Non-Communicable Disease and Healthcare System Developments
EMA Pharmacovigilance Risk Assessment Committee: May 2026 Meeting
The EMA Pharmacovigilance Risk Assessment Committee (PRAC) convened from 4 to 7 May 2026, with a substantively dense agenda encompassing new safety signals, extensions of indication, post-authorisation safety study submissions, and marketing authorisation renewals.
Seven new safety signals were identified for regulatory assessment. The most significant from a public health standpoint is a class-wide signal for benzodiazepines: across 48 products—including alprazolam, diazepam, lorazepam, clonazepam, midazolam, and numerous fixed-dose combinations—a signal of miscarriage associated with in utero exposure has been identified, with 17 European member states designated as leads and the evaluation proceeding under EPITT 20272. Given the frequency of benzodiazepine prescribing in reproductive-age women for anxiety, insomnia, and epilepsy management, this signal has immediate clinical implications and warrants communication to prescribers and patients before any formal regulatory conclusion is reached. A second signal, of encephalopathy associated with amoxicillin and amoxicillin-clavulanic acid, has been identified (EPITT 20264, leads Austria and Germany); this neurotoxic complication, while uncommon, has been sporadically reported in the literature particularly in patients with renal impairment, and its formal evaluation reinforces the need for prescriber vigilance in this population.
Two distinct signals for GLP-1 receptor agonists and related agents merit attention given the rapid and widespread expansion of this drug class in clinical practice. First, a signal of peripheral neuropathies has been identified for exenatide (Bydureon, Byetta) and the semaglutide family (Ozempic, Rybelsus, Wegovy, Kayshild), along with the insulin icodec/semaglutide combination Kyinsu (EPITT 20270, lead Sweden). Second, a separate signal of gastrointestinal volvulus has been identified specifically for semaglutide products (EPITT 20260, lead Sweden). Gastrointestinal dysmotility has become an increasingly recognised adverse effect profile associated with GLP-1 receptor agonists, and this signal—if confirmed—would represent a serious, potentially life-threatening complication. Additional new signals this cycle include lichen sclerosus associated with dapagliflozin (EPITT 20259, lead Sweden), Behçet’s syndrome associated with ixekizumab (Taltz; EPITT 20269, lead Germany), and cutaneous vasculitis associated with tocilizumab products (EPITT 20261, lead Germany).
Among the procedural extensions of clinical note, tirzepatide (Mounjaro) is under assessment for an extension of indication to reduce the risk of major adverse cardiovascular events—cardiovascular death, myocardial infarction, and stroke—in adults with type 2 diabetes and established cardiovascular disease, based on final results from the SURPASS-CVOT study; this extension, if approved, would meaningfully expand tirzepatide’s clinical role beyond glycaemic management. Secukinumab (Cosentyx) is under assessment for inclusion of polymyalgia rheumatica in its indication, based on primary analysis from the CAIN457C22301 Phase 3 trial—a development of significance given the current limited therapeutic repertoire for this condition beyond glucocorticoids. Obinutuzumab (Gazyvaro) is similarly under assessment for systemic lupus erythematosus, based on the Phase III ALLEGORY study. Glecaprevir/pibrentasvir (Maviret) is under assessment for an extension covering acute hepatitis C infection, based on the final results from the M20-350 study, which would provide a formally approved option for the early treatment phase of HCV infection. Upadacitinib (Rinvoq) is under assessment for two additional indications—severe alopecia areata and non-segmental vitiligo in adults and adolescents aged 12 and older—while inclisiran (Leqvio) is under assessment for extension to paediatric patients aged 12 to 18 years with heterozygous and homozygous familial hypercholesterolaemia, based on the ORION-16 and ORION-13 trials respectively.
Recent Research Highlights
Three publications in high-impact journals this week are relevant for clinical and public health practice. A prospective Dutch study published in JAMA (Ravensberg et al., 2026) enrolled 370 community-dwelling adults aged 60 years and above on stable levothyroxine doses (≤150 µg/day) and subjected them to protocol-driven stepwise dose reduction. After one year, 25.7% (95% CI: 21.5–30.4%) successfully discontinued levothyroxine while maintaining TSH below 10 mIU/L and free thyroxine within the reference range. The success rate was substantially higher among the subgroup receiving 50 µg/day or less, where 63.6% successfully discontinued treatment. Given the very large number of older adults who receive levothyroxine—frequently initiated for subclinical hypothyroidism and continued indefinitely—these findings provide a clinically actionable basis for considering structured deprescribing trials, particularly in patients on lower doses. Quality of life showed no significant deterioration among those who successfully discontinued.
A systematic review published in the BMJ (Doyon-Plourde et al., 2026) evaluated human evidence on potential health effects of aluminium-adjuvanted vaccines across 59 studies. High-certainty evidence from randomised controlled trials and large cohort studies consistently demonstrated no association between aluminium-adjuvanted vaccines and serious or long-term health outcomes, including asthma, autism spectrum disorders, and other chronic conditions. Studies on macrophagic myofasciitis were methodologically limited and insufficient to establish causality. The most consistently documented adverse effect was persistent nodules or granulomas following diphtheria-tetanus-pertussis vaccination—uncommon, localised, self-limited, and classified as delayed-type hypersensitivity reactions. These findings provide high-quality reassurance regarding the safety profile of one of the most widely used adjuvant systems in vaccination programmes globally.
Finally, the 13-year follow-up of the multinational colonoscopy screening randomised controlled trial (Kaminski et al., The Lancet, 2026) reported that a single colonoscopy reduced colorectal cancer incidence by 19% (RR 0.81; 95% CI 0.71–0.90) in intention-to-screen analysis and by 45% in per-protocol analysis (RR 0.55; 95% CI 0.33–0.81). The benefit was substantially larger for distal than proximal colorectal cancer. Colorectal cancer mortality remained non-significantly reduced (intention-to-screen RR 0.88; 95% CI 0.68–1.08), with the important observation that background mortality in the no-screening group was substantially lower than anticipated at trial design (0.47% observed vs 0.82% projected), likely reflecting improvements in treatment over the study period. These findings reinforce the incidence-reducing benefit of colonoscopy screening while highlighting that mortality benefits may require longer follow-up to fully manifest.
Infectious Diseases: Global Perspective
Respiratory and Contact Transmission
Andes Hantavirus Outbreak (MV Hondius Cruise Ship, South Atlantic)
The most significant global infectious disease event of Week 19 is a novel Andes hantavirus cluster associated with passengers and crew aboard the Dutch-flagged cruise ship MV Hondius, reported to WHO on 2 May 2026. As of 8 May, eight cases have been reported—six confirmed, two probable—with three deaths, yielding a case fatality ratio of 38%, consistent with the historically documented upper range for hantavirus cardiopulmonary syndrome (HCPS) caused by Andes virus (ANDV). All six laboratory-confirmed cases have been identified as ANDV by RT-PCR or sequencing, with no alternative hantavirus species identified. Four patients remain hospitalised across three countries: one in intensive care in Johannesburg, South Africa, two in hospitals in the Netherlands, and one in Zurich, Switzerland.
Hantavirus cardiopulmonary syndrome is caused by viruses of the genus Orthohantavirus (family Hantaviridae). Andes virus, transmitted by the long-tailed pygmy rice rat (Oligoryzomys longicaudatus), is the predominant cause of HCPS in South America and is uniquely distinguished among hantaviruses by documented, albeit limited, human-to-human transmission. The natural reservoir is sylvatic and restricted to the Andes and Patagonian regions of southern South America. Human infection typically results from contact with infected rodent excreta or contaminated surfaces; incubation ranges from one to eight weeks. The clinical course of ANDV HCPS is biphasic, beginning with a prodrome of fever, myalgia, and gastrointestinal symptoms followed by abrupt-onset respiratory distress and haemodynamic compromise. Case fatality rates for ANDV HCPS range from 30% to 50% in the Americas, substantially higher than European and Asian hantavirus infections (which cause haemorrhagic fever with renal syndrome and carry case fatality rates typically below 15%).
The working hypothesis, based on the epidemiological timeline, is that the index case (Case 1)—an adult male who had spent more than three months travelling in Argentina, Chile, and Uruguay—most likely acquired ANDV through environmental exposure prior to boarding the ship in Ushuaia on 1 April 2026. Subsequent cases demonstrate epidemiological links to Case 1 during his illness period and symptom onset dates consistent with documented ANDV incubation periods, supporting the hypothesis of limited onboard human-to-human transmission. This mode of transmission, while unusual, has been documented in community settings involving close and prolonged contact with early-phase patients. The ship—which departed Ushuaia with 114 passengers, with six additional passengers boarding at Tristan da Cunha—has nationalities from 23 countries, including multiple EU/EEA member states. As of 8 May, the MV Hondius was sailing toward the port of Grandilla, Tenerife, with expected arrival on 10 May; disembarkation is planned under coordinated health screening and infection control procedures.
Zoonotic and Animal Disease Events
Highly Pathogenic Avian Influenza H5N1 (Global)
WOAH follow-up reports published this week document ongoing H5N1 highly pathogenic avian influenza (HPAI) activity across multiple continents. In North America, the United States continues to report ongoing H5N1 activity in both wild birds and poultry (FUR_218 in operation since December 2021), and Canada has reported H5N1 in poultry (FUR_100) dating to September 2023. In South America, Chile reports H5N1 in poultry as of March 2026, Brazil reports H5N1 in non-poultry wildlife, and Peru has detected H5N1 (H5, N-untyped) in non-poultry wildlife. In Europe, Poland remains the most heavily affected country, with numerous concurrent follow-up reports documenting H5N1 in wild birds across multiple foci. The United Kingdom, Spain, the Czech Republic, Denmark, Austria, Iceland, and Switzerland also have active H5N1 events in wild birds. Japan reports continued H5N1 in poultry since October 2025, and Montenegro reports its first occurrence in poultry. While the current HPAI situation does not involve documented human cases in these follow-up reports, the geographic breadth of wild bird involvement creates sustained spillover risk for poultry holdings and is a standing precondition for the rare occurrence of human infection, justifying continued epidemiological vigilance.
New World Screwworm in Mexico
Multiple follow-up reports from Mexico document the ongoing spread of Cochliomyia hominivorax (New World screwworm), an obligate parasite causing myiasis in warm-blooded animals. Reports from March, April, and late April 2026 document first occurrences in multiple zones and compartments, indicating progressive geographic expansion. While this is primarily a veterinary and agricultural concern—screwworm infestations cause severe tissue destruction in livestock and, rarely, in humans—the extension toward the North American border has raised concern at the US regulatory level. Continued spread could have significant implications for livestock trade.
Foot-and-Mouth Disease in Greece
Of particular regional relevance, Greece reported foot-and-mouth disease (FMD) serotype SAT 1 (FUR_6) in March 2026, constituting a recurrence of an eradicated disease in an EU member state. FMD SAT 1 is a serotype historically associated with sub-Saharan Africa and sporadically with the Middle East and North Africa; its detection in Greece is epidemiologically unusual and represents a significant animal health event. It is reinforced by concurrent follow-up reports of sheep pox and goat pox in Greece (FUR_28) and Romania (FUR_3). FMD is not a zoonotic disease and does not directly threaten human health; however, it poses substantial threats to livestock populations, trade, and agricultural economies. Bulgaria shares a land border with Greece, and the detection of FMD SAT 1 in a neighbouring EU member state has direct implications for Bulgarian veterinary surveillance and livestock movement controls.
Infectious Diseases: European Union / European Economic Area
Respiratory Virus Epidemiology
The EU/EEA is in a late-season to inter-seasonal respiratory virus period. In Week 18, consultation rates for acute respiratory illness (ARI) in primary care were reported by 15 countries at medium electronic monitoring levels (MEM) with 9 countries at baseline, and ILI consultation rates in 17 countries similarly showed 16 at baseline. Influenza test positivity in primary care was 0.9% (pooled median; IQR 0–3%) in Week 18—a figure consistent with inter-seasonal background levels. Influenza intensity was classified as low in four countries and baseline in 16 of 20 reporting countries, with geographic spread predominantly sporadic (11 countries) or no activity (five countries). RSV remains the primary contributor to respiratory virus activity, though circulation is low and declining; RSV test positivity in hospitals was 5.8% (IQR 7.4–5.7–12%), with the pace of decline slightly slowing compared with recent weeks, suggesting the tail of the RSV season is prolonged. SARS-CoV-2 activity shows early signals of sustained primary care transmission in some countries, with pooled primary care test positivity of 2.1% (IQR 1.1–0–3.3%) and hospital test positivity of 0.8% (IQR 0.3–0–0.9%), both remaining at very low levels across all age groups. The variant landscape is stable, with BA.3.2 (variant under monitoring) accounting for all detected SARS-CoV-2 variants in the most recent two-week reporting window.
Fecal-Oral Transmission
Salmonella Stanley ST2045 Multi-Country Cluster
ECDC is coordinating a multi-country investigation of a Salmonella Stanley ST2045 cluster that has now accumulated 62 cases reported between January and 6 May 2026 from ten countries: Austria, Czechia, Denmark, Estonia, France, Germany, Lithuania, the Netherlands, the United Kingdom, and the United States. The cluster was first identified following notification by Denmark through EpiPulse. Children and young adults are disproportionately represented among cases, and hospitalisations have been reported. Whole-genome sequencing of available isolates demonstrates a tight genetic cluster—exclusively human isolates so far—consistent with a likely common source of exposure, though no food vehicle or environmental source has been identified despite ongoing parallel investigations. The temporal distribution spans four months, which is atypical for a point-source outbreak and may suggest ongoing exposure through a persistently contaminated source or intermittent distribution of a contaminated product. The predominance of younger age groups raises the possibility of a food item with a demographic exposure pattern skewed toward children and young adults—consistent with categories such as packaged snacks, confectionery, or school-distributed foods—though this remains speculative pending case interviews and exposure assessments.
Contact and Sexual Transmission
Mpox (EU/EEA)
In March 2026, 80 mpox clade I cases were reported by ten EU/EEA countries, with Spain contributing the largest share (23 cases) followed by Germany (19 cases). This follows 89 cases in January and 78 cases in February, indicating relatively stable clade I transmission at low but persistent levels. Clade II activity was lower: 22 cases from seven countries in March (Spain 11, Germany 4, Netherlands 3), following 63 cases in February and 98 in January. Over the past twelve months, 15 countries reported 336 clade I cases and 17 countries reported 1,016 clade II cases. The epidemiological profile is consistent across both clades: 95% of clade I and 92% of clade II cases with complete data were reported among men who have sex with men (MSM); hospitalisation rates remain low (14% for clade I, 7% for clade II); and vaccination uptake remains insufficient—72% of clade I cases and 77% of clade II cases were unvaccinated. One death in a clade II case was reported in the past twelve months; no clade I deaths have been reported in the EU/EEA. Denmark and Slovakia have notified their first clade I cases through event-based surveillance, indicating ongoing spread to previously unaffected countries. With the approach of spring and summer, and the associated increase in travel and attendance at mass gathering events including Pride celebrations, ECDC anticipates elevated risk for further spread; ECDC maintains its October 2025 risk assessment of moderate risk for MSM and low risk for the general EU/EEA population for clade Ib, with very low for clade IIb in the general population.
Vector-Borne and Zoonotic Disease
Hantavirus Cruise Ship — EU/EEA Risk Assessment
The ANDV cruise ship cluster (described in the global section) carries direct EU/EEA relevance given the multinational composition of the MV Hondius passenger and crew manifest, which includes individuals from Belgium, France, Germany, Greece, Ireland, the Netherlands, Poland, Portugal, and Spain, among others. ECDC has published a Threat Assessment Brief (6 May 2026) and is supporting response operations through the EU Health Task Force (EUHTF), coordinating with member states, WHO, and the European Commission. Contacts from the ship have been identified in the United Kingdom (7), Canada (3), Chile (2), Singapore (2), and other countries, and health monitoring is ongoing. ECDC’s assessment explicitly notes that the ANDV reservoir (Oligoryzomys rodent species) is not present in Europe, so introduction into the European rodent population and subsequent sylvatic transmission cycles are not anticipated. Even if transmission from disembarking passengers were to occur, the documented requirement for close and prolonged contact for ANDV human-to-human spread makes widespread community transmission unlikely. The risk from this outbreak for the EU/EEA general population is assessed as very low.
Infectious Diseases: Bulgaria
Respiratory and Droplet Transmission
Varicella
Week 19 recorded 709 varicella cases—an increase of 277 cases over Week 18 (+64% week-over-week)—the largest single-week rise of the 2026 surveillance year to date. The year-to-date cumulative total reaches 11,650 cases, a modest 1.4% excess over the 11,494 cases recorded in the same period of 2025, indicating that the 2026 season’s overall trajectory remains broadly comparable to the prior year, but is clearly in an accelerating late-spring phase. Regional distribution from the ZRZ Week 19 data is highly dispersed: Sofia-grad (208 cases) contributes nearly 30% of the national total, followed by Plovdiv (35), Varna (28), Haskovo (48), Shumen (8), Kyustendil (33), and Gabrovo (25), with cases documented in virtually all districts. The geographic universality of the distribution is consistent with varicella’s high transmissibility (R₀ estimated at 10–12 in susceptible populations) and reflects the ongoing accumulation of susceptible cohorts in a country that has not implemented universal childhood varicella vaccination. Varicella (Varicella-zoster virus) is transmitted via respiratory droplets and direct contact with lesions, with an incubation period of 10–21 days; complications—including secondary bacterial superinfection, varicella pneumonia, and cerebellar ataxia—occur most frequently in adults and immunocompromised individuals and are preventable by vaccination.
Measles
The ZRZ regional distribution data for Week 19 documents 33 measles cases distributed across four districts: Pleven (16 cases), Vracha (11 cases), Lovech (3 cases), and Kyustendil (3 cases). This represents the first substantial measles signal in Bulgarian national surveillance during the 2026 year and is epidemiologically notable for two reasons. First, the geographic concentration in Pleven and Vracha—two adjacent districts in north-central Bulgaria—suggests active chains of transmission within a defined sub-regional area rather than independent importations, raising the possibility of an ongoing outbreak. Second, measles virus (Morbillivirus hominis), transmitted exclusively via the respiratory route and airborne spread with one of the highest known basic reproduction numbers of any pathogen (R₀ of 12–18), requires population immunity above 95% to prevent sustained transmission—a threshold that Bulgarian routine immunisation has historically approached but not uniformly maintained across all districts and age cohorts. Complications of measles include pneumonia (the leading cause of measles deaths), encephalitis (occurring in approximately 1 in 1,000 cases), and subacute sclerosing panencephalitis (a fatal late neurological complication occurring years after acute infection). In populations with vitamin A deficiency or HIV co-infection, case fatality can reach 10–15%. No prior measles cases have been reported in the NCIPD national operational analysis for the preceding weeks of 2026, making this Week 19 signal the year’s inaugural indication of potential local measles transmission. Rapid investigation of the Pleven-Vracha-Lovech cluster—including case-based investigation, vaccination status ascertainment, and genotyping of available specimens—is warranted.
Scarlet Fever
Week 19 registered 57 scarlet fever cases, a five-case decline from Week 18 (−8% week-over-week). The year-to-date total of 1,337 cases is 28% below the 1,867 cases recorded in the same period of 2025, suggesting that the 2026 scarlet fever season is tracking substantially below the prior year’s burden. The mild week-over-week decrease combined with the ongoing downward trend supports the interpretation that scarlet fever activity, caused by Group A Streptococcus pyogenes via the respiratory route, is in a seasonal waning phase as the school calendar approaches its late-spring conclusion. The ZRZ data documents cases in 16 districts, with Sofia-grad (16), Plovdiv (12), and Varna (4) contributing the largest shares.
Fecal-Oral Transmission
Gastroenteritis and Enterocolitis
The most prominent fecal-oral signal in Week 19 is a 34% week-over-week rise in acute gastroenteritis and enterocolitis to 185 cases (from 138 in Week 18), with cases comprising 70 possible, 110 probable, and five confirmed. The year-to-date total of 2,815 cases modestly exceeds the 2,727 cases reported through the corresponding period of 2025 (+3.2%), suggesting a slight but not dramatic increase in the annual baseline. The week-over-week increase of 47 cases exceeds the 20% inclusion threshold and warrants monitoring: May corresponds to the beginning of the period during which food-borne and water-borne transmission pathways intensify due to rising ambient temperatures. The ZRZ regional breakdown attributes the largest concentrations to Varna (29 cases), Plovdiv (37), Stara Zagora (27), Sofia-grad (27), and Kyustendil (9). Cases are broadly distributed, suggesting multiple independent transmission chains rather than a single focal outbreak.
Campylobacteriosis
Campylobacteriosis registered 13 confirmed cases in Week 19, a four-case increase over Week 18 (+44% week-over-week). The year-to-date cumulative total of 202 cases is 127% above the 89 cases recorded in the same period of 2025—the largest proportional year-over-year excess among all enteric pathogens currently monitored in Bulgaria. This excess has been sustained without interruption since the beginning of 2026 and has been documented consistently across the preceding weeks of this report series. Campylobacter jejuni and C. coli are primarily acquired through consumption of undercooked poultry, contaminated water, or direct contact with animal reservoirs; the resulting illness manifests as self-limited enteritis with fever, abdominal cramps, and diarrhoea, though bacteraemia, reactive arthritis, and Guillain-Barré syndrome complicate a minority of cases. The persistence and magnitude of the year-over-year excess continue to suggest a systemic change in either exposure patterns, laboratory ascertainment, or reporting completeness that has not yet been elucidated through formal epidemiological investigation.
Vector-Borne Transmission
Lyme Borreliosis
Six confirmed cases of Lyme borreliosis were registered in Week 19, a three-case increase from Week 18 (+100% week-over-week). The year-to-date total of 60 cases is 14% below the 70 cases reported in the same period of 2025. The doubling of weekly case counts from three to six is consistent with the expected onset of peak tick activity in Bulgaria during May, when Ixodes ricinus populations reach their highest questing density. Cases this week were distributed across Gabrovo (2), Lovech (3), and Shumen (1), districts with significant mixed deciduous forest coverage and known tick exposure risk. Lyme borreliosis—caused by Borrelia burgdorferi sensu lato and transmitted by Ixodes spp. ticks—manifests initially as erythema migrans in 70–80% of cases, with disseminated infection involving the nervous system, heart, and joints occurring in untreated patients. Surveillance data in May and June will be the key indicator of the 2026 tick season’s intensity relative to prior years.
Marseille Fever
One confirmed case of Mediterranean spotted fever (Marseille fever), caused by Rickettsia conorii and transmitted by the brown dog tick (Rhipicephalus sanguineus), was registered in Week 19, consistent with the previous week. The year-to-date total of three cases is substantially below the ten cases recorded through the same period of 2025. Activity is expected to increase progressively through summer as tick populations expand.
Contact and Sexual Transmission
Syphilis
Week 19 recorded 14 confirmed syphilis cases, a nine-case increase from Week 18—a 180% week-over-week surge that represents the most dramatic single-week increase in this category during the 2026 surveillance year. The year-to-date total of 138 cases is 9% above the 127 cases registered in the same period of 2025, a modest but consistent excess. Congenital syphilis, reported separately, has accumulated 14 cases year-to-date versus 12 in the same period of 2025, representing a 17% year-over-year increase and a continued burden of preventable vertical transmission. Single-week fluctuations in syphilis notifications are common given the variable lag between diagnosis, confirmation, and reporting; however, a surge of this magnitude warrants monitoring over the following two to three weeks to determine whether it reflects a reporting consolidation artefact or an underlying acceleration in local transmission.
Gonorrhea
Four confirmed cases of gonorrhea were registered in Week 19, one more than Week 18 (+33% week-over-week). The year-to-date total of 89 cases represents a 218% excess over the 28 cases registered in the same period of 2025. This is the most pronounced sustained year-over-year increase among tracked infections in Bulgaria for 2026 and has been documented without interruption since Week 1. As previously noted in this report series, Bulgarian routine surveillance does not report antimicrobial susceptibility data alongside gonorrhea case notifications, representing a structurally significant gap given the global emergence of extensively drug-resistant Neisseria gonorrhoeae strains and the clinical implications of treatment failure.
Urogenital Chlamydial Infection
Two confirmed cases of urogenital chlamydial infection were registered in Week 19, two fewer than in Week 18 (−50% week-over-week). Despite this single-week decline, the year-to-date total of 117 cases is 149% above the 47 cases registered in the same period of 2025. Chlamydia trachomatis infection, the most commonly reported sexually transmitted infection in EU/EEA countries, is frequently asymptomatic—particularly in women—leading to systematic under-ascertainment. The sustained year-over-year excess may reflect genuine increases in transmission, expanded testing availability, or improved reporting completeness, and likely represents some combination of all three.
HIV
Five confirmed HIV cases were registered in Week 19, unchanged from Week 18. The year-to-date total of 86 cases is 24% below the 113 cases recorded in the same period of 2025. While this apparent decline may partially reflect improvements in earlier diagnosis (which could reduce the pool of newly detectable late-stage infections), or reporting delays, Bulgaria’s HIV surveillance context is characterised by late diagnosis in a substantial proportion of cases, which limits the interpretation of week-to-week and year-over-year notifications as a direct indicator of incidence.