#Host type governs #influenza evolutionary #strategy across reservoir and #spillover hosts

 

Abstract

Despite its high propensity for host switching, the evolutionary mechanisms underlying influenza host adaptation remain unclear. H3Nx influenza viruses are uniquely generalist, with long-term lineages that circulate in avian, human, swine, equine, and canine hosts. Using 13,295 H3Nx sequences, we quantified host-specific adaptive evolution and developed a pipeline to map reassortment events onto trees with measures of statistical uncertainty. We find that while H3Nx viruses in mammals undergo adaptive evolution in HA and NA, viruses in birds experience very little directional selection. Instead, avian lineages exhibit high rates of reassortment, frequently generating novel reassortant lineages that persist transiently and turn over rapidly. 29.8-47.4% of all avian reassortant lineages are purged within the first year of circulation, and reassortment shows no fitness benefit in birds. In contrast, reassorted lineages in swine are more likely to persist long-term, suggesting that reassortment in swine may be broadly beneficial. Segment-specific reassortment patterns were also distinct between avian and mammalian viruses, with NA reassorting more frequently than expected in birds, but less frequently than expected in swine. Reassortment events are enriched between mammalian, but not avian, host switches, suggesting that reassortment may be most beneficial for mediating host switches among mammalian species. Together, our data suggest that host differences drive fundamentally different evolutionary outcomes for influenza viruses, transitioning from reassortment-dominant evolution in their avian reservoir, to varying degrees of adaptation upon establishment in mammals.

Competing Interest Statement

The authors have declared no competing interest.

Funder Information Declared

Pew Charitable Trusts

Margaret Q. Landenberger Research Foundation

National Institute of Allergy and Infectious Diseases

National Institutes of Health

Department of Health and Human Services

United States Department of Agriculture

Agricultural Research Service

Source: 

Link: https://www.biorxiv.org/content/10.64898/2026.09.15.751820v1

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#Influenza at #human - #animal #interface - #Summary & #risk assessment, 8 Aug. - 6 Sept. '26 (WHO): 1 #H5N1 case in #Bangladesh, 3 #H9N2 cases in #China, 2 #H1N2v cases in #US

 

Influenza at the human-animal interface Summary and risk assessment, from 8 August to 6 September 2026 {1}

    • New human cases {2}: 

        ° From 8 August to 6 September 2026, based on reporting date,  detections of influenza A(H5N1) in one human and influenza A(H9N2) in  three humans were officially reported. Additionally, two human cases of infection with influenza A(H1N2) variant (A(H1N2)v) viruses were detected.

    • Circulation of influenza viruses with zoonotic potential in animals: 

        ° High pathogenicity avian influenza (HPAI) events in poultry and  non-poultry animal species continue to be reported to the World Organisation for  Animal Health (WOAH).{3} The Food and Agriculture Organization of the United  Nations (FAO) also provides a global update on avian influenza viruses with  pandemic potential.{4} Additionally, low pathogenicity avian influenza viruses as  well as swine influenza viruses continue to circulate in animal populations.

    • Risk assessment {5}: 

        ° There have been no reports of sustained human-to-human transmission associated with the above-mentioned human infection events.  Based on information available at the time of this update, the overall public health  risk from currently known influenza A viruses detected at the  human-animal interface has not changed and, at present, these viruses are  not thought to be capable of sustained human-to-human transmission, although  this could change as they evolve. Whilst human infections with viruses of animal  origin are infrequent, they are not unexpected at the human-animal interface.

    • IHR compliance {6}: 

        ° This includes any influenza A virus that has demonstrated the  capacity to infect a human, and its haemagglutinin (HA) gene (or protein) is not a  mutated form of those, i.e. A(H1) or A(H3), circulating widely in the human  population. Information from these notifications is critical to inform risk  assessments for influenza at the human-animal interface.

Avian influenza viruses in humans

A(H5N1), Bangladesh

    On 30 August, Bangladesh, through the national IHR focal point, notified WHO of one laboratory-confirmed human infection with an A(H5) virus in a  child from Rangpur division. 

    On 15 August 2026, the child developed a fever, cough and rhinitis and was  admitted to hospital on 17 August. 

    On 18 August, a nasopharyngeal swab and throat swab was collected as  part of hospital-based influenza surveillance and tested positive for influenza A(H5) by real-time RT-PCR at the icddr,b laboratory on the same day. 

    The sample was subsequently confirmed positive for influenza A(H5N1)  at the Molecular and Genomic Laboratory Department of Institute of Epidemiology,  Disease Control and Research (IEDCR) and National Influenza  Centre (NIC) of Bangladesh. 

    Genetic sequencing is underway. 

    The child remained hospitalized and was improving clinically at the time  of reporting.

    There was no reported history of travel outside the area of residence. The  child had a history of exposure to duck and chickens, including some that  were sick, in the household and adjacent households. 

    Poultry meat and oropharyngeal swab specimens collected from several  backyard chickens on 26 August tested negative for influenza A(H5).

    Close contacts were identified and placed under monitoring and all  contacts remained asymptomatic during the observation period, except for two heath care workers. 

    Respiratory specimens collected from these two individuals tested negative for influenza A viruses.

    This is the 4th laboratory-confirmed human case of avian influenza A(H5)  reported in Bangladesh in 2026.

    According to reports received by WOAH, various influenza A(H5) subtypes  continue to be detected in wild and domestic birds in Africa, the Americas, Asia,  Europe and Oceania. Infections in non-human mammals are also reported,  including in marine and land mammals.{7} A list of bird and mammalian species  affected by HPAI A(H5) viruses is maintained by FAO.{8}

Risk assessment for avian influenza A(H5N1) viruses:

    1. What is the current global public health risk of additional human cases of  infection with avian influenza A(H5N1) viruses?

        ° Most human infections so far have been reported in people exposed  to A(H5N1) viruses, for example, through contact with infected poultry or  contaminated environments, including live poultry markets, and occasionally  infected mammals and contaminated environments. As long as the viruses  continue to be detected in animals and related environments humans are exposed  to, further human cases associated with such exposures are expected  but remain unusual. The impact for public health if additional sporadic cases are detected is minimal. The current overall global public health risk is low.

    2. What is the likelihood of sustained human-to-human transmission of avian  influenza A(H5N1) viruses related to the events above?

        ° No sustained human-to-human transmission has been identified  associated with the recent reported human infections with avian  influenza A(H5N1) viruses. There has been no reported human-to-human transmission of A(H5N1) viruses since 2007, although there may be gaps in  investigations. In 2007 and the years prior, small clusters of A(H5N1) virus  infections in humans were reported, including some involving health care workers,  where limited human-to-human transmission could not be excluded;  however, sustained human-to-human transmission was not reported.  Current evidence suggests that influenza A(H5N1) viruses related to these events did not acquire the ability to efficiently transmit between people.

      3. What is the likelihood of international spread of avian influenza A(H5N1) viruses by travellers?

        ° Should infected individuals from affected areas travel internationally, their infection may be detected in another country during travel  or after arrival. If this were to occur, further community- level spread is  considered unlikely as current evidence suggests these viruses have  not acquired the ability to transmit easily among humans.  

A(H9N2), China

    Between 13 August and 1 September 2026, China notified WHO of three laboratory-confirmed human cases of A(H9N2) virus infection. 

(...)

    All cases had direct or indirect exposure to poultry and/or local live bird  markets. Samples from environments associated with the likely area of exposure  of some of the cases tested positive for A(H9) viruses. 

    No further cases were detected among contacts of these cases.

Risk assessment for avian influenza A(H9N2):

    1. What is the global public health risk of additional human cases of infection  with avian influenza A(H9N2) viruses?

        ° Most human cases follow exposure to the A(H9N2) virus through  contact with infected poultry or contaminated environments. Most human  infections of A(H9N2) to date have resulted in mild clinical illness. Since the  virus is endemic in poultry in multiple countries in Africa and Asia, additional human cases associated with exposure to infected poultry or  contaminated environments are expected but remain unusual. The impact to  public health if additional sporadic cases are detected is minimal. The  overall global public health risk is low.

    2. What is the likelihood of sustained human-to-human transmission of avian  influenza A(H9N2) viruses related to these events?

        ° At the present time, no sustained human-to-human transmission  has been identified associated with the recently reported human  infections with A(H9N2) viruses. Current evidence suggests that A(H9N2) viruses  from these cases did not acquire the ability of sustained transmission among humans.

    3. What is the likelihood of international spread of avian influenza A(H9N2)  virus by travellers?

        ° Should infected individuals from affected areas travel internationally, their infection may be detected in another country during travel  or after arrival. If this were to occur, further community level spread is considered  unlikely as current evidence suggests the A(H9N2) virus subtype has not acquired the ability to transmit easily among humans.

Swine influenza viruses in humans

Influenza A(H1N2)v, United States of America

    Since the risk assessment of 8 August 2026, two human infections with influenza A(H1N2v) viruses were detected in the state of Michigan.{7} 

    The patients, both <18 years of age, developed illness in the week of 15  August. They were not hospitalized and have recovered. Both attended the same agricultural fair where sick swine were present. The cases did not have  contact with each other and  no additional human infections with A(H1N2)v  viruses have been detected around this event. 

    Including these two cases, there have been a total of three human  infections with variant influenza A viruses reported in the United States in 2026.

Risk Assessment:

    1. What is the public health risk of additional human cases of infection with  swine influenza viruses?

        ° Swine influenza viruses circulate in swine populations in many  regions of the world. Depending on geographic location, the genetic characteristics  of these viruses differ. Most human cases are exposed to swine  influenza viruses through contact with infected animals or contaminated environments. Human infection tends to result in mild clinical illness  in most cases. Since these viruses continue to be detected in swine  populations, further human cases are expected but remain unusual. The impact  for public health if additional cases are detected is minimal. The overall risk of additional human cases is low.

    2. What is the likelihood of sustained human-to-human transmission of swine influenza viruses? 

        ° No sustained human-to-human transmission was identified  associated with the event described above. Current evidence suggests  that contemporary swine influenza viruses have not acquired the ability  of sustained transmission among humans, therefore sustained human-to-human  transmission is thus currently considered unlikely.

    3. What is the likelihood of international spread of swine influenza viruses by travelers? 

        ° Should infected individuals from affected areas travel internationally, their infection may be detected in another country during travel  or after arrival. If this were to occur, further community level spread is considered  unlikely as current evidence suggest that these viruses have not acquired the ability to transmit easily among humans.

Overall risk management recommendations:

Surveillance and investigations

    • Due to the constantly evolving nature of influenza viruses, WHO  continues to stress the importance of global strategic surveillance in animals and  humans to detect virologic, epidemiologic and clinical changes associated with  circulating influenza viruses that may affect human (or animal) health. Continued  vigilance is needed within affected and neighbouring areas to detect infections in  animals and humans. Close collaboration with the animal health and environment  sectors is essential to understand the extent of the risk of human exposure and to prevent and control the spread of animal influenza. WHO has published  guidance on surveillance for human infections with avian influenza A(H5) viruses.

    • Epidemiologic and virologic surveillance and the follow-up of suspected  human cases should continue systematically. Guidance on investigation of non- seasonal influenza and other emerging acute respiratory diseases has been  published on the WHO website.

    • Countries should increase avian influenza surveillance in domestic  and wild birds, enhance surveillance for early detection in cattle  populations in countries where HPAI is known to be circulating, include HPAI as a  differential diagnosis in non-avian species, including cattle and other livestock  populations, with high risk of exposure to HPAI viruses; monitor and investigate cases in non-avian species, including livestock, report cases of HPAI in  all animal species, including unusual hosts, to WOAH and other international  organizations, share genetic sequences of avian influenza viruses in publicly  available databases, implement preventive and early response measures to break  the HPAI transmission cycle among animals through movement restrictions of  infected livestock holdings and strict biosecurity measures in all holdings, employ  good production and hygiene practices when handing animal products, and protect  persons in contact with suspected/infected animals.{8} More  guidance can be found from WOAH and FAO.

    • When there has been human exposure to a known outbreak of an  influenza A virus in domestic poultry, wild birds or other animals – or when there  has been an identified human case of infection with such a virus – enhanced  surveillance in potentially exposed human populations becomes necessary.  Enhanced surveillance should consider the health care seeking behaviour of the  population, and could include a range of active and passive health care and/or  communitybased approaches, including: enhanced surveillance in local influenza- like illness (ILI)/SARI systems, active screening in hospitals and of groups that  may be at higher occupational risk of exposure, and inclusion of other sources  such as traditional healers, private practitioners and private diagnostic laboratories.

    • Vigilance for the emergence of novel influenza viruses with pandemic  potential must be maintained at all times, including during a non-influenza  emergency. To maximize the value of influenza surveillance platform for other  respiratory threats, WHO has updated and published practical guidance for integrated surveillance.

Notifying WHO

    • All human infections caused by a new subtype of influenza virus are  notifiable under the International Health Regulations (IHR, 2005).{9,10} State  Parties to the IHR (2005) are required to immediately notify WHO of any  laboratory-confirmed {11} case of a recent human infection caused by an influenza A virus with the potential to cause a pandemic {12}. Evidence of illness  is not required for this report. Evidence of illness is not required for this report.

    • WHO published the case definition for human infections with avian  influenza A(H5) virus requiring notification under IHR (2005):  https://www.who.int/teams/global-influenzaprogramme/avian-influenza/case-definitions.

Virus sharing and risk assessment

    • It is critical that these influenza viruses from animals or from humans are  fully characterized in appropriate animal or human health influenza reference  laboratories. Under WHO’s Pandemic Influenza Preparedness (PIP) Framework,  Member States are expected to share influenza viruses with pandemic potential on a timely basis {13} with a WHO Collaborating Centre for influenza of GISRS. The  viruses are used by the public health laboratories to assess the risk of pandemic influenza and to develop candidate vaccine viruses.

    • The Tool for Influenza Pandemic Risk Assessment (TIPRA) provides an  in-depth assessment of risk associated with some zoonotic influenza viruses –  notably the likelihood of the virus gaining human-to-human transmissibility, and  the impact should the virus gain such transmissibility. TIPRA maps relative risk  amongst viruses assessed using multiple risk elements. The results of  TIPRA  complement those of the risk assessment provided here, and those of prior TIPRA  risk assessments are published at http://www.who.int/teams/global-influenza-programme/avianinfluenza/tool-for-influenza-pandemic-risk-assessment-(tipra).

Risk reduction

    • Given the observed extent and frequency of avian influenza in poultry, wild birds and some wild and domestic mammals, the public should  avoid contact with animals that are sick or dead from unknown causes, including  wild animals, and should report dead birds and mammals or request their removal by contacting local wildlife or veterinary authorities.

    • Eggs, poultry meat and other poultry food products should be properly  cooked and properly handled during food preparation. Due to the potential health  risks to consumers, raw milk should be avoided. WHO advises consuming  pasteurized milk. If pasteurized milk isn’t available, heating raw milk until it boils makes it safer for consumption.

    • WHO has published practical interim guidance to reduce the risk of  infection in people exposed to avian influenza viruses.

Trade and travellers

    • WHO advises that travellers to countries with known outbreaks of  animal influenza should avoid farms, contact with animals in live animal markets,  entering areas where animals may be slaughtered, or contact with any surfaces  that appear to be contaminated with animal excreta. Travelers should also wash  their hands often with soap and water. All individuals should follow good food safety and hygiene practices.

    • WHO does not advise special traveller screening at points of entry or  restrictions with regards to the current situation of influenza viruses at the  human-animal interface. For recommendations on safe trade in animals and  related products from countries affected by these influenza viruses, refer to WOAH guidance.

Links:

    ° WHO Human-Animal Interface web page https://www.who.int/teams/global-influenza-programme/avian-influenza

    ° WHO Influenza (Avian and other zoonotic) fact sheet https://www.who.int/news-room/fact-sheets/detail/influenza-(avian-and-other-zoonotic)

    ° WHO Protocol to investigate non-seasonal influenza and other emerging acute respiratory diseases https://www.who.int/publications/i/item/WHO-WHE-IHM-GIP-2018.2

    ° WHO Public health resource pack for countries experiencing outbreaks of  influenza in animals: https://www.who.int/publications/i/item/9789240076884

    ° Cumulative Number of Confirmed Human Cases of Avian Influenza A(H5N1) Reported to WHO https://www.who.int/teams/global-influenza-programme/avian-influenza/avian-a-h5n1-virus

    ° Avian Influenza A(H7N9) Information https://www.who.int/teams/global-influenza-programme/avian-influenza/avian-influenza-a-(h7n9)-virus

    ° World Organisation of Animal Health (WOAH) web page: Avian Influenza https://www.woah.org/en/home/

    ° Food and Agriculture Organization of the United Nations (FAO) webpage:  Avian Influenza https://www.fao.org/animal-health/avian-flu-qa/en/

    ° WOAH/FAO Network of Expertise on Animal Influenza (OFFLU) http://www.offlu.org/

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{1} This summary and assessment covers information confirmed during this  period and may include information received outside of this period.

{2} For epidemiological and virological features of human infections with animal  influenza viruses not reported in this assessment, see the reports on human cases  of influenza at the human-animal interface published in the Weekly Epidemiological Record here.

{3} Avian influenza. Global situation. World Organisation for Animal Health  (WOAH) (https://www.woah.org/en/disease/avian-influenza/#ui-id-2).

{4} Global Avian Influenza Viruses with Zoonotic Potential situation update. Food  and Agriculture Organization of the United Nations (FAO)  (https://www.fao.org/animal-health/situation-updates/global-aiv-with-zoonoticpotential).

{5} Rapid risk assessment of acute public health events. World Health  Organization; 2012 (https://iris.who.int/handle/10665/70810).

{6} Case definitions for the four diseases requiring notification in all  circumstances under the International Health Regulations (2005). World Health Organization; 2009 (https://www.who.int/publications/m/item/casedefinitions-for-the-four-diseases-requiring-notification-to-who-in-all-circumstances-under-the-ihr-(2005)).

{7} Weekly US Influenza Surveillance Report: Key Updates for Week 32, ending  August 15, 2026. US Centers for Disease Control and Prevention; 2026  (https://www.cdc.gov/fluview/surveillance/2026-week-32.html).

{8} World Organisation for Animal Health. Statement on High Pathogenicity Avian  Influenza in Cattle, 6 December 2024 (https://www.woah.org/en/high-pathogenicity-avian-influenza-hpai-in-cattle/).

{9} World Health Organization. International Health Regulations (2005), as  amended through resolutions WHA67.13 (2014), WHA75.12 (2022), and  WHA77.17 (2024) (https://apps.who.int/gb/bd/pdf_files/IHR_2014-2022-2024-en.pdf).

{10} World Health Organization. Case definitions for the four diseases requiring  notification in all circumstances under the International Health Regulations (2005)  (https://www.who.int/publications/m/item/casedefinitions-for-the-four-diseases-requiring-notification-to-who-in-all-circumstances-under-the-ihr-(2005)).

{11} World Health Organization. Manual for the laboratory diagnosis and  virological surveillance of influenza (2011) (https://apps.who.int/iris/handle/10665/44518).

{12} World Health Organization. Pandemic influenza preparedness framework for  the sharing of influenza viruses and access to vaccines and other benefits, 2nd  edition (https://iris.who.int/handle/10665/341850).

{13} World Health Organization. Operational guidance on sharing influenza  viruses with human pandemic potential (IVPP) under the Pandemic Influenza  Preparedness (PIP) Framework (2017) (https://apps.who.int/iris/handle/10665/259402).

Source: 

Link: https://www.who.int/publications/m/item/influenza-at-the-human-animal-interface-summary-and-assessment--6-september-2026

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#USA, Two #human #infections with #influenza #H1N2v virus were reported by the #Michigan (US CDC, August 21 '26)

 

{Excerpt}

(...)

Novel Influenza A Virus Infections

    Two human infections with influenza A(H1N2) variant (A(H1N2)v) virus were reported by the Michigan Department of Health and Human Services.

    The patients, who are <18 years of age, initially developed illness and sought healthcare during the week ending August 15, 2026 (Week 32). 

    The patients were not hospitalized, one patient received influenza antiviral treatment, and both are recovering from their illnesses. 

    Investigation by local and state public health officials identified that both patients, who have not had contact with one another, had attended the same agricultural fair where ill swine were present prior to their illness onset. 

    No additional cases of human infection with A(H1N2)v virus associated with these cases or the fair have been identified.

    These are the third and fourth human infections with a variant influenza virus reported in the 2025-2026 season; all four have been influenza A(H1N2)v viruses.

    When an influenza virus that normally circulates in swine (but not people) is detected in a person, it is called a “variant” influenza virus. 

    Most human infections with variant influenza viruses occur following exposure to swine, but human-to-human transmission can occur. 

    It is important to note that in most cases, variant influenza viruses have not shown the ability to spread easily and sustainably from person to person.

(...)

Source: 

Link: https://www.cdc.gov/fluview/surveillance/2026-week-32.html

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The return of #H1N1: Reemergence of the #influenza virus A subtype H1N1 in 1977

 

Abstract

Four major influenza pandemics and two notable outbreaks have been recorded since 1900. This paper discusses the history of the 1977 influenza virus A H1N1 outbreak and re-emergence, often referred to as the “Russian flu” or the “red flu". We describe the likely events leading to the outbreak, including a brief history of the 1976 H1N1 outbreak in a military base in the United States. We reconstruct the spread of the H1N1 virus across the globe in 1977–1978 and discuss the epidemiology of the outbreak. We describe the likely origins of this unusual outbreak mainly affecting young people, including opinions and evidence pointing towards an unnatural origin. Finally, we outline the vaccines developed and vaccination campaigns that were carried out to combat the outbreak.

Source: 

Link: https://www.sciencedirect.com/science/article/pii/S0264410X26007723?via%3Dihub

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#USA, MDHHS confirms detection of #influenza A #H1N2 variant (#swine flu) in #Michigan resident (August 15 '26)

 

    LANSING, Mich. – The Michigan Department of Health and Human Services (MDHHS), Kent County Health Department (KCHD) and Ionia County Health Department have identified a human case of influenza A H1N2 variant (swine flu) in an Ionia County resident who was a swine exhibitor at the Kent County Youth Fair. 

    The fair took place Aug. 3-8 at the Grand Agricultural Center of West Michigan in Lowell.

    The individual tested presumptive positive at the MDHHS Bureau of Laboratories for swine flu and was confirmed by the Centers for Disease Control and Prevention (CDC) on Friday.

    MDHHS and KCHD have been reaching out to swine exhibitors and their families who visited the swine barns at the Kent County Youth Fair to identify any additional illnesses in those who may have been exposed to influenza from infected pigs. 

    KCHD has alerted providers in the area to watch for patients presenting with respiratory symptoms who report exposure to swine or visited the fair.

    “While the risk to the general public remains low, we want visitors who attended the Kent County Youth Fair to be alert to symptoms and take appropriate precautions,” said Dr. Natasha Bagdasarian, chief medical executive. 

    “Anyone who develops flu‑like symptoms after possible exposure should contact their health care provider and let them know about their recent contact with pigs at the fair. Individuals who are sick should stay home until they have fully recovered.”

    “It’s not unusual for flu viruses to occur in pigs, and while rare, those flu viruses can be transmitted to people by sick pigs,” said Dr. Nora Wineland, State Veterinarian, Michigan Department of Agriculture and Rural Development (MDARD). 

    “MDARD encourages exhibitors to follow disease prevention practices and work with their veterinarian if they suspect illness in an animal. It is still safe to enjoy your local fair, and visitors are encouraged to follow simple hygiene practices to help keep both people and animals healthy.”

    Pigs may be infected with swine influenza viruses that are different from human flu viruses. Swine flu viruses spread among pigs and – while rare – they can spread from pigs to people too. Spread of swine flu viruses from a pig to a person is thought to happen in the same way that human flu viruses spread; mainly through droplets when infected pigs cough and sneeze.

    MDHHS reiterates precautions the public can take to avoid potential exposure at farms, fairs and exhibits:

        ° Do not eat or drink in livestock barns or show rings.

        ° Do not take toys, pacifiers, cups, baby bottles, strollers or similar items into pig areas.

        ° Anyone who is at high risk of serious flu complications should avoid contact with pigs and swine barns when attending a fair.

        ° Get an annual influenza vaccination.

Below are some steps you can take to protect yourself and prevent the spread of any illness:

        ° Wash hands often with soap and water. If soap and water are not available, use an alcohol-based hand rub. 

        ° Avoid touching your eyes, nose and mouth. Germs spread this way. 

        ° Cover your nose and mouth with a tissue when you cough or sneeze. Throw the tissue in the trash after you use it. 

        ° Avoid close contact with sick people. If you are sick, stay home from work or school until your illness is over.

        ° Avoid contact with pigs if you have flu-like symptoms. Wait seven days after your illness started or until you have been without fever for 24 hours without the use of fever-reducing medications, whichever is longer. 

    Symptoms of variant influenza infection in people are similar to those of seasonal flu viruses and may include:

        ° Fever.

        ° Cough.  

        ° Runny nose.

        ° Body aches.

        ° Nausea.

        ° Vomiting.

        ° Diarrhea.

    Variant influenza infections, including influenza A H1N2 can sometimes cause severe disease, even in healthy people.

    Severe illness can include complications, such as pneumonia, which may require hospitalization, and in some cases can result in death.

    People who are at high risk of developing complications if they get variant influenza infection include:

        ° Children younger than five years of age.

        ° People 65 years of age and older.

        ° Pregnant people.

    People with certain long-term health conditions, such as asthma, diabetes, heart disease, weakened immune systems and neurological or neurodevelopmental conditions.

    The time period it takes from exposure to illness for variant influenza is similar to that of seasonal influenza, which can be up to 10 days, but is most commonly three days. 

    Currently, there is no human vaccine for swine flu and the seasonal flu vaccine will not protect against swine flu; however, prescription antiviral drugs, such as oseltamivir and zanamivir, are effective in treating swine flu in humans. 

    Early treatment works best and may be especially important for people with a high-risk condition.

    For more information, visit CDC.gov/Swine-Flu.

Source: 

Link: https://www.michigan.gov/mdhhs/inside-mdhhs/newsroom/2026/08/14/mdhhs-confirms-detection-of-influenza-a-h1n2-variant-in-michigan-resident

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Detection and characterization of #antiviral #resistant viruses during the #influenza season of 2024–25

 

ABSTRACT

During the high severity season of 2024–25, CDC with public health partners sequenced and analyzed genomes of >10,000 influenza viruses for antiviral resistance markers. Available sequence-flagged and representative viruses were tested with antivirals using in vitro assays. In the US, three oseltamivir-resistant A(H3N2) viruses had treatment-emergent neuraminidase (NA) mutations, either E119V or R292K. Oseltamivir-resistant A(H1N1)pdm09 viruses with NA-H275Y were detected in 15 states, albeit at a low frequency (0.53%). They belonged to several phylogenetic groups, with hemagglutinin (HA) subclade D.3.1 combined with either NA subclade D.1 or D.2 being most common. Based on shared sequence data, nearly all H275Y viruses from Australia, Canada, and Chile also belonged to these HA and NA subclades. Conversely, most H275Y viruses (68/81) from China belonged to HA subclade C.1.9 and NA subclade D and shared the permissive mutation R257K. Influenza polymerase acidic (PA) mutations conferring 4- to 92-fold decreased baloxavir susceptibility were detected in nine influenza A viruses. Viruses with PA-I38T showed mild attenuation of replicative fitness in three cell lines. Based on available data, NA-H275Y and PA-I38T viruses were collected from patients with no exposure to antivirals. Baseline susceptibility to all US-approved influenza antivirals remained largely unchanged compared to previous seasons. All swine-origin viruses detected in the US had adamantane resistance-conferring marker, M2-S31N, but remained susceptible to other approved antivirals. Monitoring antiviral susceptibility has substantially improved with increased sequencing capacities and bioinformatic support at public health laboratories. Information gained through influenza surveillance has been used to guide recommendations on antiviral use.

Source: 

Link: https://journals.asm.org/doi/10.1128/spectrum.01514-26

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#Spain, Ministry of Health is strengthening #prevention, #preparedness and response to #animal-borne #influenza with a national plan (Min. Health, July 16 '26)

 

    Madrid, July 16, 2026.- The Public Health Commission has approved the State Plan against infections by influenza viruses of zoonotic origin: Prevention, Surveillance and Control, which establishes a common framework for prevention, surveillance, early detection and response to influenza viruses that circulate in animals and can be transmitted to people.

    The Plan adopts the "One Health" approach and establishes a joint response across the fields of human health, animal health, and the environment. Its objective is to improve coordination among the different sectors at the national, regional, and local levels, and to ensure that epidemiological, microbiological, and environmental information is integrated, up-to-date, and readily available to facilitate the early implementation of control measures.

    The document has been coordinated by the Center for Coordination of Health Alerts and Emergencies (CCAES) of the Ministry of Health and prepared jointly with the Ministries of Agriculture, Fisheries and Food and for Ecological Transition and the Demographic Challenge, the Carlos III Health Institute, the Spanish Agency for Food Safety and Nutrition and other units involved in the prevention and management of these risks.

    Zoonotic influenza viruses circulate among animals. Transmission to humans remains infrequent and is usually linked to direct contact with infected animals, their secretions, or contaminated environments. However, their ability to mutate and exchange genetic material necessitates continuous surveillance, especially given the increased detection of these viruses in various mammal species.

    The Plan organizes the actions into four scenarios , which allow the measures to be progressively adapted to the epidemiological situation of each territory.

    Scenario 0 corresponds to a situation with no detected infections in animals or people and focuses on ordinary actions of prevention, surveillance, training and maintenance of diagnostic capabilities.

    Scenario 1 is activated upon detection of outbreaks in wild or captive animals. It distinguishes between isolated outbreaks in birds, multiple outbreaks distributed across a territory, and detections in wild mammals.

    Scenario 2 considers outbreaks in domestic animals and also differentiates between isolated outbreaks in birds, multiple outbreaks, and detections in domestic mammals.

    Finally, scenario 3 applies when a human infection is identified. In this case, a distinction is made between cases with known exposure to animals or contaminated environments, those where no risk exposure is identified, and cases associated with contact with another infected person, which would imply possible limited human-to-human transmission.

    The scenarios are not mutually exclusive and may be applied simultaneously in the same territory. Each autonomous community will conduct its own risk assessment to determine the necessary measures in each affected province, community, or geographical area.

    The Plan envisions the creation of a Permanent State Committee for Coordination and Monitoring , chaired and technically coordinated by the CCAES, responsible for reviewing preparedness and response measures, promoting common protocols, conducting joint risk assessments, and evaluating the Plan's effectiveness. Furthermore, it recommends that the autonomous communities establish equivalent bodies to coordinate actions related to public health, animal health, the environment, food safety, and occupational health.

    This body will include representatives from the competent departments in public health, animal health, biodiversity, food safety, occupational health, medicines and health products and epidemiological and microbiological surveillance, as well as from the autonomous communities, the Spanish Federation of Municipalities and Provinces and experts.

    Human health measures focus especially on people who, due to their professional activity, may come into contact with infected animals, their secretions or contaminated materials, such as livestock farm personnel, veterinary professionals, environmental agents or zoo workers.

    Companies must assess the risk, provide the necessary protective equipment, and ensure health monitoring. Occupational risk prevention services will identify and monitor exposed personnel in the event of outbreaks in animals and, where appropriate, may recommend PCR tests, preventive antiviral treatment, or vaccination against zoonotic viruses.

    The Plan also maintains the recommendation for seasonal flu vaccination for those who work in direct contact with animals, with the aim of reducing the risk of coinfection by human and animal flu viruses.

    In the animal sector , the Plan strengthens surveillance of wild and domestic birds and mammals, as well as genomic analysis of viruses to detect changes that could increase their transmissibility. In the event of outbreaks on farms, biosecurity measures, movement controls, confinement, and, where appropriate, vaccination will be implemented.

    In parks and urban or peri-urban areas, protocols will be established to safely remove sick or dead animals, clean and disinfect affected areas, and inform the public. It is recommended not to touch or handle them and to report their presence to the appropriate authorities.

    The Plan incorporates risk communication and community participation as one of its five main components. To this end, an inter-institutional communication group will be established, websites with updated information will be created, and campaigns will be developed targeting both the general public and the professional sectors with the greatest exposure.

    Media and social media will also be monitored to detect and respond to rumors, false content, or unverified information. In higher-risk scenarios, an official spokesperson will be appointed, information will be updated daily, and, when necessary, a citizen hotline will be activated.

    The Permanent State Committee will develop the indicators that will allow the evaluation of preparedness and response, as well as compliance with the Plan in its various components and at the state and regional levels.

    In the last year, more than 150 outbreaks of avian influenza have been detected in Spain, mostly in wild birds, although outbreaks have also been recorded in poultry, leading to the culling of thousands of animals. Despite the increased circulation of the virus among birds, Spain has not registered any human cases of avian influenza to date. Regarding swine influenza, three human cases of infection have been identified in Spain since 2009.

    The new Plan will strengthen prevention, early detection and coordinated response to any changes in the epidemiological situation.

Source: 

Link: https://www.sanidad.gob.es/gabinete/notasPrensa.do?id=6965

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Occupationally Exposed and General #Population #Antibody #Profiles to #Influenza A Viruses Circulating in #Swine as Indication of Zoonotic #Risk

 

Abstract

Persons with occupational exposure to swine might be at disproportionate risk for zoonotic swine influenza A virus. To evaluate human antibody responses, we tested serum or plasma from swine veterinarian, farm employee, and general population cohorts by hemagglutination inhibition assays against representative swine and human seasonal influenza vaccine strains. We analyzed hemagglutination inhibition data by antigenic cartography to assess strain relationships and reproduction number modeling to evaluate pandemic potential using age-stratified immunity profiles. Occupationally exposed groups had lower human seasonal vaccine uptake (45.5% vs. 70%) and lower odds of seropositivity to several H1 and H3 strains from swine than did general population cohorts. One swine strain exhibited significant antigenic drift (3.62 antigenic units) from its nearest vaccine strain. Multiple strains required lower reproduction number thresholds for pandemic spread (1.09–1.35) than recorded pandemic strains (1.46–1.80), demonstrating that population immunity gaps heighten zoonotic risk to circulating swine H1 and H3 strains.

Source: 

Link: https://wwwnc.cdc.gov/eid/article/32/8/25-1995_article

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# Influenza at #human - #animal #interface - Summary and #risk #assessment, from 13 June to 7 July 2026 (WHO): 1 new case of #H5 virus, 2 of #H9N2 and one of #H3N2v

 

Influenza at the human-animal interface - Summary and risk assessment, from 13 June to 7 July 2026 {1} 

    • New human cases {2}: 

        ° From 13 June to 7 July 2026, based on reporting date, detections of influenza A(H5) in one human, influenza A(H9N2) in two humans, and an influenza A(H3N2) variant ((H3N2)v) virus in one human were officially reported. 

    • Circulation of influenza viruses with zoonotic potential in animals: 

        ° High pathogenicity avian influenza (HPAI) events in poultry and non-poultry animal species continue to be reported to the World Organisation for Animal Health (WOAH).{3} 

        ° The Food and Agriculture Organization of the United Nations (FAO) also provides a global update on avian influenza viruses with pandemic potential.{4} 

        ° Additionally, low pathogenicity avian influenza viruses as well as swine influenza viruses continue to circulate in animal populations. 

    • Risk assessment {5}: 

        ° There have been no reports of sustained human-to-human transmission associated with the above-mentioned human infection events. 

        ° Based on information available at the time of this risk assessment update, the overall public health risk from currently known influenza A viruses detected at the human-animal interface has not changed and - At present, these viruses are not thought to be capable of sustained human-to-human transmission, although this could change as they evolve. 

        ° Although human infections with viruses of animal origin are infrequent, they are not unexpected at the human-animal interface.  

    • IHR compliance {6}: 

        ° This includes any influenza A virus that has demonstrated the capacity to infect a human and its haemagglutinin (HA) gene (or protein) is not a mutated form of those, i.e. A(H1) or A(H3), circulating widely in the human population. 

        ° Information from these notifications is critical to inform risk assessments for influenza at the human-animal interface.  

Avian influenza viruses in humans 

A(H5), Bangladesh   

    ° On 15 June 2026, Bangladesh notified WHO of one laboratory-confirmed human case of avian influenza A(H5) infection in Bangladesh in a child from Sylhet Division. 

    ° The case was detected notified through the National Influenza Surveillance, Bangladesh (NISB) platform as an influenza likeillness (ILI) case.    

    ° The patient developed respiratory symptoms on 17 May 2026, received outpatient healthcare on 20 May. 

    ° A clinical sample was collected that day and was received by the Institute of Epidemiology, Disease Control and Research (IEDCR) on 4 June as part of routine surveillance. 

    ° The sample tested positive for influenza A(H5) virus by real-time reverse transcription polymerase chain reaction (RTPCR) on 11 June.    

    ° The patient is now in good health and reported no travel history and no history of exposure to poultry. 

    ° However, poultry deaths were reported in the area surrounding the patient’s residence. 

    ° The outbreak investigation team identified and followed close and possible contacts. 

    ° Samples from some of the close contacts as well as animal and environmental samples were collected for testing for influenza. 

    ° All contacts remained asymptomatic and all samples tested negative for influenza.    

    ° This is the third laboratory-confirmed human case of avian influenza A(H5) reported in Bangladesh in 2026, and the 15th human case of avian influenza A(H5) reported to WHO from Bangladesh since 2008, including two fatal cases, one reported in 2013 and one in 2026.  

Risk assessment for avian influenza A(H5) viruses:

1. What is the current global public health risk of additional human cases of infection with avian influenza A(H5) viruses?    
• Most human infections so far have been reported in people exposed to A(H5) viruses, for example, through contact with infected poultry or contaminated environments, including live poultry markets, and occasionally infected mammals and contaminated environments. 
• As long as the viruses continue to be detected in animals and related environments humans are exposed to, further human cases associated with such exposures are expected but remain unusual. 
• The impact for public health if additional sporadic cases are detected is minimal. 
• The current overall global public health risk is low.  
2. What is the likelihood of sustained human-to-human transmission of avian influenza A(H5) viruses related to the events above?    
• No sustained human-to-human transmission  has  been identified associated with the recent reported human infections with avian influenza A(H5) viruses.
•  There has been no reported human-to-human transmission of A(H5N1) viruses since 2007, although there may be gaps in investigations.
•  In 2007 and the years prior, small clusters of A(H5) virus infections in humans were reported, including some involving health care workers, where limited human-to-human transmission could not be excluded; however, sustained human-to-human transmission was not reported.
•  Current evidence suggests that influenza A(H5) viruses related to these events did not acquire the ability to efficiently transmit between people.    
3. What is the likelihood of international spread of avian influenza A(H5) viruses by travellers?    
• Should infected individuals from affected areas travel internationally, their infection may be detected in another country during travel or after arrival. 
• If this were to occur, further communitylevel spread is considered unlikely as current evidence suggests these viruses have not acquired the ability to transmit easily among humans.    

A(H9N2), China  

    ° Between 12 and 23 June 2026, two laboratory-confirmed cases of A(H9N2) virus infection were detected in China. 

    ° Both cases had mild illness and were hospitalized in isolation wards at the time of reporting. 

{Click on Image to Enlarge}

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    ° Both cases had exposure to local live bird markets. 

    ° Samples from environments associated with the likely area of exposure of the cases tested positive for A(H9) viruses. 

    ° No further cases were detected among contacts of these cases.   

Risk assessment for avian influenza A(H9N2):  

1. What is the global public health risk of additional human cases of infection with avian influenza A(H9N2) viruses?  
• Most human cases follow exposure to the A(H9N2) virus through contact with infected poultry or contaminated environments. 
• Most human infections of A(H9N2) to date have resulted in mild clinical illness. 
• Since the virus is endemic in poultry in multiple countries in Africa and Asia, additional human cases associated with exposure to infected poultry or contaminated environments are expected but remain unusual. 
• The impact to public health if additional sporadic cases are detected is minimal. 
• The overall global public health risk is low.  
2. What is the likelihood of sustained human-to-human transmission of avian influenza A(H9N2) viruses related to these events?  
• At the present time, no sustained human-to-human transmission has been identified associated with the recently reported human infections with A(H9N2) viruses. 
• Current evidence suggests that A(H9N2) viruses from these cases did not acquire the ability of sustained transmission among humans.  
3. What is the likelihood of international spread of avian influenza A(H9N2) virus by travellers?  
• Should infected individuals from affected areas travel internationally, their infection may be detected in another country during travel or after arrival. 
• If this were to occur, further community level spread is considered unlikely as current evidence suggests the A(H9N2) virus subtype has not acquired the ability to transmit easily among humans.  

Swine influenza viruses in humans 

Influenza A(H3N2)v, Brazil  

    ° On 25 June 2026, Brazil notified PAHO/WHO of a laboratory-confirmed human infection with an influenza A(H3N2)v virus detected in a child in Santa Catarina state. 

    ° The patient had symptom onset on 12 June 2026 and due to worsening respiratory symptoms, healthcare was sought on 16 June. 

    ° The patient was referred for hospital admission with a diagnosis of Severe Acute Respiratory Infection (SARI). 

    ° Upon admission, an antigen test confirmed influenza A and the patient was placed in a private respiratory isolation room and antiviral treatment was initiated. 

    ° The patient was discharged on 19 June.  

    ° A nasopharyngeal swab sample was collected on 16 June and sent to the State public health laboratory for real-time RT-PCR. 

    ° On 18 June, a swine-origin influenza H3 variant was suspected, and the sample was sent to the Laboratory of Respiratory Viruses, Exanthems, Enteroviruses, and Viral Emergencies (LVRE) at the Oswaldo Cruz Institute (Fiocruz/Rio de Janeiro) on 19 June. 

    ° Analyses confirmed the presence of an influenza A(H3N2)v virus via molecular testing and genomic sequencing. 

    ° An investigation by the state and municipality epidemiological surveillance team found that all contacts were asymptomatic before, during and after the child’s illness. 

    ° The child's grandfather worked at a swine nursery housing approximately 5,000 animals, though he noted that sanitary barriers were in place. 

    ° The child frequently visited the grandfather's home and had contact with him several days a week.  

    ° This is the first human A(H3N2)v infection detected in the Brazil in 2026 and the first case reported in the state of Santa Catarina. 

Risk assessment for swine influenza viruses:    

1. What is the public health risk of additional human cases of infection with swine influenza viruses?    
• Swine influenza viruses circulate in swine populations in many regions of the world. 
• Depending on geographic location, the genetic characteristics of these viruses differ. 
• Most human cases are exposed to swine influenza viruses through contact with infected animals or contaminated environments. 
• Human infection tends to result in mild clinical illness in most cases. 
• Since these viruses continue to be detected in swine populations, further human cases are expected.
•  The impact to public health if additional sporadic cases are detected is minimal. 
• The overall risk of additional sporadic human cases is low.    
2. What is the likelihood of sustained human-to-human transmission of swine influenza viruses?     
• No sustained human-to-human transmission was identified associated with the event described above. 
• Current evidence suggests that contemporary swine influenza viruses have not acquired the ability of sustained transmission among humans.   
3. What is the likelihood of international spread of swine influenza viruses by travellers?     
• Should infected individuals from affected areas travel internationally, their infection may be detected in another country during travel or after arrival. 
• If this were to occur, further community level spread is considered unlikely as current evidence suggests that these viruses have not acquired the ability to transmit easily among humans.   

Overall risk management recommendations: 

    ° Surveillance and investigations 

        • Due to the constantly evolving nature of influenza viruses, WHO continues to stress the importance of global strategic surveillance in animals and humans to detect virologic, epidemiologic and clinical changes associated with circulating influenza viruses that may affect human (or animal) health. 

            Continued vigilance is needed within affected and neighbouring areas to detect infections in animals and humans. 

            Close collaboration with the animal health and environment sectors is essential to understand the extent of the risk of human exposure and to prevent and control the spread of animal influenza. 

            WHO has published guidance on surveillance for human infections with avian influenza A(H5) viruses. 

        • As the extent of influenza virus circulation in animals is not clear, epidemiologic and virologic surveillance and the follow-up of suspected human cases should continue systematically. 

            Guidance on investigation of non-seasonal influenza and other emerging acute respiratory diseases has been published on the WHO website. 

        • Countries should: 

            - increase avian influenza surveillance in domestic and wild birds, 

            - enhance surveillance for early detection in cattle populations in countries where HPAI is known to be circulating, include HPAI as a differential diagnosis in non-avian species, including cattle and other livestock populations, with high risk of exposure to HPAI viruses; 

            - monitor and investigate cases in non-avian species, including livestock, 

            - report cases of HPAI in all animal species, including unusual hosts, to WOAH and other international organizations, 

            - share genetic sequences of avian influenza viruses in publicly available databases, 

            - implement preventive and early response measures to break the HPAI transmission cycle among animals through movement restrictions of infected livestock holdings and strict biosecurity measures in all holdings, 

            - employ good production and hygiene practices when handing animal products, and protect persons in contact with suspected/infected animals.{7} 

            - More guidance can be found from WOAH and FAO. 

        • When there has been human exposure to a known outbreak of an influenza A virus in domestic poultry, wild birds or other animals – or when there has been an identified human case of infection with such a virus – enhanced surveillance in potentially exposed human populations becomes necessary. 

            - Enhanced surveillance should consider the health care seeking behaviour of the population, and could include a range of active and passive health care and/or communitybased approaches, including: enhanced surveillance in local influenza-like illness (ILI)/SARI systems, active screening in hospitals and of groups that may be at higher occupational risk of exposure, and inclusion of other sources such as traditional healers, private practitioners and private diagnostic laboratories. 

        • Vigilance for the emergence of novel influenza viruses with pandemic potential should be maintained at all times including during a non-influenza emergency. In the context of the cocirculation of SARS-CoV-2 and influenza viruses, WHO has updated and published practical guidance for integrated surveillance. 

    ° Notifying WHO 

        • All human infections caused by a new subtype of influenza virus are notifiable under the International Health Regulations (IHR, 2005).{8,9} State Parties to the IHR (2005) are required to immediately notify WHO of any laboratory-confirmed {10} case of a recent human infection caused by an influenza A virus with the potential to cause a pandemic {11}. Evidence of illness is not required for this report. Evidence of illness is not required for this report. 

        • WHO published the case definition for human infections with avian influenza A(H5) virus requiring notification under IHR (2005): https://www.who.int/teams/global-influenzaprogramme/avian-influenza/case-definitions. 

    ° Virus sharing and risk assessment 

        • It is critical that these influenza viruses from animals or from humans are fully characterized in appropriate animal or human health influenza reference laboratories. Under WHO’s Pandemic Influenza Preparedness (PIP) Framework, Member States are expected to share influenza viruses with pandemic potential on a timely basis {12} with a WHO Collaborating Centre for influenza of GISRS. The viruses are used by the public health laboratories to assess the risk of pandemic influenza and to develop candidate vaccine viruses.  

        • The Tool for Influenza Pandemic Risk Assessment (TIPRA) provides an in-depth assessment of risk associated with some zoonotic influenza viruses – notably the likelihood of the virus gaining human-to-human transmissibility, and the impact should the virus gain such transmissibility. TIPRA maps relative risk amongst viruses assessed using multiple risk elements. The results of TIPRA complement those of the risk assessment provided here, and those of prior TIPRA risk assessments are published at http://www.who.int/teams/global-influenza-programme/avianinfluenza/tool-for-influenza-pandemic-risk-assessment-(tipra).  

    ° Risk reduction 

        • Given the observed extent and frequency of avian influenza in poultry, wild birds and some wild and domestic mammals, the public should avoid contact with animals that are sick or dead from unknown causes, including wild animals, and should report dead birds and mammals or request their removal by contacting local wildlife or veterinary authorities.  

        • Eggs, poultry meat and other poultry food products should be properly cooked and properly handled during food preparation. Due to the potential health risks to consumers, raw milk should be avoided. WHO advises consuming pasteurized milk. If pasteurized milk isn’t available, heating raw milk until it boils makes it safer for consumption. 

        • WHO has published practical interim guidance to reduce the risk of infection in people exposed to avian influenza viruses. 

    ° Trade and travellers 

        • WHO advises that travellers to countries with known outbreaks of animal influenza should avoid farms, contact with animals in live animal markets, entering areas where animals may be slaughtered, or contact with any surfaces that appear to be contaminated with animal excreta. Travelers should also wash their hands often with soap and water. All individuals should follow good food safety and hygiene practices.  

        • WHO does not advise special traveller screening at points of entry or restrictions with regards to the current situation of influenza viruses at the human-animal interface. For recommendations on safe trade in animals and related products from countries affected by these influenza viruses, refer to WOAH guidance.  

Links:  

° WHO Human-Animal Interface web page https://www.who.int/teams/global-influenza-programme/avian-influenza 

° WHO Influenza (Avian and other zoonotic) fact sheet https://www.who.int/news-room/fact-sheets/detail/influenza-(avian-and-other-zoonotic) 

° WHO Protocol to investigate non-seasonal influenza and other emerging acute respiratory diseases https://www.who.int/publications/i/item/WHO-WHE-IHM-GIP-2018.2 

° WHO Public health resource pack for countries experiencing outbreaks of influenza in animals:  https://www.who.int/publications/i/item/9789240076884 

° Cumulative Number of Confirmed Human Cases of Avian Influenza A(H5N1) Reported to WHO  https://www.who.int/teams/global-influenza-programme/avian-influenza/avian-a-h5n1-virus 

° Avian Influenza A(H7N9) Information https://www.who.int/teams/global-influenza-programme/avian-influenza/avian-influenza-a-(h7n9)virus 

° World Organisation of Animal Health (WOAH) web page: Avian Influenza  https://www.woah.org/en/home/ 

° Food and Agriculture Organization of the United Nations (FAO) webpage: Avian Influenza https://www.fao.org/animal-health/avian-flu-qa/en/ 

° WOAH/FAO Network of Expertise on Animal Influenza (OFFLU) http://www.offlu.org/ 

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{1} This summary and assessment covers information confirmed during this period and may include information received outside of this period. 

{2} For epidemiological and virological features of human infections with animal influenza viruses not reported in this assessment, see the reports on human cases of influenza at the human-animal interface published in the Weekly Epidemiological Record here.  

{3} World Organisation for Animal Health (WOAH). Avian influenza. Global situation. Available at: https://www.woah.org/en/disease/avian-influenza/#ui-id-2. 

{4} Food and Agriculture Organization of the United Nations (FAO). Global Avian Influenza Viruses with Zoonotic Potential situation update. Available at: https://www.fao.org/animal-health/situation-updates/global-aiv-withzoonotic-potential. 

{5} World Health Organization (2012). Rapid risk assessment of acute public health events. World Health Organization. Available at: https://iris.who.int/handle/10665/70810. 

{6} World Health Organization. Case definitions for the four diseases requiring notification in all circumstances under the International Health Regulations (2005). Available at: https://www.who.int/publications/m/item/case-definitions-for-the-four-diseases-requiring-notification-towho-in-all-circumstances-under-the-ihr-(2005).  

{7} World Organisation for Animal Health. Statement on High Pathogenicity Avian Influenza in Cattle, 6 December 2024 (https://www.woah.org/en/high-pathogenicity-avian-influenza-hpai-in-cattle/). 

{8} World Health Organization. International Health Regulations (2005), as amended through resolutions WHA67.13 (2014), WHA75.12 (2022), and WHA77.17 (2024) (https://apps.who.int/gb/bd/pdf_files/IHR_20142022-2024-en.pdf). 

{9} World Health Organization. Case definitions for the four diseases requiring notification in all circumstances under the International Health Regulations (2005) (https://www.who.int/publications/m/item/casedefinitions-for-the-four-diseases-requiring-notification-to-who-in-all-circumstances-under-the-ihr-(2005)). 

{10} World Health Organization. Manual for the laboratory diagnosis and virological surveillance of influenza (2011) (https://apps.who.int/iris/handle/10665/44518). 

{11} World Health Organization. Pandemic influenza preparedness framework for the sharing of influenza viruses and access to vaccines and other benefits, 2nd edition (https://iris.who.int/handle/10665/341850). 

{12} World Health Organization. Operational guidance on sharing influenza viruses with human pandemic potential (IVPP) under the Pandemic Influenza Preparedness (PIP) Framework (2017) (https://apps.who.int/iris/handle/10665/259402). 

Source: 

Link: https://www.who.int/publications/m/item/influenza-at-the-human-animal-interface-summary-and-assessment--7-july-2026

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