiac complications including atrioventricular block, and arthralgias. Late disseminated infection develops months to years after initial infection, manifesting as intermittent or chronic arthritis affecting large joints, particularly knees, and neurological complications including encephalopathy and polyneuropathy. Borrelia afzelii particularly associates with dermatological manifestations including acrodermatitis chronica atrophicans, while Borrelia garinii particularly associates with neurological manifestations. Antibiotic treatment with doxycycline, amoxicillin, or ceftriaxone—depending on disease stage and manifestations—achieves cure in most cases.
Lyme borreliosis prevention focuses on avoiding tick exposure through protective clothing during outdoor activities in tick-endemic areas, using insect repellents containing DEET or picaridin on exposed skin and permethrin on clothing, performing tick checks after outdoor activities, and promptly removing attached ticks. Education of populations engaging in outdoor recreational activities in forested and grassy areas endemic for Lyme borreliosis represents an important public health intervention. The increase in early-2026 notifications may reflect improved diagnostic awareness and testing, though the 46% year-over-year increase warrants continued monitoring through the approaching tick season to assess whether this represents secular trend toward higher Lyme borreliosis incidence requiring enhanced prevention messaging and surveillance.
Syphilis surveillance documented 11 laboratory-confirmed cases during Week 5, representing a 450% increase from the two cases reported during Week 4 and the highest weekly count recorded in 2026. Cases were reported from Plovdiv (13 cases—likely representing multiple region numbers aggregated), Varna (one case), and Silistra (one case—though totals suggest data interpretation complexity). Since the beginning of 2026, Bulgaria recorded 31 cumulative syphilis cases compared to 32 cases during the equivalent period in 2025, representing minimal year-over-year change. The substantial week-to-week volatility—ranging from two cases in Week 4 to 11 cases in Week 5—reflects the stochastic variation typical of relatively uncommon reportable diseases and potential batch reporting of diagnosed cases from specific laboratories or clinics rather than actual weekly incidence patterns.
Syphilis, caused by Treponema pallidum subspecies pallidum, transmits through sexual contact with infectious lesions during primary or secondary syphilis, through vertical transmission from infected mother to foetus, or rarely through blood transfusion or needle sharing. The spirochete penetrates intact mucous membranes or abraded skin, disseminates through blood and lymphatics, and persists in multiple tissues if untreated. The incubation period averages 21 days with range of 10 to 90 days. Primary syphilis manifests as a painless ulcer (chancre) at the inoculation site—genitals, anus, mouth, or other sites—accompanied by regional lymphadenopathy. The chancre resolves spontaneously within three to six weeks even without treatment. Secondary syphilis develops weeks to months after primary infection in untreated individuals, manifesting as disseminated disease with non-pruritic maculopapular rash classically involving palms and soles, mucocutaneous lesions, generalised lymphadenopathy, and constitutional symptoms. Latent syphilis follows secondary stage, divided into early latent (within one year of infection) and late latent (more than one year after infection). Tertiary syphilis develops years to decades after initial infection in approximately one-third of untreated individuals, manifesting as cardiovascular complications including aortitis and aortic aneurysms, gummatous lesions affecting skin, bones, and viscera, and neurosyphilis. Congenital syphilis results from vertical transmission, causing foetal death, premature birth, low birthweight, and multi-system manifestations in surviving infants including skeletal abnormalities, hepatosplenomegaly, and neurological sequelae.
Syphilis diagnosis employs serological testing with non-treponemal tests (rapid plasma reagin or Venereal Disease Research Laboratory) and treponemal-specific tests (enzyme immunoassays, chemiluminescence immunoassays, or Treponema pallidum particle agglutination). Direct detection via darkfield microscopy or nucleic acid amplification is possible from primary lesions but rarely performed. Penicillin remains the treatment of choice for all stages of syphilis, with regimen and duration varying by disease stage. Doxycycline or ceftriaxone serve as alternatives for penicillin-allergic patients, though penicillin desensitisation is recommended for pregnant women requiring treatment.
Syphilis incidence has increased in many European countries over the past two decades, particularly affecting men who have sex with men, though heterosexual transmission also contributes. Congenital syphilis has increased in several European countries, reflecting inadequate antenatal screening coverage or treatment failures. Bulgaria’s stable year-over-year syphilis notifications at approximately 30 cases per five-week period, while representing relatively low absolute burden, warrant maintenance of comprehensive sexually transmitted infection control programmes including accessible testing, partner notification and treatment, congenital syphilis prevention through universal antenatal screening, and sexual health education.
Gonorrhoea surveillance documented four laboratory-confirmed cases during Week 5, doubling the two cases reported during Week 4. Since the beginning of 2026, Bulgaria recorded 16 cumulative gonorrhoea cases compared to six cases during the equivalent period in 2025, representing a 167% year-over-year increase. While the absolute number of cases remains small, the substantial percentage increase warrants attention to assess whether this represents enhanced surveillance and testing capacity, changes in population behaviour or healthcare-seeking, or true increase in gonococcal transmission.
Neisseria gonorrhoeae, a Gram-negative diplococcus, transmits through sexual contact with infected mucous membranes. The bacterium infects columnar epithelium of the urethra, endocervix, rectum, pharynx, and conjunctiva. The incubation period ranges from one to 14 days, typically two to five days. In men, urethral infection manifests as acute urethritis with purulent discharge and dysuria; asymptomatic infection occurs in approximately ten percent. In women, endocervical infection causes mucopurulent cervicitis, though 50% or more of infections are asymptomatic; complications include ascending infection causing pelvic inflammatory disease, ectopic pregnancy, and infertility. Rectal and pharyngeal infections are frequently asymptomatic. Disseminated gonococcal infection develops rarely, manifesting as arthritis-dermatitis syndrome or isolated septic arthritis. Ophthalmia neonatorum results from vertical transmission during delivery, causing purulent conjunctivitis with risk of corneal perforation and blindness if untreated.
Neisseria gonorrhoeae has progressively developed resistance to multiple antibiotic classes including sulphonamides, penicillins, tetracyclines, fluoroquinolones, and most recently extended-spectrum cephalosporins. Current European treatment guidelines recommend dual therapy with ceftriaxone and azithromycin to maximise cure rates and reduce selection for resistance. However, ceftriaxone-resistant strains have been detected across Europe, raising concerns about emergence of untreatable gonorrhoea. Enhanced gonococcal surveillance including antimicrobial susceptibility testing and monitoring of treatment failures is essential for maintaining treatment effectiveness.
Urogenital chlamydial infection surveillance documented six laboratory-confirmed cases during Week 5, a 50% increase from the four cases reported during Week 4. Since the beginning of 2026, Bulgaria recorded 23 cumulative urogenital chlamydial infection cases compared to 11 cases during the equivalent period in 2025, representing a 109% year-over-year increase. Similar to gonorrhoea, interpretation must consider whether this increase reflects enhanced testing capacity, particularly increased availability of nucleic acid amplification testing, changes in screening programmes, or true increase in transmission.
Chlamydia trachomatis serovars D through K cause urogenital chlamydial infection, the most frequently reported bacterial sexually transmitted infection in Europe. The obligate intracellular bacterium transmits through sexual contact, infecting columnar epithelium of the urethra, endocervix, rectum, and conjunctiva. The incubation period ranges from seven to 21 days. In men, urethral infection causes urethritis with mucoid or purulent discharge and dysuria, though approximately 50% of infections are asymptomatic. In women, endocervical infection causes mucopurulent cervicitis, though 70% or more of infections are asymptomatic; untreated infection may ascend to cause pelvic inflammatory disease, chronic pelvic pain, ectopic pregnancy, and tubal factor infertility. Rectal infections are frequently asymptomatic. Lymphogranuloma venereum, caused by Chlamydia trachomatis serovars L1, L2, and L3, causes invasive anorectal disease and has increased among men who have sex with men in Europe.
Diagnostic testing employs nucleic acid amplification testing on first-void urine in men or vaginal swabs, endocervical swabs, or urine in women, with substantially higher sensitivity than older culture or antigen detection methods. Treatment with azithromycin single dose or doxycycline seven-day course achieves cure in most cases. Test-of-cure is not routinely recommended unless symptoms persist, pregnancy, or concerns about adherence. Partner notification and treatment prevent reinfection and onward transmission.
The doubling of chlamydial infection cases year-over-year likely reflects multiple factors including increased testing through expanded screening programmes, greater availability of nucleic acid amplification testing with higher sensitivity detecting infections missed by previous diagnostic methods, increased healthcare-seeking for sexual health services, and potentially increased transmission. Distinguishing these contributions requires examination of testing volumes, positivity rates, and demographic characteristics of cases. Regardless of the primary driver, the increases in both chlamydial infection and gonorrhoea underscore the importance of comprehensive sexually transmitted infection control programmes including accessible testing and treatment services, partner notification, sexual health education, and promotion of condom use.
HIV surveillance documented five laboratory-confirmed new diagnoses during Week 5, a 28.6% decline from the seven cases reported during Week 4. Since the beginning of 2026, Bulgaria recorded 19 cumulative HIV diagnoses compared to 28 diagnoses during the equivalent period in 2025, representing a 32.1% year-over-year decline. Interpretation of early-year HIV diagnosis trends requires caution given small numbers and potential seasonal variation in testing volumes and diagnosis reporting. However, if this decline represents sustained trend, it would indicate progress in HIV prevention though continued vigilance and combination prevention programming remains essential.
HIV transmission in Bulgaria occurs primarily through sexual contact—both heterosexual and among men who have sex with men—and injection drug use, with mother-to-child transmission prevented through universal antenatal screening and antiretroviral prophylaxis. Bulgaria’s HIV epidemic remains concentrated among key populations at higher risk including men who have sex with men, people who inject drugs, and sex workers. Early diagnosis and initiation of antiretroviral therapy improves individual health outcomes and eliminates transmission risk through viral suppression, supporting the UNAIDS 95-95-95 targets: 95% of people living with HIV knowing their status, 95% of diagnosed individuals receiving antiretroviral therapy, and 95% of those on treatment achieving viral suppression.
Congenital syphilis surveillance documented zero cases during Week 5. Since the beginning of 2026, Bulgaria recorded two cumulative congenital syphilis cases compared to three cases during the equivalent period in 2025. While the absolute numbers are small, any congenital syphilis case represents a sentinel event indicating missed opportunities for prevention through inadequate antenatal screening coverage, delayed antenatal care initiation, lack of partner treatment, or treatment failure. Universal antenatal syphilis screening in early pregnancy with prompt treatment of seropositive pregnant women prevents virtually all congenital syphilis cases. The occurrence of two congenital syphilis cases during the first five weeks of 2026 warrants review of antenatal screening protocols, coverage achieved, treatment provision for positive cases, and partner notification and treatment to identify system gaps requiring intervention.