Epidemiological News: Week 44, 2025
Overview
Week 44 of 2025, spanning October 27 through November 2, presents a comprehensive view of the global epidemiological landscape with particular focus on infectious disease surveillance across multiple continents and regulatory developments in pharmaceutical therapeutics. This report synthesizes surveillance data from international, European, and national health authorities, including the World Health Organization, the European Centre for Disease Prevention and Control, the European Food Safety Authority, the European Medicines Agency, and the Bulgarian National Centre of Infectious and Parasitic Diseases. The persistence of vector-borne diseases into early November, coupled with ongoing surveillance of respiratory pathogens and sexually transmitted infections, underscores the dynamic nature of infectious disease epidemiology in an era of climate change, global mobility, and evolving pathogen behavior.
Pharmaceutical Advances and Regulatory Actions
The European Medicines Agency concluded its October 2025 meeting with several significant regulatory decisions that will impact clinical practice across Europe and potentially influence global therapeutic approaches to chronic diseases. The Committee for Medicinal Products for Human Use recommended approval for two novel therapeutic agents addressing previously inadequately treated conditions, while declining authorization for one product under consideration for chronic graft-versus-host disease.
Brinsupri, containing the active substance brensocatib, received a positive opinion as the first authorized treatment specifically for non-cystic fibrosis bronchiectasis. This chronic pulmonary condition affects thousands of patients across Europe and is characterized by permanent dilation and damage to the bronchial airways, resulting from recurrent infections, inflammation, and impaired mucociliary clearance. Patients with bronchiectasis experience chronic productive cough, recurrent pulmonary infections, progressive decline in lung function, and significantly impaired quality of life. The disease typically follows a progressive course with alternating periods of clinical stability and acute exacerbations requiring antimicrobial therapy and sometimes hospitalization. Brensocatib represents a mechanism-based approach targeting neutrophil serine proteases, which play a central role in the inflammatory cascade driving bronchiectasis progression. The availability of this treatment addresses a significant unmet medical need, as previous management strategies relied primarily on symptomatic treatment with bronchodilators, mucolytics, and antibiotics without disease-modifying therapies.
Wayrilz, with the active substance rilzabrutinib, received positive recommendation for treatment of immune thrombocytopenia in adult patients who have proven refractory to other therapeutic interventions. Immune thrombocytopenia is an autoimmune disorder characterized by accelerated platelet destruction and inadequate platelet production, resulting in thrombocytopenia that places patients at risk for spontaneous bleeding, including potentially life-threatening intracranial hemorrhage. The condition significantly impacts patients’ daily activities, as those with severe thrombocytopenia must restrict physical activity to avoid trauma and may experience fatigue, petechiae, purpura, and mucosal bleeding. Rilzabrutinib functions as a Bruton tyrosine kinase inhibitor, targeting B-cell and macrophage function involved in antiplatelet antibody production and platelet destruction. For patients who have failed conventional therapies including corticosteroids, intravenous immunoglobulin, thrombopoietin receptor agonists, and splenectomy, this novel mechanism provides an important therapeutic alternative.
The Committee declined to recommend authorization for Rezurock, containing belumosudil, for treatment of chronic graft-versus-host disease. This decision reflects the rigorous evaluation process employed by European regulatory authorities to ensure that benefits clearly outweigh risks before medications receive marketing authorization. Chronic graft-versus-host disease remains a significant cause of morbidity and mortality following allogeneic hematopoietic stem cell transplantation, and the decision underscores the continuing need for effective therapies for this condition.
Beyond these specific approvals, the EMA Committee issued positive opinions for extensions of therapeutic indications for eight existing medicines, expanding the clinical scenarios in which these established treatments may be employed. These indication extensions typically reflect accumulated clinical experience, completed clinical trials demonstrating efficacy in new patient populations, or recognition of therapeutic utility in related conditions.
West Nile Virus: Continental Perspective and Transmission Dynamics
As of October 3, 2025, the European surveillance network has recorded 989 confirmed WNV cases across 13 member countries, marking a significant year for West Nile virus activity in the region. Italy leads with 714 cases and 48 fatalities, representing the most substantial outbreak in Europe. The primary affected regions include Lazio and Campania, where ecological conditions favor sustained mosquito breeding and bird populations that maintain the viral reservoir. The case fatality rate highlights the severity of infections in vulnerable populations, particularly elderly individuals and those with underlying immunosuppressive conditions. Greece, Serbia, and other Balkan nations continue to report active transmission, with the temporal pattern showing that cases began on June 2, 2025, peaked around late September, and continue under active monitoring into November.
The geographic distribution demonstrates the persistent establishment of WNV transmission cycles across Southern and Southeastern Europe, with mosquito vectors maintaining activity later into the season than historical averages. This extended transmission season likely reflects warmer autumn temperatures that prolong mosquito survival and activity, along with changes in precipitation patterns that create more persistent breeding sites. West Nile virus is primarily transmitted through the bite of infected Culex mosquitoes, particularly Culex pipiens in Europe. These mosquitoes typically feed during evening and nighttime hours, with peak biting activity occurring at dusk and dawn. The virus cannot be transmitted person-to-person through casual contact, though rare cases of transmission through blood transfusion, organ transplantation, and from mother to fetus during pregnancy have been documented.
The majority of WNV infections, approximately 80 percent, remain asymptomatic. About 20 percent of infected individuals develop West Nile fever, characterized by sudden onset of fever, headache, body aches, joint pain, and sometimes rash. Less than 1 percent of infections progress to severe neuroinvasive disease, including encephalitis, meningitis, or acute flaccid paralysis. The risk of severe disease increases dramatically with age, particularly in individuals over 60 years, and in those with compromised immune systems due to chronic disease, immunosuppressive medications, or organ transplantation.
Chikungunya Virus: Epidemiology and Emerging European Transmission
Autochthonous chikungunya transmission represents a growing public health concern in Southern Europe, marking a significant shift in the epidemiology of this arboviral disease. France has reported 768 total cases with 13 new cases documented in week 44, showing clustered transmission patterns that indicate localized outbreaks with ongoing risk for continued transmission. Italy has accumulated 370 total cases with one new case in the most recent reporting period, with geographic clustering suggesting focused transmission zones where enhanced entomological surveillance remains active.
The sustained transmission of chikungunya, a disease traditionally associated with tropical and subtropical regions of Africa, Asia, and the Indian Ocean islands, signals the expanding range of competent vectors and the adaptation of arboviral transmission to European climates. The primary vector responsible for European transmission is Aedes albopictus, commonly known as the Asian tiger mosquito. This highly adaptable mosquito species has successfully colonized much of Southern Europe over the past two decades, taking advantage of international trade and travel to establish populations far from its native Southeast Asian range. Unlike Culex mosquitoes that transmit West Nile virus, Aedes albopictus is a daytime feeder, with peak biting activity occurring during early morning and late afternoon hours.
Chikungunya virus is transmitted directly from human to mosquito to human, without requiring a bird or animal reservoir. When a mosquito bites an infected person during the viremic phase of illness, typically during the first week of symptoms, it can acquire the virus and subsequently transmit it to other people. This direct human-to-human transmission cycle through mosquito vectors allows for rapid amplification of cases in areas with high densities of competent mosquitoes and susceptible human populations. The disease presents with sudden onset of high fever and severe joint pain, often so debilitating that patients have difficulty walking. The name “chikungunya” derives from a Kimakonde word meaning “to become contorted,” referring to the stooped posture of patients suffering from severe arthralgia. While rarely fatal, the joint pain can persist for months or even years in some patients, causing significant morbidity and reduced quality of life.
The establishment of autochthonous transmission in France and Italy represents a sentinel event in European infectious disease epidemiology. Previously, chikungunya cases in Europe were exclusively travel-associated, with patients having acquired infection during visits to endemic areas. The documentation of local transmission indicates that all three necessary components for sustained arboviral disease have aligned: competent vector populations, suitable climatic conditions for viral replication and transmission, and sufficient numbers of susceptible hosts. This epidemiological transition has important implications for public health preparedness and vector control strategies across the continent.
Other Infectious Disease Activity in Europe
Mpox surveillance continues across Balkan countries, with Serbia reporting 40 confirmed cases, leading regional totals. Sporadic cases in neighboring countries demonstrate ongoing transmission, though at lower levels than observed during the peak of the 2022-2023 international outbreak. Mpox, formerly known as monkeypox, is caused by the monkeypox virus, an orthopoxvirus related to the virus that causes smallpox. Unlike the arboviral diseases discussed above, mpox transmits through close contact with infected individuals, including direct contact with skin lesions, respiratory droplets during prolonged face-to-face contact, and potentially through contaminated materials such as bedding or clothing.
The current outbreak in Europe is predominantly caused by clade IIb of the virus and is primarily affecting networks of men who have sex with men, though transmission can occur in any setting involving close physical contact. The disease typically presents with fever, headache, muscle aches, and exhaustion, followed by the development of a characteristic rash that progresses through stages from macules to papules, vesicles, pustules, and finally scabs. Enhanced contact tracing and isolation protocols remain critical for containing transmission chains, along with targeted vaccination campaigns using modified vaccinia Ankara vaccines for high-risk populations and post-exposure prophylaxis.
Respiratory virus activity continues under routine seasonal monitoring, with early indicators of the autumn and winter respiratory season beginning to emerge. Surveillance systems remain prepared for potential co-circulation of influenza, respiratory syncytial virus, and SARS-CoV-2, which could place strain on healthcare systems if multiple respiratory pathogens circulate simultaneously at high levels. The integration of molecular diagnostics and syndromic surveillance provides early warning of shifts in respiratory disease epidemiology.
Bulgaria: National Surveillance and Disease Trends
Vector-Borne Diseases in Bulgaria
Bulgaria’s position within the endemic Balkan region places it at ongoing risk for vector-borne diseases, particularly West Nile virus. During 2025, the country has documented one confirmed case of West Nile fever, representing a dramatic decline from the 28 cases reported during the same period in 2024. This substantial year-over-year reduction of 27 cases may reflect several factors, including variations in mosquito population density influenced by climatic conditions, changes in migratory bird patterns affecting viral introduction and amplification, or potentially more effective vector control measures implemented following previous seasons of high transmission.
The presence of WNV in Bulgaria reflects the country’s geographical position within the endemic zone that extends across the Balkans and Mediterranean basin. The Danube River basin and wetland areas provide suitable habitats for Culex mosquito species, which serve as the primary vectors for WNV transmission. These mosquitoes acquire the virus by feeding on infected migratory birds, which serve as the natural reservoir hosts. The virus then amplifies in the mosquito population and can be transmitted to humans and horses through subsequent mosquito bites. The enzootic cycle between birds and mosquitoes continues throughout the warm season, with human infections representing incidental spillover events rather than contributing to ongoing transmission.
During week 44 specifically, no new West Nile virus cases were detected, consistent with the expected seasonal decline in transmission as temperatures decrease and mosquito populations dwindle. However, the single case documented earlier in the year serves as a reminder that surveillance infrastructure must remain vigilant for this potentially severe neuroinvasive disease.
Tick-borne diseases continue to circulate in Bulgaria, with Lyme borreliosis representing the most frequently reported tick-borne infection. Week 44 saw seven confirmed cases of Lyme borreliosis, bringing the year-to-date total to 358 cases, compared with 349 cases during the same period in 2024. This modest increase of nine cases suggests stable endemic transmission of Borrelia burgdorferi sensu lato through Ixodes tick vectors. Lyme disease typically manifests initially with the characteristic erythema migrans rash at the site of tick attachment, followed potentially by disseminated infection involving the nervous system, heart, or joints if left untreated. The autumn season traditionally sees declining Lyme disease incidence as tick activity diminishes with cooler weather, though cases diagnosed in autumn often represent infections acquired during peak summer tick activity with delayed clinical presentation.
Mediterranean spotted fever, known locally as Marseilles fever, continues to be documented in Bulgaria, with one confirmed case reported during week 44, bringing the annual total to 76 cases. This represents a slight decrease from the 81 cases documented in 2024. Mediterranean spotted fever is caused by Rickettsia conorii transmitted by the brown dog tick Rhipicephalus sanguineus. The disease presents with fever, headache, and a characteristic papular rash, along with the pathognomonic tache noire, a dark eschar at the site of tick attachment. The continuing documentation of cases underscores the endemic nature of this rickettsial disease in the Balkan region.
Gastrointestinal and Foodborne Infections
Gastrointestinal infections represent a significant proportion of Bulgaria’s infectious disease burden, with multiple pathogens contributing to the overall epidemiological picture. During week 44, the country reported 178 cases of gastroenteritis and enterocolitis of various etiologies, including 87 possible cases, 84 probable cases, and seven confirmed cases. The year-to-date total of 8,194 cases represents a decrease of 479 cases compared with the 8,673 cases documented during the equivalent period in 2024, suggesting a modest downward trend in overall gastrointestinal disease burden.
Salmonellosis continues to circulate at endemic levels, with 15 confirmed cases reported during week 44. The cumulative annual total of 612 cases represents a substantial decrease from the 856 cases documented in 2024, with the reduction of 244 cases potentially reflecting improved food safety measures, changes in agricultural practices affecting animal reservoirs, or shifts in dietary patterns affecting exposure to contaminated foods. Salmonellosis typically results from consumption of contaminated poultry products, eggs, or produce, with symptoms including diarrhea, fever, and abdominal cramping developing 12 to 72 hours after exposure.
Campylobacteriosis demonstrated increased activity during week 44, with 14 cases reported, bringing the annual total to 398 cases. This represents a notable increase of 119 cases compared with the 279 cases documented in 2024, potentially reflecting enhanced laboratory detection capabilities, changes in food production or handling practices, or true increases in infection incidence. Campylobacter species, particularly Campylobacter jejuni, represent the most common bacterial cause of gastroenteritis worldwide and are typically acquired through consumption of undercooked poultry, unpasteurized milk, or contaminated water.
Rotavirus gastroenteritis continues to affect primarily pediatric populations, with 11 confirmed cases reported during week 44. The year-to-date total of 641 cases remains relatively stable compared with the 648 cases in 2024. Rotavirus remains a leading cause of severe dehydrating diarrhea in young children despite the availability of effective vaccines, with transmission occurring through the fecal-oral route in settings where young children congregate.
Five confirmed cases of E. coli enteritis were documented during week 44, contributing to an annual total of 275 cases. This represents a decline from the 309 cases reported in 2024. While no cases of Shiga toxin-producing E. coli were reported, the ongoing surveillance for these potentially severe infections remains important given their capacity to cause hemolytic uremic syndrome, particularly in young children.
Respiratory and Invasive Bacterial Infections
COVID-19 surveillance continues in Bulgaria, with 228 confirmed cases reported during week 44, representing a decline of 30 cases from the previous week. The year-to-date total of 2,491 cases reflects a dramatic reduction from the 14,341 cases documented during the same period in 2024, with the decrease of 11,850 cases consistent with global trends showing declining COVID-19 incidence as population immunity from vaccination and previous infection accumulates. However, the continuing documentation of several hundred cases weekly underscores that SARS-CoV-2 remains in circulation and continues to cause symptomatic disease requiring medical attention.
Varicella, commonly known as chickenpox, demonstrated substantial activity during week 44, with 312 cases reported. The annual total of 17,781 cases represents a decrease of 4,600 cases from the 22,381 cases in 2024. Varicella remains a highly contagious disease primarily affecting children, transmitted through respiratory droplets and direct contact with vesicular lesions. The disease typically presents with a characteristic pruritic vesicular rash along with fever and malaise. While usually self-limited in healthy children, varicella can cause serious complications in immunocompromised individuals, pregnant women, and occasionally in healthy adults.
Scarlet fever activity continued during week 44, with 53 cases reported, including 17 possible, 26 probable, and 10 confirmed cases. The year-to-date total of 2,926 cases represents a substantial decrease from the 7,640 cases documented in 2024. Scarlet fever is caused by group A streptococcus producing erythrogenic toxins and presents with fever, pharyngitis, and a characteristic sandpaper-like rash. The decline may reflect natural cyclical variations in streptococcal disease activity or changes in diagnostic practices.
Invasive bacterial meningitis cases remain under close surveillance, with three cases of bacterial meningitis due to other or unspecified organisms reported during week 44. No cases of pneumococcal, streptococcal, or Haemophilus influenzae meningitis were documented during the reporting week. The annual total of 13 meningococcal infections represents an increase from six cases in 2024, warranting continued vigilance for this potentially rapidly fatal infection.
One case of Legionnaires’ disease was confirmed during week 44, bringing the annual total to 11 cases, compared with 10 cases in 2024. Legionnaires’ disease results from inhalation of water aerosols contaminated with Legionella pneumophila and presents as severe pneumonia that can be fatal without appropriate antibiotic therapy. Sporadic cases typically reflect environmental exposure in buildings with contaminated water systems.
Sexually Transmitted Infections
Sexually transmitted infections continue to represent an important public health concern in Bulgaria, with ongoing transmission of multiple pathogens documented through surveillance systems. Week 44 saw 10 confirmed HIV infections, bringing the year-to-date total to 259 cases, representing an increase of 21 cases compared with the 238 cases in 2024. This upward trend in HIV diagnoses may reflect increased transmission, improved case detection through expanded testing initiatives, or delayed diagnoses of infections acquired in previous years.
Syphilis surveillance documented six confirmed cases during week 44, contributing to an annual total of 304 cases, compared with 282 cases in 2024. Particularly concerning is the documentation of 33 cases of congenital syphilis during 2025, a dramatic increase from the 12 cases in 2024. Congenital syphilis results from maternal-fetal transmission during pregnancy and can cause severe fetal and neonatal complications including stillbirth, neonatal death, and serious long-term sequelae in survivors. The substantial increase in congenital syphilis cases suggests gaps in prenatal screening and treatment programs that require urgent public health attention.
Urogenital chlamydial infection showed seven confirmed cases during week 44, with the annual total of 161 cases representing a substantial increase from the 91 cases in 2024. Chlamydia trachomatis is the most commonly reported bacterial sexually transmitted infection and can cause cervicitis, urethritis, and pelvic inflammatory disease if left untreated, with potential complications including ectopic pregnancy and infertility.
Gonorrhea surveillance documented three confirmed cases during week 44, contributing to a year-to-date total of 103 cases, compared with 79 cases in 2024. The increasing trend in gonorrhea cases parallels global patterns and raises concerns about antimicrobial resistance in Neisseria gonorrhoeae, which has developed resistance to multiple classes of antibiotics historically used for treatment.
Rare and Emerging Infections
Several rare infections were documented in Bulgaria during 2025, though no new cases occurred during week 44. Single cases of botulism, Crimean-Congo hemorrhagic fever, and typhoid fever were reported during the year, along with four cases of hemorrhagic fever with renal syndrome, five dengue cases, and two mpox cases. The documentation of these relatively rare infections underscores the importance of comprehensive surveillance systems capable of detecting diverse pathogens and the global mobility of populations that can introduce infections from endemic areas.
Pertussis, which caused a substantial outbreak in 2024 with 2,668 cases, has shown dramatically reduced activity in 2025, with only 82 cases reported year-to-date. This represents a decrease of 2,586 cases and likely reflects the cyclical nature of pertussis epidemiology, with epidemic peaks occurring every three to five years followed by inter-epidemic periods of low transmission.
Public Health Implications and Disease Control Strategies
Understanding Vector-Borne Disease Trends
The epidemiological data from week 44 reinforces several critical observations about the changing landscape of vector-borne diseases in Europe. The persistence of WNV and chikungunya cases into November indicates warming trends and the establishment of competent vectors across broader European territories. Historical transmission seasons for these diseases typically concluded by mid-October, but the documentation of cases extending into November suggests that climate change is creating conditions favorable for prolonged vector activity. The involvement of 13 countries in WNV surveillance, coupled with autochthonous chikungunya transmission in previously unaffected regions, demonstrates the northward expansion of arboviral disease risk.
The 48 fatalities associated with West Nile virus in Italy underscore the severe outcomes possible in elderly and immunocompromised individuals, necessitating targeted prevention strategies for vulnerable populations. The neuroinvasive complications of WNV infection can result in long-term disability even among survivors, with some patients experiencing persistent neurological sequelae including memory problems, difficulty with concentration, and mood disorders. This burden of disease extends beyond the acute illness and requires consideration in public health planning and resource allocation.
Integrated Vector Management Approaches
Control of vector-borne diseases requires comprehensive integrated vector management strategies that combine multiple interventions to reduce disease transmission. For West Nile virus prevention, the primary focus centers on reducing Culex mosquito populations through environmental management and targeted larviciding. This includes eliminating standing water in artificial containers, treating catch basins and storm drains with larvicides, and managing vegetation around water bodies to reduce mosquito resting sites. Public health authorities conduct mosquito surveillance through trapping programs that monitor adult mosquito populations and test pools of mosquitoes for viral infection, providing early warning of viral activity before human cases occur.
Bird surveillance also plays a crucial role in WNV monitoring, as increased mortality among corvid species such as crows and blue jays often precedes human cases by several weeks. Dead bird surveillance programs allow public health officials to detect viral introduction into new areas and intensify control measures proactively. Equine surveillance provides another layer of early warning, as horses develop clinical disease with greater frequency than humans and are often infected before human cases emerge.
For chikungunya control, the focus shifts to managing Aedes albopictus populations, which requires different strategies than Culex control. Asian tiger mosquitoes breed in small artificial water-holding containers found in urban and suburban environments, including plant saucers, discarded tires, clogged gutters, and children’s toys. Control programs emphasize community engagement and source reduction, encouraging residents to eliminate potential breeding sites on their properties. This type of “backyard ecology” requires sustained public education campaigns and community mobilization to achieve meaningful reductions in mosquito populations. Adulticiding through ultra-low volume spraying can provide temporary relief during outbreaks but is not sustainable as a long-term control strategy due to the rapid recolonization ability of Aedes mosquitoes and concerns about insecticide resistance.
Personal protective measures remain essential for both WNV and chikungunya prevention. Public health messaging emphasizes the use of EPA-registered insect repellents containing DEET, picaridin, IR3535, or oil of lemon eucalyptus on exposed skin. Wearing long sleeves and long pants, particularly during peak mosquito activity times, provides mechanical protection against bites. Installing or repairing window and door screens prevents mosquitoes from entering indoor living spaces, and the use of air conditioning when available reduces human exposure by allowing people to remain indoors during peak transmission periods.
Surveillance and Response Systems
Active surveillance systems across Europe continue to provide critical early warning capabilities that enable rapid public health response. Real-time case reporting through integrated surveillance platforms allows health authorities to detect clusters and outbreaks quickly, enabling targeted interventions before widespread transmission occurs. Entomological surveillance guides vector control interventions by identifying areas of high vector density and viral activity, allowing resources to be deployed efficiently to areas of greatest risk. Cross-border collaboration through ECDC and other European networks facilitates coordinated public health action, ensuring that disease trends are recognized and addressed at the regional level rather than solely within individual countries.
Risk communication strategies adapted to local transmission intensity help maintain public awareness without generating unnecessary alarm. During periods of high transmission, public health authorities issue advisories encouraging enhanced personal protective measures and may recommend cancellation of outdoor evening activities in high-risk areas. Laboratory-based surveillance through sentinel physician networks and hospital-based reporting provides denominator data that allows calculation of disease incidence rates and monitoring of temporal trends. The integration of human, animal, and vector surveillance exemplifies the One Health approach to disease prevention, recognizing that human health is inextricably linked to animal health and environmental factors.
Recommendations for Health Professionals
Healthcare providers should maintain a high index of suspicion for arboviral infections in febrile patients with appropriate exposure history, particularly during the transmission season. West Nile virus should be considered in the differential diagnosis for patients presenting with unexplained encephalitis or meningoencephalitis, especially in individuals over 50 years of age or with immunocompromising conditions. Diagnostic testing through serology, PCR, or viral culture should be pursued promptly, and suspected cases should be reported to national surveillance systems according to local protocols. Clinical management remains primarily supportive, as no specific antiviral therapy exists for West Nile virus or chikungunya infections.
For chikungunya, the characteristic severe arthralgia provides an important diagnostic clue, particularly when fever and joint pain develop suddenly in patients without recent travel to traditionally endemic areas. Clinicians should recognize that autochthonous transmission now occurs in Europe and maintain awareness of local transmission patterns. Management focuses on symptomatic relief with analgesics and anti-inflammatory medications, with some patients requiring short-term use of corticosteroids for persistent arthritis.
Vector control professionals should continue eliminating mosquito breeding sites in urban and peri-urban environments through source reduction campaigns and consider larvicidal treatments in high-risk areas where breeding site elimination is not feasible. Resistance monitoring should guide insecticide selection to ensure continued efficacy of control programs. Public education campaigns should continue emphasizing personal protective measures and community participation in source reduction efforts.
Public health officials should anticipate potential persistence of transmission due to climate factors and prepare for the 2026 transmission season by incorporating lessons learned from current surveillance data. This includes enhancing laboratory capacity for arboviral diagnostics, training healthcare providers in recognition and management of arboviral diseases, and developing risk communication materials appropriate for diverse populations. Vaccine development efforts for West Nile virus and chikungunya should be supported, as immunization represents the most sustainable long-term approach to disease prevention.
Conclusion
Week 44 of 2025 demonstrates that infectious disease surveillance and public health preparedness remain critical across multiple geographic scales, from global pharmaceutical development to national disease monitoring systems. The 989 West Nile virus cases across Europe, hundreds of chikungunya infections establishing autochthonous transmission in previously unaffected areas, and Bulgaria’s diverse infectious disease portfolio spanning vector-borne diseases, gastrointestinal infections, sexually transmitted infections, and respiratory pathogens collectively illustrate the complex epidemiological landscape of contemporary Europe.
The regulatory approval of novel therapeutics for non-cystic fibrosis bronchiectasis and refractory immune thrombocytopenia by the European Medicines Agency represents significant advances in addressing conditions with substantial unmet medical needs. These pharmaceutical developments complement infectious disease control efforts by expanding the therapeutic armamentarium available to clinicians managing chronic diseases that may increase susceptibility to infections or complicate their management.
Bulgaria’s comprehensive surveillance data for week 44 and the year-to-date period reveal several epidemiological trends warranting attention. The dramatic increase in congenital syphilis cases from 12 in 2024 to 33 in 2025 represents a public health emergency requiring immediate enhancement of prenatal screening and treatment programs. The substantial increase in viral hepatitis cases, from 580 to 1,236 annually, necessitates detailed investigation to characterize the etiologic agents involved and identify transmission chains amenable to intervention. Conversely, the dramatic decline in pertussis from 2,668 cases in 2024 to 82 in 2025 demonstrates the cyclical nature of some infectious diseases and the importance of maintaining high vaccination coverage to prevent resurgence.
The persistence of arboviral transmission into November across Europe, including Bulgaria’s participation in regional West Nile virus surveillance despite documenting only one case in 2025, signals fundamental shifts in the ecology of disease transmission. The country’s position within the endemic Balkan region places it at ongoing risk not only for West Nile virus but potentially for future introduction of chikungunya transmission should Aedes albopictus populations become established. The coordination between national surveillance systems, particularly the work of the Bulgarian National Centre of Infectious and Parasitic Diseases, and European agencies such as ECDC and EFSA provides the essential foundation for effective monitoring and response to emerging and re-emerging infectious disease threats.
The integration of human, veterinary, and entomological surveillance through One Health approaches has proven essential for early detection and response to zoonotic and vector-borne diseases. The ability to detect viral activity in mosquito and bird populations before human cases emerge allows public health authorities to implement preventive measures and issue timely warnings to vulnerable populations. The continued refinement of these integrated surveillance systems will be crucial as climate change continues to alter the geographic distribution and seasonal timing of vector-borne disease transmission, while global travel patterns facilitate rapid pathogen dispersal across continents.
As Europe transitions into the cooler months, sustained vigilance remains essential across all components of the infectious disease surveillance and response infrastructure. Public health authorities are incorporating lessons learned from the 2025 transmission season into preparations for 2026, recognizing that each year provides new insights into the changing ecology of these diseases. The ongoing documentation of autochthonous chikungunya transmission in France and Italy, the concerning trends in sexually transmitted infections in Bulgaria, and the regulatory advances in chronic disease management collectively underscore that public health in the 21st century requires comprehensive, coordinated, and adaptive approaches that span infectious and non-communicable diseases, national and international boundaries, and human and animal health sectors.
Data Sources
The epidemiological data and regulatory information presented in this report are synthesized from multiple authoritative sources across international, European, and national surveillance networks. Primary infectious disease surveillance data are derived from the European Centre for Disease Prevention and Control weekly surveillance reports, which aggregate case reports from national public health institutes across member states according to standardized European case definitions. The European Food Safety Authority contributes specialized vector-borne disease monitoring data, with particular emphasis on the intersection of animal health, environmental factors, and human disease risk through integrated One Health surveillance frameworks.
Bulgarian national surveillance data are provided by the National Centre of Infectious and Parasitic Diseases, accessible at ncipd.org, which operates the country’s comprehensive communicable disease surveillance system. The NCIPD collects, analyzes, and disseminates epidemiological information on all notifiable infectious diseases in Bulgaria, providing weekly operational analyses that inform public health decision-making at national and regional levels. All Bulgarian case data represent confirmed, probable, or possible cases according to national case definitions that align with European Union standards for cross-border disease surveillance and reporting.
Pharmaceutical regulatory information derives from the European Medicines Agency Committee for Medicinal Products for Human Use meeting outcomes, available at ema.europa.eu, which provides authoritative information on medicinal product approvals, indication extensions, and regulatory decisions affecting therapeutic options across the European Economic Area.
For detailed case definitions, specific outbreak investigations, regional risk assessments, and clinical management guidance, healthcare providers and public health professionals should consult the ECDC website at ecdc.europa.eu, the EFSA website at efsa.europa.eu, the EMA website at ema.europa.eu, and the Bulgarian NCIPD website at ncipd.org, where regularly updated technical documents, surveillance reports, and guidance materials are publicly available. National health authorities in individual countries may provide additional country-specific guidance, reporting requirements, and clinical protocols that supplement European-level recommendations.
Note: This report summarizes publicly available surveillance data for educational and public health purposes. Healthcare providers should consult official national and regional guidelines for clinical management and reporting requirements.