Lessons Learned During 2024‒25 Highly Pathogenic Avian #Influenza #H5N1 Virus #Outbreak Response in #USA: Experience of State and Local Public Health Departments

 

Abstract

Objectives. 

To describe challenges and lessons learned during state and local health department responses to the 2024‒2025 highly pathogenic avian influenza A(H5N1) outbreaks.

Methods. 

We conducted semistructured interviews from August to November 2025 with Department of Health and Agriculture staff from states with confirmed or probable A(H5N1) human cases. We conducted 15 total interviews with 37 participants from 10 US states. Interview transcripts were inductively and deductively coded to identify generalizable lessons that might improve future outbreak response efforts.

Results. 

Key themes included difficulty accessing farms and reaching at-risk populations; lack of sufficient guidelines for proactively responding to zoonotic outbreaks that could have human health implications; the importance of maintaining preparedness planning, capacity, and infrastructure; and uncertainty around future capacity to respond to outbreaks because of resource constraints and changes in federal leadership.

Conclusions. 

Although this study focused on responses to A(H5N1) outbreaks, the findings are indicative of the nation’s overall readiness for biological threats. Prioritization of capacity building for infectious disease outbreaks, including robust health department funding to support continued disease surveillance, is critical to prevent more widespread transmission. 

(Am J Public Health. Published online ahead of print September 3, 2026:e1–e7. https://doi.org/10.2105/AJPH.2026.308656)

Source: 

Link: https://ajph.aphapublications.org/doi/10.2105/AJPH.2026.308656

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#Italy, #WNV & #Usutu Virus Weekly #Surveillance #Report No. 6 (ISS, Sept. 4 '26): 521 human cases so far this season, 26 fatal

 

{Excerpt, Summary}

(...)

    ° Since the beginning of the epidemic season and as of September 2 '26, 521 human cases of confirmed infection with West Nile Virus were reported. They were 432 in the last week report. 

        § Of these, 269 were WNND (West Nile Neuroinvasive Disease), of which 4 were imported: 1 from Maldives, 1 France, 1 Belgium and 1 Greece; 

        § 70 cases were detected among blood donors; 

        § 179 cases were of West Nile Fever (1 case imported from Burkina Faso), 

        § 2 cases were of unspecified nature; 

        § 1 case was asymptomatic. 

    ° The number of affected provinces has risen to 75 in 19 Regions.

    ° Among confirmed cases, 26 fatalities have been recorded. The Case-Fatality Rate is now at 9.4% (during 2025, it was 14.6%).

    ° So far this season, 10 human cases of infection with Usutu virus have been confirmed (6 in Lombardy, 1 Emilia-Romagna, 1 Marche, 1 Latium, 1 Piedmont).

(...)

Source: 

Link: https://www.epicentro.iss.it/westnile/bollettino/Bollettino_WND_2026_6.pdf

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Experimental #reproduction numbers disentangle #vaccine effects on susceptibility and infectiousness during #H5N1 #transmission in #geese

 

Abstract

Vaccination against high pathogenicity avian influenza virus (HPAIV) is increasingly used to protect poultry, but vaccine performance is commonly inferred from clinical protection and virus shedding rather than measured transmission. We asked whether reproduction numbers from controlled transmission experiments can quantify how vaccination changes susceptibility and infectiousness. Domestic geese were prime-boost vaccinated with an H5 clade 2.3.4.4b RNA-replicon vaccine and challenged with homologous HPAIV H5N1. Replicated seeder-sentinel groups represented transmission among unvaccinated animals, to vaccinated contacts, and from vaccinated breakthrough-infected animals. Vaccinated directly challenged geese remained clinically protected although all became RT-qPCR-positive. Estimated reproduction numbers were R0=4.7 (95% CI, 2.8-8.0) among unvaccinated geese, Rs=2.6 (1.6-4.5) for transmission to vaccinated contacts, Ri=3.7 (2.0-6.8) for transmission from vaccinated infected geese, and Rvacc=2.0 (0.8-4.9) for a fully vaccinated population. Vaccination reduced transmission but did not reduce the point estimate for Rvacc below one under these intensive exposure conditions. Vaccinated infected geese also shed substantially less viral RNA, whereas the estimated reduction in infectiousness was more modest, indicating that RNA shedding alone may not reliably predict transmission reduction. Experimental reproduction numbers therefore provide a direct population-level complement to conventional vaccine endpoints and separate effects on susceptibility from effects on onward transmission.

Competing Interest Statement

Christophe Cazaban is an employee of CEVA Santé Animale, which provided the experimental vaccine used in this study. The remaining authors declare no competing interests.

Source: 

Link: https://www.biorxiv.org/content/10.64898/2026.09.02.748824v1

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#Chile - #Influenza A #H5N1 viruses of high pathogenicity (Inf. with) (non-poultry including wild birds) (2017-) - Immediate notification

 

Backyard captive birds in Los Lagos Region.

Source: 

Link: https://wahis.woah.org/#/in-review/7802

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Immunogenicity and #safety of seasonal #influenza #vaccine co-administered with other vaccines: a systematic review and meta-analysis

 

Abstract

Seasonal influenza remains a leading cause of global morbidity and mortality, highlighting the need for vaccination strategies that improve coverage and streamline vaccine delivery. In this systematic review and meta-analysis, we searched PubMed, Embase, Web of Science, Scopus, and the Cochrane Central Register of Controlled Trials for randomised controlled trials (RCTs), cohort, case-control, and cross-sectional studies, evaluating immunogenicity and safety of same-day co-administration of influenza vaccines with COVID-19 or other vaccines, compared with non-concomitant administration. Comparators included sequential administration, single vaccine administration or placebo-controlled delayed vaccination. Risk of bias was evaluated using the Cochrane Risk-of-Bias tool for Randomized Trials and Risk of Bias In Non-randomized Studies of Interventions; certainty of evidence was evaluated using Grading of Recommendations, Assessment, Development and Evaluation. Immunogenicity was assessed using geometric mean fold rise (GMFR) in antibody titres and seroprotection rate. Safety was assessed by adverse event (AE) incidence. 52 eligible studies were included. Influenza immunogenicity was comparable between the co-administration and non-concomitant comparator group across all strains (H1N1 GMFR ratio of means (ROM): 1.02 [95% CI: 0.95–1.10]; H3N2, 1.05 [95% CI: 0.97–1.13]; B strain, 1.01 [95% CI: 0.97–1.05]). Pooled risk ratio (RR) for seroprotection was 1.00 for all three strains with 95% CIs ranging from 0.99–1.01. GMFR for COVID-19 vaccines was modestly reduced under co-administration (ROM 0.84 [95% CI: 0.74–0.95]; p = 0.006). Serious AEs were more frequent in the co-administration group compared to the non-concomitant group (RR 1.41 [95% CI: 1.07–1.86]; p = 0.014; absolute risk difference: 1.56 percentage points). Overall, co-administration preserves influenza immunogenicity but modestly reduces COVID-19 vaccine GMFR. Although safety findings warrant cautious interpretation, the low absolute risk difference supports its feasibility as a strategy to streamline vaccination schedules and improve uptake.

Source: 

Link: https://www.nature.com/articles/s41541-026-01548-z

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#Ring and #community #vaccination for #Bundibugyo virus #outbreak response: a stochastic network modelling study

 

Summary

Background

Vaccination with rVSV-ZEBOV is highly effective against Ebola virus, but protection against Bundibugyo virus (BDBV) is unproven. We evaluated the relative population impact and dose efficiency of a partially cross-protective hypothetical vaccine under operationally realistic constraints during a BDBV outbreak.

Methods

We developed a stochastic transmission model on a clustered household–community contact network with empirically realistic local structure, calibrated to 2026 DR Congo BDBV outbreak data. Time-varying effective reproduction numbers were estimated using a Bayesian renewal model. We evaluated case detection, isolation, contact tracing, reactive ring vaccination (Ring 1: direct contacts of the index case; Ring 2: contacts of contacts), and community vaccination (20–80% coverage). Base-case vaccine effectiveness was 45% and included post-exposure protection against disease and mortality. Primary outcomes were mortality and incidence reductions, total doses, and dose efficiency (doses per death averted) over 90 days, evaluated in a probabilistic sensitivity analysis with 10 000 matched stochastic replicates per strategy.

Findings

Compared with base operations alone (30% detection, 30% tracing), enhanced operations alone (70% detection, 80% tracing) reduced expected mortality by 81·6% (95% uncertainty interval 73·1–87·7). Reactive Ring 2 vaccination under base operations reduced mortality by 24·6% (18·0–29·6), requiring 35·1 doses per death averted. Added to enhanced operations, Ring 2 vaccination reduced mortality by 83·6% overall (76·4–89·0), an incremental benefit of 10·5% (6·2–15·6) beyond enhanced operations alone. Community vaccination at 20%, 40%, 60%, and 80% coverage reduced mortality by 44·7% (34·8–52·5), 67·4% (56·2–74·3), 79·8% (70·4–85·3), and 86·6% (79·2–90·4), respectively, requiring 53·8–111·4 doses per death averted.

Interpretation

Strengthened case finding, contact tracing, and isolation averted most deaths even without vaccination. Once these operations were strong, reactive ring vaccination added a modest further benefit, whereas rapid community vaccination produced the largest reductions in simulated scenarios but required substantially more doses. A partially protective BDBV vaccine's population-level value will depend principally on rapid, broad delivery.

Funding

Canadian Institutes of Health Research.

Translation

For the French translation of the abstract see Supplementary Materials section.

Source: 

Link: https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(26)00464-0/fulltext

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#WHO emergency #guidance on use of licensed #Ebola {Zaire} #vaccine during #Bundibugyo virus disease #outbreaks - Interim guidance 31 August 2026 (Summary)

 

Context

    Ervebo® is currently the only licensed Ebola vaccine available. Ervebo®  (rVSV-EBOV-GP) is a live, recombinant vesicular stomatitis virus (rVSV)-based vaccine licensed that was prequalified by the World Health Organization (WHO) in 2019 for the prevention of Ebola virus disease caused by Ebola virus (EBOV, species Orthoebolavirus zairense, previously known as Zaire ebolavirus) in individuals aged one year or older. It is not licensed for use against Bundibugyo virus (BDBV) and therefore the use of Ervebo® against BDBV constitutes off-label use{1} BDBV and EBOV cause Ebola disease that is  clinically similar but are genetically and antigenically distinct virus species. Their  glycoproteins share approximately only 60–65% amino acid sequence  identity, a distinction that is particularly relevant for vaccination because currently  available Ebola vaccines, including Ervebo®, target the viral  glycoprotein.

    Consequently, although Ervebo® is highly effective against EBOV, the  extent to which Ervebo®-induced immunity provides clinically meaningful  protection against BDBV remains unknown. (1)

    On 19 August 2026 (2), the Strategic Advisory Group of Experts on Immunization (SAGE) reviewed and deliberated on the additional evidence that  had become available following the publication of the WHO emergency guidance  on the use of licensed Ebola virus vaccine during Bundibugyo virus disease  outbreaks, 28 May 2026. (3)

    The BDBV outbreak in the Democratic Republic of the Congo has spread  substantially, with continued transmission and high mortality, creating an urgent  need to strengthen outbreak response and reduce preventable deaths. (4) The  severity of the disease and evolving epidemiological situation increases the  imperative to consider all potentially beneficial interventions, while at the same  time carefully weighing the unknown efficacy of Ervebo® against BDBV, and resultant risks.

    A ring vaccination randomized controlled trial (henceforth referred to as  ring RCT) of Ervebo® and BDBV-specific vaccine candidates is planned to be  conducted in the Democratic Republic of the Congo as a matter of urgency. (5) If  well designed and rigorously implemented, the trial would provide the critical  evidence currently lacking on the efficacy of Ervebo® against BDBV.

Assessment of additional evidence on Ervebo® performance against BDBV since May 2026

    Findings from an increased, albeit still limited, number of studies  conducted to date in nonhuman primates and ferrets suggest some  protection by Ervebo® against BDBV-related mortality, while showing little or no  protection against viraemia and clinical disease (...).

    In the absence of an established correlate or surrogate of  protection  against BDBV, the extent to which findings from animal challenge  models (disease and laboratory-based immunological studies) can predict  protection in humans remains unknown. 

    Available human immunogenicity data regarding potential cross-protection  conferred by Ervebo® against BDBV showed that Ervebo® induces cross-reactive BDBV glycoproteinbinding antibodies which are at levels  approximately 5-fold lower than against EBOV, and that cross-neutralization of  BDBV pseudoviruses with neutralizing titres are approximately 3.5–4-fold lower  than against EBOV (...).

    No Ervebo® vaccine efficacy data against BDBV in humans have been  generated yet. 

    There are a small number of anecdotal reports of previously vaccinated  health care workers who subsequently developed BDBV disease and survived.  However, no conclusions regarding vaccine efficacy or effectiveness can be drawn  from these observations because of the very small sample size, the absence of an  appropriate comparator group, the potential for substantial bias, non-systematic  data collection, and the resulting considerable statistical uncertainty.

    Overall, the limited data and anecdotal reports are suggestive of some  protection against BDBV-related mortality and are consistent in trending towards  some as yet unquantified benefit.

    In conclusion, the available data remain insufficient to determine whether Ervebo® provides any clinically meaningful protection against  BDBV in humans or to reliably estimate the magnitude of such protection,  including protection against infection, disease, severe disease or death.

Benefit–risk considerations regarding off-label use of Ervebo® in the context of unknown efficacy against BDBV

    There is currently clinical equipoise regarding the efficacy of Ervebo®  against    BDBV. 

    Vaccine efficacy in humans remains to be established and could range  from high efficacy, with substantial clinical and public health benefit, through  moderate or partial efficacy, to limited or negligible efficacy, with little or no  meaningful protection. The lower limit of the range of potential effects may even  include harm. The potential ratio of benefits and risks of broader use therefore  differ considerably depending on where within this range the true efficacy ultimately lies.

    If efficacy is high or clinically meaningful, broader use while the ring RCT  is underway could potentially reduce severe disease and deaths and, if the vaccine  also protects against infection and transmission, contribute to outbreak  control. In a context where other medical countermeasures remain limited, earlier  access could provide populations at high risk with a vaccine that has a  well-characterized safety profile, while BDBV-specific vaccines remain under  evaluation and are not yet available for use. Use within appropriately designed  research frameworks could also generate complementary real-world effectiveness  data. In addition, vaccinated individuals would be expected to benefit from  protection against Ebola virus disease should they subsequently be exposed during a future EBOV outbreak.

    Conversely, if efficacy is low, negligible or absent, the balance of benefits  and risks would be substantially less favourable. Considerable financial, logistic  and human resources would be diverted to an intervention providing little or no  clinical or public health benefit. These resources could otherwise support  outbreak-control measures of established effectiveness, including surveillance,  contact tracing, timely testing and case detection, isolation, infection prevention  and control, and safe and dignified burials. These resources could also have been better invested in the development of BDBV-specific vaccines.

    A scenario in which Ervebo® provides meaningful protection against  severe disease or death, but limited or no protection against infection, viraemia or  onward transmission, would require careful consideration. Protection against  severe disease or death would constitute an important individual and public health  benefit, even in the absence of substantial effects on infection or  transmission. However, vaccination could then reduce morbidity and mortality without necessarily interrupting transmission. If this efficacy profile is  not clearly understood and communicated, vaccination could lead to false  reassurance among vaccinated individuals, communities and responders,  potentially reducing adherence to established outbreak-control measures. Such  behavioural changes could offset some of the benefits of vaccination and, if  infection and onward transmission are not sufficiently reduced, could contribute to continued transmission and potentially prolong or exacerbate the outbreak.

    If efficacy proves limited or negligible, substantial numbers of  breakthrough cases or deaths could also undermine public trust in the outbreak  response and confidence in Ebola vaccines, vaccination programmes generally,  and the health sector more broadly. Once broader vaccination has commenced, a  subsequent decision to restrict or discontinue Ervebo® use, if the evidence shows  limited efficacy, could itself create important communication and trust challenges.

    There are also important evidence-generation trade-offs. The use of  Ervebo® outside rigorous research protocols could interfere with the feasibility,  recruitment, implementation and scientific integrity of studies, particularly the ring  RCT, designed to establish vaccine efficacy for Ervebo® and BDBV-specific  vaccine candidates (which are expected to have the potential for better  performance against BDBV). This could delay the generation of the robust evidence needed to guide policy. Observational Ervebo® effectiveness  studies could provide useful complementary information but are inherently more  susceptible to bias and confounding than RCTs and may therefore be more difficult  to interpret or insufficiently robust to resolve the central question of  efficacy. Vaccine effectiveness (VE) studies of vaccines with modest efficacy are  particularly prone to these limitations. Hence the value of any observational study  depends partly on the extent to which its design can ensure that uptake of the  intervention is as close to random as possible and that outcome data are collected  systematically from all participants allowing comparable analysis, thereby reducing selection and information biases. Conversely, if the ring RCT  demonstrates clinically meaningful efficacy of Ervebo® and/or BDBV-specific  vaccine candidates, such a trial would provide a strong basis for rapidly updating  policy and expanding vaccine(s) use to benefit the wider population.

    Extensive reliance on Ervebo® could potentially affect community willingness to participate in future studies or receive BDBV-specific vaccines,  which become especially important if the efficacy of Ervebo® against BDBV is insufficient.

    Finally, widespread deployment would have implications for global vaccine security. Largescale use of available Ervebo® doses against BDBV could  temporarily deplete the International Coordinating Group on Vaccine  Provision stockpile and potentially compromise timely access to vaccine for  response to a future outbreak caused by EBOV, against which Ervebo® has demonstrated efficacy and is licensed.

    Taken together, the uncertainties described above reinforce the importance of obtaining robust efficacy data as rapidly as possible while  carefully weighing the potential benefit of any broader use against its potential negative consequences.

(...)

{1} Use of a vaccine for an unapproved indication (not described in the approved  labelling) or in an unapproved age group, dosage, or route of administration. 

(...)

© World Health Organization 2026. Some rights reserved. This work is available under the CC BY-NC-SA 3.0 IGO licence.

Suggested citation. WHO emergency guidance on the use of licensed Ebola vaccine during Bundibugyo virus disease outbreaks, 31 August 2026. Geneva:  World Health Organization; 2026. https://doi.org/10.2471/B09884

Source: 

Link: https://doi.org/10.2471/B09884

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Early Action #Review of #Detection, Notification, and #Response Timeliness during Cross-Border #Bundibugyo Virus Disease #Outbreak, #Uganda, 2026

 

Abstract

Bundibugyo virus disease (BVD), an Ebola virus species with no licensed vaccine or therapeutic, reemerged in May 2026 as a cross-border outbreak in Uganda and the Democratic Republic of the Congo. During a 2-day workshop, July 8–9, 2026, we conducted an early action review of the outbreak response using the 7-1-7 framework (7 days to detect, 1 day to notify, 7 days to complete early response actions) to assess timeliness and identify bottlenecks and enablers across 9 response pillars. Uganda declared its outbreak on May 15, 2026; by July 8, the country had recorded 20 confirmed cases (15 imported, 5 locally transmitted) and a case-fatality rate of 15%. Uganda met all 3 targets: detection in 6 days, notification in <1 day, and response completion in 2 days. Low clinical suspicion, cross-border data-sharing gaps, fragmented digital systems, and delayed community engagement were common bottlenecks; strong leadership and coordination structures were most cited enablers.

Source: 

Link: https://wwwnc.cdc.gov/eid/article/32/10/26-1411_article

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#France - High pathogenicity avian #influenza #H5N1 viruses (Inf. with) (#poultry) - Immediate notification

 

A farm with vaccinated ducks in Maine-et-Loire Region.

Source: 

Link: https://wahis.woah.org/#/in-review/7800

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Immunogen selection and prior #immunity shape #antibody breadth following immunisation with avian #H5 #hemagglutinin

 

Abstract

Avian influenza A viruses pose a persistent zoonotic threat to humans owing to their expanding host range and high case fatality rates. In particular, viruses from the 2.3.4.4b clade of the H5 subtype have now been detected in over 60 mammalian species, raising serious pandemic concerns. Understanding immune recognition of the H5 hemagglutinin (HA) is therefore critical for effective vaccine design and pandemic preparedness. To understand the breadth of cross-recognition induced by different H5 strains, we selected genetically diverse H5 human isolates from 2003-2023 and assessed neutralising antibody responses elicited by adjuvanted recombinant HA protein-based vaccines in C57BL/6 mice. Neutralisation activity of sera was determined against seven H5 HA variants using pseudotyped viruses and a PR8-reassortant virus in micro-neutralisation assays. Our results showed a wide variety of cross-strain neutralisation across H5 HA antigen variants. The conventional vaccine strain A/Indonesia/05/2005 displayed narrow activity against emerging clade 2.3.4.4b viruses, whereas ancestral variants exhibited cross-neutralisation profiles showing a diversity of breath but with limited potency. Polyvalent H5 HA formulations and nanoparticle-displayed H5 HA platforms substantially broadened cross-neutralisation against diverse H5 strains. To examine the impact of pre-existing immunity on H5 vaccine immunogenicity in mouse models, mice were primed with either seasonal influenza infection or quadrivalent influenza vaccine (QIV) prior to H5 HA immunisation. QIV pre-vaccination, but not prior influenza infection, enhanced subsequent neutralizing responses towards A/Fujian-Sanyuan/21099/2017 (clade 2.3.4.4b) H5. Collectively, our results demonstrate that immunogen selection and prior immunity shape antibody breadth following immunisation with avian A(H5) hemagglutinin.

Source: 

Link: https://www.biorxiv.org/content/10.64898/2026.09.01.748495v1

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#Bundibugyo Virus Disease #Outbreak, #DRC, #Uganda - Situation #Report 16, Data as of 30 August 2026 (WHO, summary): 6,100 cases & 2,950 deaths in DRC

 

{Excerpt, summary}

{Click on Image to Enlarge}

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Event description

Democratic Republic of the Congo

    The Bundibugyo virus disease (BVD) outbreak in the Democratic Republic of  the Congo continues to evolve, characterized by sustained transmission, high mortality and continued geographic expansion. 

    The epidemiological picture is increasingly heterogeneous, with  persistent transmission in established hotspots in Ituri, intensifying transmission  in parts of Nord-Kivu and Haut-Uélé, and the continued emergence of cases in  previously unaffected health zones. 

    Since External Situation Report #15, a further 516 confirmed cases and 270 confirmed deaths have been reported, bringing the cumulative total to 6100 confirmed cases, including 2950 deaths (CFR 48.4%), as of 30 August 2026. 

    The number of affected health zones has increased from 57 to 60 across  six provinces, with Biena and Manguredjipa in Nord-Kivu and Ganga in  Bas-Uélé newly affected since the previous update. 

    Ituri remains the epicentre, accounting for 82.2% of cumulative confirmed  cases, although continued expansion in Nord-Kivu and Bas-Uélé underscores the  increasingly dispersed geographic pattern of the outbreak.

    During the most recent 21 days (10 – 30 August 2026), 1719 confirmed cases were reported nationally. Compared with 1958 cases during the preceding 21-day period (20 July – 9 August 2026), this represents a decrease of 239 cases (−12.2%). This decline should be interpreted cautiously given  potential reporting delays and retrospective data reconciliation and does not, on its own, establish that transmission is declining. 

    The national trend continues to mask substantial geographic heterogeneity.  

    Reported cases declined by 21.6% in Ituri, from 1601 to 1255, but  increased by 33.2% in Nord-Kivu, from 256 to 341, and by 12.4% in Haut- Uelé, from 97 to 109. Consequently, Ituri’s contribution to newly reported cases  fell from 81.8% to 73.0%, while Nord-Kivu’s contribution increased from 13.1% to 19.8% and HautUélé’s from 5.0% to 6.3%. 

    A further 10 cases were reported in Tshopo and four in the newly affected  Bas-Uélé during the latest period. 

    The latest provincial cumulative totals confirm that Ituri remains the  principal focus, but transmission is becoming progressively less concentrated in  the original epicentre.

    During the same period, 939 confirmed deaths were reported nationally,  compared with 1044 deaths during the preceding 21 days, representing a  decrease of 105 deaths (−10.1%). This decline was again driven predominantly  by Ituri, where reported deaths decreased from 809 to 654 (−19.2%). 

    In contrast, deaths increased from 197 to 228 (+15.7%) in Nord-Kivu and  from 37 to 50 (+35.1%) in Haut-Uélé. Consequently, Ituri’s contribution to newly  reported deaths declined from 77.5% to 69.6%, while Nord-Kivu’s increased from  18.9% to 24.3% and Haut-Uélé’s from 3.5% to 5.3%. Tshopo reported four  deaths and Bas-Uélé three during the latest period. Taken together, the decline in  both reported cases and deaths suggests a reduction in the nationally reported  disease burden. However, reporting delays and retrospective data reconciliation  limit interpretation, while simultaneous increases in cases and deaths in Nord-Kivu and Haut-Uélé demonstrate that transmission remains substantial and is  continuing to redistribute geographically.

Figure 1. Daily trend in confirmed Bundibugyo virus disease cases, with seven-day moving average, by date of report, Democratic Republic of the Congo, as of 30 August 2026

{Click on Image to Enlarge}

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(...)

    At health-zone level, the national decline masks substantial  heterogeneity across established and emerging transmission foci. Of the 60  health zones affected since the start of the outbreak, comparison of the two  consecutive 21-day periods shows that reported cases increased in 20 health  zones and decreased in 22. 

    

    A further 10 previously affected health zones reported no confirmed  cases during the latest 21 days (Adja, Kambala, Logo and Mahagi in Ituri; Goma  and Lubero in Nord-Kivu; Rungu in Haut-Uélé; Lubunga and Wanie-Rukula in  Tshopo; and Miti-Murhesa in Sud-Kivu), while incidence was unchanged in one health zone (Bafwasende, Tshopo). 

    Seven health zones were newly affected during the latest 21-day period. 

    In Ituri, the reduction was driven particularly by Mongbwalu, where  reported cases declined from 183 to 44 (−139; −76.0%), and Nizi, from 277 to  182 (−95; −34.3%). 

    Cases also declined in Lita, from 84 to 61 (−23; −27.4%), and Rwampara,  from 242 to 191 (−51; −21.1%). 

    Bunia, however, remained the largest active focus and increased from  363 to 383 (+20; +5.5%). Other Ituri health zones also recorded increases,  notably Mangala, from 53 to 126 (+73; +137.7%), Nia-Nia, from 61 to 80 (+19;  +31.1%), and Bambu, from 31 to 66 (+35; +112.9%). 

    Outside Ituri, transmission  continued to intensify in Nord-Kivu,  particularly in Katwa, where cases increased from 112 to 165 (+53;  +47.3%), and Beni, from 30 to 66 (+36; +120.0%). In Haut-Uélé, Isiro increased  from 18 to 51 (+33; +183.3%) and Wamba from 8 to 48 (+40; +500.0%). 

    These patterns show that the overall decline in Ituri is being driven by  substantial reductions in several established hotspots rather than a uniform  decrease across the province; Bunia remains highly active, while other foci within  Ituri and in Nord-Kivu and Haut-Uélé continue to expand. 

    Reported deaths show a similar geographic redistribution but with  important differences from the case trends. In Ituri, deaths declined substantially  in several established hotspots, including Mongbwalu, Nizi, Lita and Rwampara,  consistent with the reduction in reported cases in these areas. However, mortality  remained substantial in Bunia, while increases in cases in Mangala, Nia-Nia and  Bambu indicate continued transmission within the province despite the overall  decline.

    In Nord-Kivu, increasing mortality accompanied the continued growth  of the Katwa and Beni foci, while in Haut-Uélé the increase in deaths was  concentrated particularly in Isiro and Wamba. 

    Overall, the health-zone  pattern reinforces the provincial analysis:  transmission is declining in several formerly dominant Ituri hotspots but is not  declining uniformly. 

    Interpretation of health-zone mortality trends in Ituri should however  remain cautious, particularly because cumulative death counts have undergone  continuing reconciliation and redistribution across health zones, with 329 confirmed deaths in Ituri awaiting allocation to health zone as of 30 August  2026. 

    Mortality remains high, with 270 confirmed deaths reported during the  last seven days, including 171 (63.3%) in the community and 99 (36.7%) in BVD  treatment facilities. 

    The persistently high proportion of community deaths (defined  as both  deaths at home and at non-BVD health facilities) highlights continued challenges  with early detection, referral and timely access to treatment, while mortality in  BVD treatment facilities may reflect late presentation, quality of care and patient  vulnerabilities, including age, malnutrition and comorbidities; further analysis to  understand the risk factors is underway.

(...)

Uganda and France

    Both Uganda and France have not reported new cases for more than 42  days. The outbreak in these countries is considered over by WHO’s norm of 42  days without any cases. 

Risk Assessment

    According to WHO’s latest Rapid Risk Assessment as of 20 August 2026, the risk of further spread remains very high within the Democratic  Republic of the Congo and high for neighbouring countries sharing land  borders with the country. 

    The assessment reflects sustained transmission, continued geographic  expansion, high mortality, population mobility, insecurity and persistent response  challenges. The risk is considered low elsewhere in Africa and globally. 

    The second IHR Emergency Committee, convened on 18 August 2026, also  reviewed the evolving situation and emphasized that the outbreak remains far  from controlled, and continues to constitute a Public Health Emergency of International Concern.

(...)

Situation interpretation

    The overall decline in reported cases and deaths is encouraging but  does not yet indicate that the outbreak is under control. Transmission is becoming  increasingly heterogeneous, with reductions in several established  hotspots in Ituri occurring alongside expanding transmission in Nord-Kivu and  Haut-Uélé and continued emergence of new affected health zones. 

    Persistently high mortality, particularly community deaths, together with  gaps in contact follow-up, referral and treatment capacity, infection  prevention and control, and community acceptance, continue to create opportunities for transmission. 

    The response should therefore become more anticipatory and  geographically targeted, rapidly shifting surveillance, contact tracing, clinical care,  IPC, community engagement, workforce and logistical capacity towards emerging and intensifying hotspots, while sustaining interventions in areas where transmission is declining to prevent resurgence.

Source: 

Link: https://iris.who.int/bitstreams/22a50ebd-a676-4a82-a40e-7feae57dc1fe/download

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Characteristics and Monitoring of the 2026 #Outbreak of #Ebola Disease Caused by #Bundibugyo Virus — #DRC, August 2026 (MMWR, edited)

 

Summary

    ° What is already known about this topic?

        § In May 2026, an outbreak of Ebola disease caused by Bundibugyo virus was identified in the Democratic Republic of the Congo.

    ° What is added by this report?

        § This ongoing outbreak is now the second largest Ebola outbreak in history. The targets for five critical public health response indicators (case detection alerts, contact tracing, laboratory testing, isolation of infected persons, and safe and dignified burials) have not yet been met, and the outbreak continues to expand rapidly.

    ° What are the implications for public health practice?

        § Substantial improvements in established outbreak control measures are crucial to rapidly detect and diagnose cases and isolate and provide treatment for infected persons, prevent funeral-associated transmission to prevent additional spread, and control this rapidly expanding outbreak.

    The Democratic Republic of the Congo (DRC) Ministry of Public Health declared an Ebola outbreak on May 15, 2026. Two days later, CDC activated its Emergency Operations Center as part of the U.S. government response to this rapidly growing outbreak. This report describes the epidemiologic characteristics and monitoring of the ongoing outbreak in DRC.

Investigation and Outcomes

Background

    The 2026 Ebola DRC outbreak caused by Bundibugyo virus is now the second largest Ebola outbreak ever recorded. As of August 21, 2026, DRC reported 5,458 confirmed cases and 2,606 (48%) confirmed deaths. 

    Compared with previous Ebola outbreaks, the increase in cases in DRC is unprecedented, with approximately 5,000 cases in 100 days (Ebola Outbreak: Current Situation | CDC). 

    Cases have been reported from six of the 26 DRC provinces (Bas-Uélé, Haut-Uélé, Ituri, North Kivu, South Kivu, and Tshop), affecting 57 of 151 health zones in the affected provinces. 

    Ituri province remains the outbreak epicenter, accounting for 84% of reported cases. 

    Strategies known to control Ebola outbreaks include community-based surveillance, case detection alert notifications,* rapid and in-depth case investigations, identification and monitoring of contacts, infection control measures (e.g., prompt isolation of persons with suspected or confirmed Bundibugyo virus disease [BVD]), rapid diagnostic testing, mortality surveillance, and safe and dignified burials (SDBs).†

Data Source

    Operational indicators for five domains have been generated based on experience with previous Ebola outbreaks, including DRC’s 2018 outbreak. Targets reflect the levels necessary to end the outbreak. 

    The DRC Ministry of Public Health prepares publicly available daily situation reports, and CDC abstracts data from these reports to evaluate the established indicators each day. Indicator data are monitored over time to assess the outbreak trajectory. This activity was reviewed by CDC, deemed not research, and conducted consistent with applicable federal law and CDC policy.§

Operational Indicator Analysis

    Nearly all operational indicators remain below identified targets (...). 

    Operational indicator values were calculated for the 21-day period of July 31–August 21. 

    The average percentage of alerts investigated within 24 hours (last reported August 5, 2026) was 83% (target = >90%). 

    An average of 10.6 contacts were identified per confirmed case (target = ≥20), suggesting underreporting and underascertainment of case contacts. 

    The percentage of confirmed new cases previously identified as known contacts (last reported July 12, 2026) was 15%–20% (target = >90%); this suggests that most cases are occurring outside known transmission chains. 

    In addition, more than one half (59%) of confirmed Ebola deaths are occurring outside an Ebola treatment unit (ETU) (target = 0%), suggesting insufficient ETU capacity, fear of ETUs, and ongoing spread through unidentified transmission chains. 

    Laboratory testing was performed for 72% of validated alerts (target = >90%), indicating that a substantial number of suspected cases remain untested. 

    Test positivity was 24%, with a target of 0%. 

    Although the national ETU bed occupancy was 64%, meeting the target of <80%, occupancy varied substantially by health zone, with some facilities unable to isolate all infected persons and reporting occupancies as high as 140%. 

    Fewer than one half (49%) of affected health zones had at least one SDB team (target = 100%). 

    Current data were not available for several response indicators, such as percentage of persons with confirmed BVD receiving prompt isolation (target = >90%) and percentage of deaths with SDBs (target = 100%), underscoring ongoing data gaps in this complex public health response.

Preliminary Conclusions and Actions

    As of August 21, 2026, most operational indicator measures remained below established response targets, and data for others were unavailable, indicating gaps in surveillance, contact tracing, laboratory testing, health care–seeking, isolation, and SDB capacity that limit control of the ongoing outbreak. 

    These missing data and operational gaps, together with continued geographic expansion of the outbreak, a high percentage of deaths occurring outside ETUs, and a low percentage of cases among persons previously identified as contacts, indicate uncontrolled expansion of the outbreak. 

    Public health response activities are complicated by a protracted complex humanitarian emergency in the eastern part of DRC, including armed conflict, limited health infrastructure, population displacement and mobility, and constraints on access to affected communities.

    Containment and control of the 2026 Ebola disease outbreak requires integration and coordination of at least five response areas: 

    1) expansion of community-based surveillance systems ensuring rapid investigation of alerts; 

    2) improvements in contact tracing completeness and timeliness; 

    3) expansion of treatment and isolation capacity in affected health zones; 

    4) increased laboratory testing capacity, enabling prompt case identification; and 

    5) ensuring SDBs in affected health zones.

    

    In addition, collecting robust, high-quality data regarding these operational actions is essential at the health zone level; CDC’s continued support to the DRC Ministry of Public Health and partners with improving data collection is critical. 

    Collecting data at the level of the health zone facilitates timely local outbreak response decisions. 

    Rapidly enhancing international humanitarian coordination and mobilizing global technical, operational, and other needed support are critical for accelerating the response and controlling the outbreak.

CDC 2026 Ebola Response International Epidemiology and Laboratory Task Force

Christine Atherstone, Amy Boore, Vance Brown, Jonathan Bryant-Genevier, Nirma Bustamante, Maestro Evans, James Fuller, Timothee Kinkela, John D. Klena, Thomas C. McHale, Elissa Meites, Emmanuel A. Mensah, Mpingulu Minlangu, Pierre Muhoza, Mike Park, Jaymin Patel, Satish K. Pillai, Anne Purfield, Logan Ray, Jessica N. Ricaldi, Katrin S. Sadigh, Dean Sayre, Trevor Shoemaker, Rachel Snyder, Christina Spiropoulou, Leisel Talley, Alison Todres, Sebastien Tshipamba, Amy Whitesell, Hailey Whitmire, Kristina Wielgosz, Emily Zielinski-Gutierrez, CDC; Democratic Republic of the Congo, Ministry of Public Health.

Corresponding author: Sascha Ellington, frk5@cdc.gov.

Source: 

Link: http://dx.doi.org/10.15585/mmwr.mm7535e1

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#Genome-informed structural #analysis of #polymerase and glycoprotein #adaptation in #H5N1 clade 2.3.4.4b

 

Abstract

Importance

Understanding the molecular mechanisms driving H5N1 clade 2.3.4.4b is critical for pandemic preparedness.

Objective

To characterize the molecular drivers of viral fitness and mammalian adaptability in recent H5N1 viruses by integrating evolutionary dynamics with structural simulations.

Methods

This study analyzed 2,398 H5Nx genomes (2000–2024) through phylogenetic and selective pressure analyses. HA/NA structures were predicted with AlphaFold 3 and evaluated by AutoDock4 docking, whereas polymerase–ANP32A/B complexes were modeled using template-based methods and their binding free energies were estimated using MM/GBSA. Polymerase–ANP32E complexes were predicted with AlphaFold 3 and similarly evaluated by MM/GBSA. The binding affinities (ΔG) for the sialic acid (SA) receptors and human ANP32 proteins were quantified through molecular mechanics/generalized born surface area calculations.

Results

Clade 2.3.4.4b showed significant antigenic drift in the HA receptor binding site, reducing affinity for α2,3-SA and α2,6-SA receptors. On the other hand, the emergence of a full-length stalk N1 NA with second sialic acid-binding site mutations (e.g., N366S) compensated for reduced HA affinity by enhancing the NA binding stability. In the polymerase complex, both the PB2-627E/631L variant (−144.00 kcal/mol; unadjusted p = 0.0058) and the known mammalian-adaptive 627K/631M variant (−144.67 kcal/mol; unadjusted p = 0.0165) showed more favorable predicted human ANP32B binding free energies than the ancestral 627E/631M state (−136.46 kcal/mol).

Conclusions and Relevance

The co-occurrence of HA, NA, PB1, and PB2 signatures was associated with clade expansion and produced structural predictions consistent with altered receptor or ANP32 interactions; experimental validation is required before inferring effects on fitness or zoonotic risk.

Source: 

Link: https://vetsci.org/DOIx.php?id=10.4142/jvs.26088

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Avian #Influenza #Report: August 23 - 29 '26 (Wk 35) (CHP, HK SAR September 1, 2026): 1 New #Human Infection with #H9N2 virus in Anhui, 20 cases so far this year

 

{Excerpt}

(...)

Avian influenza A(H9N2):

    ° Anhui Province {China}:

        § A three-year-old boy with onset on August 3, 2026.

(...)

Source: Centre for Health Protection, Hong Kong PRC SAR, https://www.chp.gov.hk/en/index.html

Link: https://www.chp.gov.hk/files/pdf/2026_avian_influenza_report_vol22_wk35.pdf

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The first high pathogenicity avian #influenza #H5N1 clade 2.3.4.4b incursions in Hunter New England region, NSW, #Australia, June–July 2026

 

Abstract

Two incursions of high pathogenicity avian influenza (HPAI) A(H5N1) clade 2.3.4.4b in vagrant birds were identified in the Hunter New England region of New South Wales, Australia on 28 June 2026 and 10 July 2026. These were the first detections of the virus in New South Wales and occurred shortly after the first Australian detection in June 2026. The Hunter New England Population Health Unit managed human contacts of the infected birds using a contact management system designed and purpose-built by the Unit. We report on the public health response and opportunities for improvement.

Source: 

Link: https://ojs.cdi.cdc.gov.au/index.php/cdi/article/view/3492

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#Report on #influenza viruses received and tested by the #Melbourne #WHO Collaborating Centre for Reference and Research on Influenza during 2025

 

Abstract

As part of its role in the World Health Organization (WHO) Global Influenza Surveillance and Response System (GISRS), the WHO Collaborating Centre for Reference and Research on Influenza in Melbourne (the Centre) received 13,817 human influenza-positive samples during 2025. Viruses were analysed for their antigenic, genetic, and antiviral susceptibility properties. Selected viruses were propagated in qualified cells or embryonated hens’ eggs for potential use in seasonal influenza virus vaccines. Of the 13,817 samples received or processed, influenza A(H1N1)pdm09 viruses predominated, accounting for 46.1% of samples, compared to 21.2% for A(H3N2) viruses and 19.5% for influenza B viruses; one influenza C virus was received. Among viruses analysed at the Centre, the majority of A(H1N1)pdm09 (> 99%) and influenza B (98%) viruses were antigenically similar to their respective WHO recommended vaccine strains for the Southern Hemisphere in 2025. In contrast, only 43% of A(H3N2) viruses were antigenically similar to their respective WHO recommended vaccine strains. Of 3,307 samples tested for susceptibility to the neuraminidase inhibitors oseltamivir and zanamivir, 37 A(H1N1)pdm09 viruses showed highly reduced inhibition by oseltamivir and no influenza viruses tested showed highly reduced inhibition by zanamivir. Of 5,080 samples with sequencing of the polymerase acidic (PA) gene, no genetic markers associated with highly reduced susceptibility to baloxavir marboxil were identified.

Source: 

Link: https://ojs.cdi.cdc.gov.au/index.php/cdi/article/view/3489

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