Detection of Anti- #H5 #Antibodies in People with Exposure to Wild #Birds in Northern #Canada

 

Abstract

Using a commercially available H5 serology assay, we identified a 7.4% (n=5/68) anti-H5 seroreactivity rate among hunters in Northern Canada. All participants reported close contact with wild birds.

Competing Interest Statement

This study was performed outside of JK's duties and responsibilities with the Public Health Agency of Canada.

Source: 

Link: https://www.medrxiv.org/content/10.64898/2026.05.24.26353994v1

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Government of #Canada introduces temporary #border #measures in response to the #Ebola disease #outbreak (PHAC, May 27 '26)

 

May 26, 2026 | Ottawa, Ontario | Public Health Agency of Canada

    In response to the Ebola disease outbreak in the Democratic Republic of the Congo, and increasing risks in Uganda and South Sudan, the Government of Canada is taking decisive action by introducing temporary border measures to reduce the risk of the virus entering and spreading within Canada.

    The Government of Canada intends to suspend immigration documents for residents of countries that have a high or very high risk of outbreak of Ebola disease for the next 90 days beginning May 27, 23:59 EDT. 

    At this time, this includes the Democratic Republic of the Congo, Uganda and South Sudan. 

    This will mean that even those with a previously approved temporary resident visa, electronic travel authorization (eTA) or permanent resident visa will not be allowed to travel to Canada while their immigration document is suspended. 

    During this time, we also intend to temporarily pause making decisions on applications for these documents from residents of these countries.

    The government intends to implement an additional measure effective May 30 at 23:59 pm EDT until August 29, 2026, whereby Canadian citizens, permanent residents, persons registered under the Indian Act, and foreign nationals, who have been in these areas within the previous 21 days and do not have symptoms, will have to quarantine for 21 days. 

    If they do not have a place where they can quarantine safely, they will be provided with an appropriate location. 

    Travellers who have symptoms will be isolated at a hospital for further assessment. These measures are being implemented under the Quarantine Act.

    Those who are already in Canada are not impacted by these measures, and may continue to stay here for their authorized period of stay. 

    As per standard procedure, these travellers were already screened upon their arrival by a Canada Border Services Agency Border Services Officers. 

    Canadian citizens and permanent residents could still return to Canada and would undergo screening at ports of entry upon their arrival.

    While the risk to people in Canada remains low, the Government of Canada is taking a precautionary approach given the severity of Ebola disease and the evolving international situation, including the FIFA World Cup 2026 ™. There has never been a case of Ebola disease imported into Canada and there are currently no cases of Ebola disease in North America.

    The Government of Canada continues to monitor the situation closely and will adjust these measures as needed based on available evidence, including the epidemiological situation in Canada and internationally.

    Travellers are reminded that border measures may change with little notice and are encouraged to check the latest information before travelling at travel.gc.ca.

(...)

Source: 

Link: https://www.canada.ca/en/public-health/news/2026/05/government-of-canada-introduces-temporary-border-measures-in-response-to-the-ebola-disease-outbreak.html

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#Canada, Speaking #Remarks for the Chief Public Health Officer on #Ebola Disease and #Hantavirus Technical #Briefing (May 22 '26)

 

May 22, 2026 | 1:00pm EST

    Thank you for joining us today.

    Before we begin, I want to acknowledge that we are gathered on the unceded traditional territory of the Anishinaabe Algonquin Nation. I would like to take this moment to reflect on the history of Indigenous people and to honour the original stewards of the lands where we live and work.

Situation Update – Ebola Disease

    I will begin today with an update on the Ebola situation in Africa and what it means for Canada. And then, I will provide an update on Andes hantavirus.

    On May 15, Africa's Centres for Disease Control and Prevention declared an outbreak of Ebola disease in the eastern Democratic Republic of the Congo. Cases linked to this outbreak have also been reported in Uganda, including an imported case that was confirmed to be the Bundibugyo virus strain.

    On May 17, the Director General of the World Health Organization declared this outbreak a Public Health Emergency of International Concern due to the evidence of cross-border spread, uncertainty around the true size of the outbreak, the potential for wider regional and global impacts, and the need for global collaboration.

    It is important to be clear: while this is a serious and evolving situation, cases remain localized, and the global risk is low.

    This outbreak is occurring in an area with complex challenges, including proximity to urban centres, security concerns and high levels of population movement associated with mining activity. These factors can increase the potential for spread locally and across borders.

    We recognize the risk for people in the region is high, and our thoughts are with the individuals, families, communities and health workers who are directly bearing the brunt of this challenging outbreak.

    Canada stands ready to assist.

Risk to Canadians

    Based on the Public Health Agency of Canada's rapid risk assessment and in alignment with the World Health Organization, the risk to people in Canada is considered to be low at this time.

    There has never been a case of Ebola disease imported into Canada despite numerous Ebola outbreaks in the affected region.

    I do want to be transparent that, out of an abundance of caution, one individual in Ontario underwent precautionary testing. This individual recently returned from Ethiopia and reported symptoms consistent with a range of illnesses.

    Both initial testing conducted in Ontario and confirmatory testing at the National Microbiology Laboratory were both negative.

    This is a good example of how quickly measures are activated, even when the likelihood of Ebola is very low.

    Ebola disease is transmitted through direct contact with the body fluids of an infected individual who is showing symptoms, or through contact with infected animals or contaminated materials. It is not spread through casual contact, and it does not spread through the air like respiratory viruses.

    Those at highest risk are individuals providing care to patients with Ebola disease, participating in burial practices involving direct contact, or working in healthcare or laboratory settings where the virus is present.

Public Health Response

    While the risk in Canada remains low, we are taking this situation very seriously and are taking a precautionary approach.

    The Public Health Agency of Canada is actively monitoring the outbreak in close collaboration with international partners, including the World Health Organization, as well as provincial and territorial public health authorities.

    At our borders, we have strengthened screening measures. As of May 20, enhanced screening questions have been implemented at airport kiosks for travellers who have been in the Democratic Republic of the Congo or Uganda within the past 21 days.

    Travellers are now asked whether they have been in these countries and whether they are experiencing symptoms or may have been in contact with someone with Ebola disease.

    We have also deployed additional quarantine and screening officers at key airports, and we are maintaining a 24/7 centralized monitoring approach. Signage has been deployed at major airports across the country to ensure travellers know what to do if they feel unwell.

    These measures are supported under the Quarantine Act and are designed to identify potential risks early and ensure that appropriate follow-up actions are taken.

    On Wednesday, a flight was redirected to Montréal due to a passenger of concern. PHAC quarantine officers assessed the individual, determined they were asymptomatic, and appropriate border procedures were followed.

    For travellers, I want to emphasize the importance of checking the Government of Canada's Travel Advice and Advisories before departure.

    Individuals returning from affected regions should monitor their health for 21 days. If symptoms develop, it is critical that they isolate immediately, away from others and contact local public health authorities before seeking in-person care.

Laboratory and Preparedness Capacity

    Canada has strong laboratory and surveillance systems in place.

    Any suspected case in Canada would be immediately reported, with samples sent to the National Microbiology Laboratory in Winnipeg for confirmatory testing. Results are typically available within 24 hours once samples arrive at the lab.

    Our National Microbiology Laboratory continues to play a leading role globally in Ebola research, including work on vaccines, therapeutics, and diagnostics. Canadian scientists were instrumental in the development of the world's first Ebola vaccine, and they continue to contribute to preparedness and response efforts internationally.

International Collaboration

    This outbreak underscores the importance of global collaboration.

    Canada continues to work closely with international partners through established mechanisms such as the World Health Organization and the Global Outbreak Alert and Response Network.

    We stand ready to provide technical expertise and support if requested, as we have done in previous outbreaks. Our shared goal is to contain this outbreak at its source and reduce the risk of further spread.

Hantavirus Update

    I will now turn briefly to the situation regarding Andes hantavirus.

    Canada confirmed a case of Andes hantavirus linked to the MV Hondius cruise ship earlier this month. At this time, there have been no additional cases identified in Canada beyond the initial confirmed case in British Columbia, and all high-risk contacts continue to be monitored by local public health authorities.

    The overall risk to the general population in Canada remains low at this time.

    We continue to take a precautionary approach given the severity of this virus, while recognizing that person-to-person transmission of Andes hantavirus is rare and typically requires close, prolonged contact with someone who is symptomatic.

    Our thoughts are with the individual in hospital in British Columbia and their family. We thank our public health colleagues and the clinical team for the excellent care and support they are providing.

World Health Assembly and International Coordination

    This week, I had the opportunity to attend the World Health Assembly in Geneva, where I met with a number of my global counterparts, to discuss the public health challenges we all face.

    I also met Dr. Ghebreyesus, Director-General of the World Health Organization and members of his senior leadership team who are leading emergency response, including the Ebola response in DRC.

    These discussions reinforced the importance of transparency, timely information sharing, and coordination in responding effectively to emerging public health threats.

    The events of the past several weeks have demonstrated that strong global relationships are not only valuable, they are essential.

Conclusion

    In closing, we have robust systems in place for detection, prevention, and response. We are working in close collaboration with provincial and territorial partners, as well as with international organizations and governments, to ensure a coordinated and effective approach.

    We will continue to provide timely updates and clear guidance as new information becomes available.

    I would like to thank our public health partners across the country, our frontline healthcare workers, laboratory scientists, and our international colleagues for their dedication, expertise, and collaboration.

    Together, we are working to protect the health and safety of people in Canada and around the world.

    Thank you. Merci. Miigwetch.

Source: 

Link: https://www.canada.ca/en/public-health/news/2026/05/speaking-remarks-for-the-chief-public-health-officer0.html

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#Canada, Media #update on #Andes #hantavirus situation: diagnostic tests confirmed the case announced yesterday (PHAC, May 17 '26)

 

Statement | May 17, 2026 | Ottawa, ON

    The Public Health Agency of Canada (PHAC) has confirmed a case of Andes hantavirus in Canada through laboratory testing. 

    This case was reported by the British Columbia Provincial Health Officer on May 16 and was among the passengers on the MV Hondius cruise ship.

    Samples from British Columbia were sent to PHAC’s National Microbiology Laboratory (NML) in Winnipeg for confirmatory testing. 

    One individual’s sample was confirmed positive for hantavirus on May 16. 

    A second individual who was a travelling partner of the confirmed case was confirmed negative by the NML. 

    There have been no further cases identified at this time. 

    All high-risk contacts are isolating and will continue to be monitored closely by local public health.

    PHAC, the province of British Columbia, and local public health are working together to ensure all public health measures continue to be followed to protect the health of Canadians.

    The overall risk to the general population in Canada from the Andes hantavirus outbreak linked to the MV Hondius cruise ship remains low at this time. 

    All confirmed cases to date have been passengers or crew on the MV Hondius cruise ship. 

    Given the severity of this virus, we are taking a precautionary approach to ensure Canadians are protected.

    PHAC provided the information about the positive case to the World Health Organization as part of the International Health Regulations and will share information to support the ongoing global investigation of the outbreak.

    “We want to thank public health authorities and frontline staff in British Columbia for the dedicated care that they are providing and for their ongoing management of the situation, and the passengers for their cooperation with public health direction to help keep others safe," said Dr. Joss Reimer, Chief Public Health Officer of Canada.

    PHAC will continue to actively monitor the situation, provide guidance and support to provincial and territorial public health partners, and share updates as needed.

Contacts: Media Relations, Public Health Agency of Canada, 613-957-2983, media@hc-sc.gc.ca

Source: 

Link: https://www.canada.ca/en/public-health/news/2026/05/media-update-on-andes-hantavirus-situation1.html

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Media #update on #Andes #hantavirus situation (Public Health Agency Canada, May 16 '26): one new case confirmed

 

Statement | May 16, 2026 | Ottawa, ON

    On May 16, 2026, the British Columbia Provincial Health Officer reported that one of the four high risk individuals who was self-isolating and being monitored for symptoms has tested presumptive positive for Andes hantavirus. 

    The person was transported to hospital for assessment and care on May 14 along with their spouse who also has mild symptoms. 

    The couple were passengers on the MV Hondius. 

    Both will remain in isolation in hospital. 

    Out of an abundance of caution, a third individual who was in secure lodging for isolation has been transferred to hospital for assessment and testing.

    All infection prevention and control protocols are being followed, including the use of personal protective equipment by healthcare workers and personnel involved in the repatriation. 

    Those involved in the repatriation are not considered at risk given the public health protective measures that were in place, in addition to the length of time between repatriation and the onset of symptoms.

    Samples have arrived at the Public Health Agency of Canada’s National Microbiology Laboratory (NML) in Winnipeg for confirmatory testing. Results are expected in the next two days.

    The Public Health Agency of Canada, the province of British Columbia, and local public health are working together to ensure all public health measures continue to be followed to protect the health of Canadians.

    The overall risk to the general population in Canada from the Andes hantavirus outbreak linked to the MV Hondius cruise ship remains low at this time. 

    But, given the severity of this virus, we are taking a precautionary approach to ensure Canadians are protected.

    The Public Health Agency of Canada will continue to actively monitor the situation, provide guidance and support to provincial/territorial public health partners and share updates as needed.

Contacts: Media Relations, Public Health Agency of Canada, 613-957-2983, media@hc-sc.gc.ca

Source: 

Link: https://www.canada.ca/en/public-health/news/2026/05/media-update-on-andes-hantavirus-situation0.html

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Oral #Nirmatrelvir – Ritonavir for #Covid19 in Higher-Risk #Outpatients

 

Abstract

Background

Nirmatrelvir–ritonavir has been shown to reduce progression to severe illness from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in unvaccinated high-risk outpatients. The effectiveness of nirmatrelvir–ritonavir in persons who have been vaccinated, infected naturally, or both is unclear.

Methods

In two open-label platform trials (PANORAMIC in the United Kingdom and CanTreatCOVID in Canada), we enrolled higher-risk adults (≥50 years of age or ≥18 years of age with coexisting conditions) in the community who tested positive for SARS-CoV-2 and had been unwell for 5 days or less. The participants were randomly assigned to receive usual care plus nirmatrelvir (300 mg)–ritonavir (100 mg) twice a day for 5 days or to receive usual care alone. The primary outcome was hospitalization or death from any cause within 28 days after randomization.

Results

From December 8, 2021, to September 30, 2024, a total of 3516 participants in the PANORAMIC trial and 716 participants in the CanTreatCOVID trial underwent randomization. In the PANORAMIC trial, 14 of 1698 participants (0.8%) in the nirmatrelvir–ritonavir group and 11 of 1673 participants (0.7%) in the usual-care group were hospitalized or died (adjusted odds ratio, 1.18; 95% Bayesian credible interval, 0.55 to 2.62; probability of superiority, 0.334). In the CanTreatCOVID trial, 2 of 343 participants (0.6%) in the nirmatrelvir–ritonavir group and 4 of 324 participants (1.2%) in the usual-care group were hospitalized or died (adjusted odds ratio, 0.48; 95% Bayesian credible interval, 0.08 to 2.23; probability of superiority, 0.830). In a substudy involving 634 participants, viral load was reduced by the end of treatment with nirmatrelvir–ritonavir. Serious adverse events with nirmatrelvir–ritonavir were reported in 9 participants in the PANORAMIC trial and in 4 participants in the CanTreatCOVID trial.

Conclusions

In two open-label trials, nirmatrelvir–ritonavir did not reduce the incidence of hospitalization or death among vaccinated higher-risk participants with SARS-CoV-2 infection. (Funded by the National Institute for Health and Care Research, and others; PANORAMIC ISRCTN number, 2021-005748-31; CanTreatCOVID ClinicalTrials.gov number, NCT05614349.)

Source: 

Link: https://www.nejm.org/doi/full/10.1056/NEJMoa2502457?query=TOC

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A newly emergent N1 #neuraminidase associated with clade 2.3.4.4b highly pathogenic avian #influenza #H5 viruses in North #America

 

Abstract

We investigated the evolutionary history of the newly emergent neuraminidase (am4N1) associated with the D1.1 and D1.2 genotypes of highly pathogenic avian influenza A(H5N1) viruses in North America. Phylogenetic inference places am4N1 in a sister clade to Eurasian avian, swine, and human A(H1N1)pdm09 viruses and distinct from 1918, pre-2009 human seasonal, and classical swine A(H1N1) lineages. Am4N1 descends from diverse avian N1 genes endemic to the Americas. Phylodynamic analysis indicates a monophyletic am4N1 lineage with numerous introductions of viruses carrying the am4N1 gene likely originating from western Canada into the United States during emergence of the D1.1 and D1.2 genotypes. The lineage has diversified and accumulated deletions in the stalk domain. Despite amino acid divergence, structural modeling shows conserved neuraminidase architecture in the globular head. Given its distinct ancestry and amino acid sequence, further studies are needed to assess cross-reactivity of antibodies from prior human A(H1N1)pdm09 infections.

Competing Interest Statement

The authors have declared no competing interest.

Funding Statement

This study did not receive any external funding.

Source: 

Link: https://www.medrxiv.org/content/10.64898/2026.03.09.26347929v1

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Loss of α2,3-linked #sialoside in the receptor-binding site of a #H5N1 #influenza hemagglutinin identified in a #human patient

 

Abstract

In November 2024, an adolescent female in British Columbia was hospitalized presenting with severe symptoms including respiratory failure due to infection with a novel H5N1 subtype influenza strain (BC24). Using cryogenic electron microscopy (cryo-EM), we show here that the N169 α2,3-linked auto-glycan that is found in the sialic acid binding site of previously studied H5 hemagglutinin (HA) proteins is absent in purified BC24 HA protein, suggesting greatly reduced affinity for α2,3-linked sialosides. Glycan microarray analysis shows that the BC24 HA protein displays reduced or no binding not just to most α2,3-linked sialosides, but also to α2,6-linked sialosides. Full-length BC24 HA expressed in A549 lung alveolar carcinoma cells drives membrane fusion, albeit at significantly lower levels than previous H5 HA proteins, and post-infection sera from the patient display strong binding to BC24 HA and HA proteins from other influenza subtypes. The high virulence of the BC24 strain despite weak receptor binding reveals further complexity in the factors that result in severe disease caused by avian influenza.

Competing Interest Statement

The authors have declared no competing interest.

Funder Information Declared

Canada Biomedical Research Fund

Canada Excellence Research Chairs, https://ror.org/02tvrwm90

Source: 

Link: https://www.biorxiv.org/content/10.64898/2026.01.19.700419v1

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#Management of #critical illness in an #adolescent caused by highly pathogenic avian #influenza #H5N1 virus infection in #BC, #Canada

 

Summary

Highly pathogenic avian influenza A(H5N1) viruses have been circulating among wild birds and are enzootic in poultry in some areas of the world with spillover to a wide range of terrestrial and marine mammals. Since 1997, sporadic animal to human, primarily poultry to human, transmission of highly pathogenic avian influenza A(H5N1) viruses has been reported in 25 countries. More recently there have been locally acquired infections in the Americas due to the 2.3.4.4b clade of the virus. Most of the recently detected human infections in the USA have been relatively mild but there have been cases of critical illness reported in several countries. In this Grand Round we present the first locally acquired highly pathogenic avian influenza A(H5N1) virus infection in Canada, which was in a 13-year-old female, who developed severe disease requiring prolonged critical care. She was infected with a clade 2.3.4.4b, genotype D1.1 virus and developed evidence of cytokine storm and received several modalities of care including combination antiviral therapy, renal replacement therapy, therapeutic plasma exchange, and invasive mechanical ventilation support with veno-venous extracorporeal life support. She recovered and was discharged home without requirement for additional support. This Grand Round describes important clinical and management considerations for critically ill patients infected with highly pathogenic avian influenza A(H5N1) virus.

Source: Lancet Infectious Diseases, https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(25)00773-X/abstract?rss=yes

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#Macrolide #Resistance and P1 Cytadhesin Genotyping of #Mycoplasma pneumoniae during #Outbreak, #Canada, 2024–2025

 

Abstract

We investigated macrolide resistance and P1 genotypes of Mycoplasma pneumoniae during the 2024–2025 outbreak in Hamilton, Ontario, Canada. Macrolide resistance remained stable at ≈10%–20%, but significant shifts in P1 genotype distribution and resistance rates in P1 types occurred, indicating notable changes in M. pneumoniae molecular epidemiology in Ontario since 2011–2012.

Source: 

Link: https://wwwnc.cdc.gov/eid/article/31/12/25-0872_article

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#Zoonotic and #Avian #Pathogen Detections in Fecal and Sediment #Samples - A Low-risk, High-throughput One Health Approach to #Surveillance

 

Abstract

Many pathogens, both those with human spillover potential as well as avian-specific viruses, are maintained in wild bird populations. While much surveillance for influenza A viruses (IAVs) is performed annually, surveillance for other pathogens is limited. Sampling of wild birds is often time-consuming, labour-intensive, involves physically handling wild birds, often limited in sample size, and involves handling of potentially infected birds, posing an increased risk of direct exposure for personnel. Given this, additional methods for surveillance are needed. Longitudinal, bi-weekly fecal and sediment sampling was performed at various sites in southern Manitoba, Canada, particularly focused in Winnipeg from May - October 2025. Sites were chosen based on the suitability of the area for waterfowl habitat, the presence of waterfowl in the area, as well as sites in proximity to reported outbreaks of H5N1 influenza virus. Fecal and sediment samples were collected and screened for the presence of influenza A virus (IAV), Newcastle disease virus (NDV), avian reovirus (ARV), and avian poxvirus (APXV). In total, 782 combined fecal and sediment samples were collected. Of the 714 fecal samples, 34 tested positive for IAV (4.8% prevalence). None of the IAV-positive fecal samples tested positive for H5 RNA. Of the 68 sediments tested, 15 tested positive for IAV (22.1% prevalence), four of which further tested positive for H5 RNA. NDV positivity was low, with only four positive fecal samples (0.56% prevalence) that were all collected on the same day. ARV positivity was also low, with five positive sediment samples (7.4% prevalence in sediment samples). Of the 782 total samples collected, of 559 samples that have been tested for APXV to date, all have tested negative. This work expands upon previous work showing the utility of environmental sampling for a variety of avian and zoonotic pathogens using a One Health approach that is both high-throughput and low-risk.

Competing Interest Statement

The authors have declared no competing interest.

Funder Information Declared

Canadian Institutes of Health Research, Tier 2 Canada Research Chair, 950 231498

Natural Sciences and Engineering Research Council, RGPIN-2018-06036

Source: 

Link: https://www.biorxiv.org/content/10.64898/2025.12.19.694637v1

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Serological #Evidence of Highly Pathogenic Avian #Influenza #H5N1 in Invasive Wild #Pigs in Western #Canada

 

Abstract

Influenza A virus (IAV) can infect a wide range of hosts, including wild and domestic pigs. Swine play an important role in influenza evolution and epidemiology due to their ability to get infected with both avian and human influenza viruses, potentially leading to reassorted virus variants. Interactions at the wild-domestic swine interface have been documented on multiple occasions, raising concern about pathogen transmission and the emergence of novel influenza strains. This study investigates the occurrence and subtypes of IAV infecting invasive wild pigs in Alberta, Canada. A total of 267 wild pigs were captured between 2021–2024. Exposure to IAV was initially detected by cELISA, with further confirmation of exposure to the H5Nx virus by hemagglutination inhibition (HI) and virus neutralization (VN) assays. Although no IAV genetic material was detected by qPCR, the seropositive samples by cELISA (4.17%; 5/120) coincided with the 2022–2024 highly pathogenic avian influenza virus (HPAI) H5N1 epizootic in Alberta, which involved outbreaks in wild species and domestic birds. These findings, combined with the epidemiological context, suggest interspecies transmission of HPAI H5N1 clade 2.3.4.4b to wild pigs. These results highlight the potential role of wild pigs as a new host in Canada and emphasize the need for continued surveillance of IAV in wild pig populations to assess the risk of spillover events at the wildlife, livestock, and human interfaces.

Source: 

Link: https://onlinelibrary.wiley.com/doi/10.1155/tbed/2720469

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Cross-reactive #neuraminidase inhibition #antibodies against #H5N1 by consecutive #influenza A imprinting cohorts of the past century: population-based serosurvey, British Columbia, #Canada

 

Abstract

Background: 

Avian influenza of the H5N1 subtype shares substantial relatedness in its neuraminidase (NA) surface protein with human influenza A H1N1 viruses of the past century. Understanding variation in pre-existing anti-N1 antibodies against H5N1 is critical to pandemic risk assessment and preparedness. 

Methods: 

We used anonymized, residual sera collected equally from ten age groups spanning one to >80 years during an August 2024 cross-sectional serosurvey in British Columbia, Canada. We assessed NA inhibition antibody titres by enzyme-linked lectin assay against H5N1 (N=575), H1N1pdm09 (N=250) and H3N2 (N=205). We compared anti-NA titres by birth (imprinting) cohorts defined in relation to historic N1 and/or N2 exposure opportunities. 

Results: 

Among participants with median age 32 (IQR: 15-62) years, 404 (70%) had cross-reactive anti-N1 titre ≥10 against H5N1, with 260 (45%), 182 (32%) and 98 (17%), having titres ≥40, ≥80 and ≥160, respectively. H5N1 titres were consistently lower but strongly associated with H1N1pdm09 (r=0.86; 95%CI:0.82-0.89). Geometric mean titres against H1N1pdm09 and H5N1 peaked among young adults born 1997-2003 (427.9, 100.8), declining to lows among young children born 2015-2023 (20.7, 6.8) and middle-aged adults born 1957-1967 (25.1, 10.7), increasing to similar secondary peak among older adults born pre-1947 (387.3, 81.0). 

Conclusions: 

A substantial proportion of the population has pre-existing, cross-reactive anti-N1 antibodies against H5N1. We interpret variation by age and imprinting cohorts within a unifying hypothesis, emphasizing the role of historic influenza pandemics in expanding and refining the immune repertoire through heightened attack rates and shifts in immunological hierarchies. Our findings have implications for H5N1 and other zoonotic influenza risk assessment.

Competing Interest Statement

DMS is Principal Investigator on grants received to her institution from the Public Health Agency of Canada, Pacific Public Health Foundation, Canadian Institutes of Health Research and the Michael Smith Foundation for Health Research for unrelated work. As the Provincial Health Officer with authority under the emergency provisions of the Public Health Act, BH authorized the provision and analysis of the anonymized sera used in this study; the study was separately reviewed and approved by the UBC Clinical Research Ethics Board and Health Canada-Public Health Agency of Canada Research Ethics Board. No other competing interests were declared.

Funding Statement

This work was supported by the Public Health Agency of Canada (Grant number: 2021-HQ-00067), received by the Institution of DMS. The views expressed herein do not necessarily represent the views of the Public Health Agency of Canada.

Source: MedRxIV, https://www.medrxiv.org/content/10.1101/2025.09.19.25336209v1

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Intensive #transmission in wild, migratory #birds drove rapid geographic #dissemination and repeated #spillovers of #H5N1 into agriculture in North #America

Abstract

Since late 2021, a panzootic of highly pathogenic H5N1 avian influenza virus has driven significant morbidity and mortality in wild birds, domestic poultry, and mammals. In North America, infections in novel avian and mammalian species suggest the potential for changing ecology and establishment of new animal reservoirs. Outbreaks among domestic birds have persisted despite aggressive culling, necessitating a re-examination of how these outbreaks were sparked and maintained. To recover how these viruses were introduced and disseminated in North America, we analyzed 1,818 Hemagglutinin (HA) gene sequences sampled from North American wild birds, domestic birds and mammals from November 2021-September 2023 using Bayesian phylodynamic approaches. Using HA, we infer that the North American panzootic was driven by ~8 independent introductions into North America via the Atlantic and Pacific Flyways, followed by rapid dissemination westward via wild, migratory birds. Transmission was primarily driven by Anseriformes, shorebirds, and Galliformes, while species such as songbirds, raptors, and owls mostly acted as dead-end hosts. Unlike the epizootic of 2015, outbreaks in domestic birds were driven by ~46-113 independent introductions from wild birds, with some onward transmission. Backyard birds were infected ~10 days earlier on average than birds in commercial poultry production settings, suggesting that they could act as early warning signals for transmission upticks in a given area. Our findings support wild birds as an emerging reservoir for HPAI transmission in North America and suggest continuous surveillance of wild Anseriformes and shorebirds as crucial for outbreak inference. Future prevention of agricultural outbreaks may require investment in strategies that reduce transmission at the wild bird/agriculture interface, and investigation of backyard birds as putative early warning signs.

Competing Interest Statement

The authors have declared no competing interest.

Source: BioRxIV, https://www.biorxiv.org/content/10.1101/2024.12.16.628739v2

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A #Genome #Sequence Variant #Monitoring Program for Seasonal #Influenza #H3N2 & #RSV using #Wastewater-Based #Surveillance in #Ontario, Canada

Abstract

Seasonal respiratory viruses, such as the Influenza A virus and the respiratory syncytial virus, are responsible for over a billion infections worldwide each year resulting in a substantial burden on health care systems. Surveillance of these viruses, including their prevalence in communities and their evolution, are essential for informing public health decisions and recommending vaccine formulations and schedules. Typically, these viruses are monitored using clinical samples from patients seeking medical attention. Recently, wastewater-based surveillance (WBS) has been leveraged to understand transmission dynamics and genome evolution of SARS-CoV-2 and seasonal respiratory viruses. To further the utility of WBS we developed and implemented novel tiled-amplicon sequencing assays to identify and track Influenza A virus H3N2 and respiratory syncytial virus A circulating in Southern Ontario, Canada. We also developed virus specific deconvolution tools to estimate the abundance of mixed lineages in wastewater. These assays were able to accurately determine which lineages were circulating in wastewater with high sensitivity and specificity. If implemented in regular surveillance programs, they could be used to inform real-time public health decisions and determine potential disease surge with impact on emergency room visits and hospitalization, as well as track which emerging strains will become predominant in the future and determine which strains should be the focus of seasonal vaccines.

Competing Interest Statement

The authors have declared no competing interest.

Funder Information Declared

Integrated Network for the Surveillance of Pathogens (INSPIRE), CBRF2-2023-00008

Ministry of the Environment, Conservation and Parks, https://ror.org/01q2d8e83, 2021-02-1-1564736554

Source: BioRxIV, https://www.biorxiv.org/content/10.1101/2025.07.29.667219v1

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Spatiotemporal #reconstruction of the North #American #H5N1 #outbreak reveals successive #lineage #replacements by descendant reassortants

Abstract

The November 2021 introduction of highly pathogenic avian influenza A(H5N1) clade 2.3.4.4b into North America triggered a devastating outbreak, affecting more than 180 million domestic birds and spreading to more than 80 wildlife species across Canada and the US. From this outbreak, we have sequenced 2955 complete A(H5N1) viral genomes from samples collected in Canada and, in conjunction with previously published data, performed multifaceted phylodynamic analyses. These analyses reveal extensive diversification of A(H5N1) viruses via reassortment with low-pathogenic avian influenza viruses. We find evidence of repeated ancestral strain replacement by direct descendants, indicative of compounding viral fitness increases. Spatiotemporal modeling identified critical geographic areas facilitating transcontinental spread and demonstrated genotype-specific host dynamics, offering essential data for ongoing control and prevention strategies.

Source: Science Advances, https://www.science.org/doi/10.1126/sciadv.adu4909

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Highly Pathogenic Avian #Influenza A(#H5N1) in Wild #Birds and a #Human, British Columbia, #Canada, 2024

Abstract

We characterized highly pathogenic avian influenza A(H5N1) clade 2.3.4.4b genotype D1.1 in wild birds and a human in British Columbia, Canada, during 2024. D1.1, the predominant genotype circulating in fall 2024, is a reassortment between Eurasian A3 lineage viruses, introduced to North America in 2022, and North American lineage viruses.

Source: US Centers for Disease Control and Prevention, https://wwwnc.cdc.gov/eid/article/31/6/24-1862_article

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#Measles – Region of the #Americas (#WHO D.O.N., April 28 '25)

{Excerpt}

Situation at a glance

As of 18 April 2025, a total of 2318 measles cases, including three deaths, have been confirmed in six countries in the WHO Region of the Americas, an 11-fold increase compared to the same period in 2024. 

The majority of cases have occurred among people between 1 to 29 years, who are either unvaccinated or have an unknown vaccination status. 

Additionally, most cases are imported or linked to importation. 

Measles is a highly contagious, airborne viral disease that can lead to severe complications and death. 

Although it is preventable with two doses of the vaccine, over 22 million children worldwide did not receive their first dose of the vaccine in 2023. This has contributed to a global rise in measles cases in 2024, which heightens the risk of imported infections, particularly from unvaccinated travellers arriving from areas where the virus is actively circulating. 

WHO is working closely with countries in the WHO Region of the Americas to prevent the spread and reintroduction of measles. 

The regional risk is currently assessed as high, while the global risk remains moderate.

Description of the situation

From 1 January to 18 April 2025, a total of 2318 measles cases, including three deaths, were confirmed in the WHO Region of the Americas, an 11-fold increase compared to the 205 cases of measles reported in the same period in 2024. 

The cases have been reported from six countries: 

- Argentina (n= 21 cases), 

- Belize (n= 2 cases), 

- Brazil (n= 5 cases), 

- Canada (n=1069 cases), 

- Mexico (n= 421 cases including one death), and 

- the United States of America (n=800 cases, including two deaths).

(...)

Source: World Health Organization, https://www.who.int/emergencies/disease-outbreak-news/item/2025-DON565

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#Neuraminidase #reassortment and #oseltamivir #resistance in clade 2.3.4.4b A(#H5N1) viruses circulating among #Canadian #poultry, 2024

Abstract

We report the detection of a clade 2.3.4.4b A(H5N1) reassortant virus with a neuraminidase surface protein derived from a North American lineage low-pathogenic avian influenza virus. This virus caused a widespread and ongoing outbreak across 45 poultry farms in British Columbia, Canada. Isolates from 8 farms reveal a mutation in the neuraminidase protein (H275Y) that is exceptionally rare among clade 2.3.4.4b viruses (present in 0.045% of publicly available clade 2.3.4.4b isolates). NA-H275Y is a well-known marker of resistance to the neuraminidase inhibitor oseltamivir. We demonstrate that this substitution maintains its resistance phenotype on the genetic background of H5N1 clade 2.3.4.4b viruses.

Source: Emerging Microbes and Infections, https://www.tandfonline.com/doi/full/10.1080/22221751.2025.2469643

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#Canada - High pathogenicity avian #influenza #H5N5 viruses (#poultry) (Inf. with) - Immediate notification

On January 24, 2025, the Canadian Food Inspection Agency (CFIA) was notified of mortality in a non-commercial backyard layer poultry farm in Newfoundland and Labrador. The CFIA National Centre for Foreign Animal Disease has confirmed on February 12, 2025 that the virus was H5N5. The HA of the H5 virus from the samples belongs to Eurasian Gs/GD lineage HPAI H5N1 (2.3.4.4b) with cleavage site motif of “PLREKRRKR/GLF”, compatible with HPAI viruses. The sample contained AI virus similar to European like - H5N5 (2023) viruses which came to Canada via the Atlantic flyway. The viruses contained wholly Eurasian H5N5 genome segments. The CFIA has immediately quarantined the IP and is implementing strict movement controls and a stamping out policy. Primary control zone (PCZ) has been put in place around the IP. Surveillance is ongoing in the affected areas. WOAH data on poultry and non-poultry can be visualized and extracted on the AI dashboard in domestic birds available at https://cahss.ca/cahss-networks/poultry-new (select poultry categories to show data related to HPAI poultry events 4294, 5229, 6003, and 6267). Wildlife surveillance as well as the Canadian Notifiable Avian Influenza Surveillance System (CanNAISS) activities for poultry are ongoing in Canada.

Source: WOAH, https://wahis.woah.org/#/in-review/6267

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