Abstract
Poultry workers in Washington, USA, were infected with highly pathogenic avian influenza A(H5N1) virus and recovered. The viruses were clade 2.3.4.4b genotype D1.1, closely related to viruses causing poultry outbreaks. Continued surveillance and testing for influenza A(H5) clade 2.3.4.4b viruses remain essential for risk assessment and pandemic preparedness of zoonotic influenza viruses.
Source:
Link: https://wwwnc.cdc.gov/eid/article/31/12/25-1118_article
____
I am an Italian blogger, active since 2005 with main focus on emerging infectious diseases such as avian influenza, SARS, antibiotics resistance, and many other global Health issues. Other fields of interest are: climate change, global warming, geological and biological sciences. My activity consists mainly in collection and analysis of news, public services updates, confronting sources and making decision about what are the 'signals' of an impending crisis (an outbreak, for example). When a signal is detected, I follow traces during the entire course of an event. I started in 2005 my blog ''A TIME'S MEMORY'', now with more than 40,000 posts and 3 millions of web interactions. Subsequently I added an Italian Language blog, then discontinued because of very low traffic and interest. I contributed for seven years to a public forum (FluTrackers.com) in the midst of the Ebola epidemic in West Africa in 2014, I left the site to continue alone my data tracking job.
5 December 2025
Situation at a glance
On 15 November 2025, WHO was notified of the 71st confirmed human case with influenza A(H5) since early 2024 in the United States of America— the first human case reported in the United States of America since February 2025.
On 20 November, U.S. Centers for Disease Control and Prevention (CDC) laboratory sequencing verified the virus as influenza A(H5N5), representing the first globally reported human case caused by an influenza A(H5N5) virus.
The investigation by health authorities in the United States of America is ongoing.
Contact tracing identified no further cases amongst contacts, and there is currently no evidence of human-to-human transmission.
Due to the constantly evolving nature of influenza viruses, WHO continues to stress the importance of global surveillance to detect and monitor virological (including genomics), epidemiological and clinical changes associated with emerging or circulating influenza viruses that may affect human health and timely virus sharing for risk assessment.
Based on available information, the WHO currently assesses the overall public health risk posed by A(H5) viruses as low.
However, for individuals with occupational risk of exposure, the risk of infection is considered low to moderate.
Description of the situation
On 15 November 2025, WHO was notified of a confirmed human infection with influenza A(H5) in the United States of America—the first reported in the country since February 2025 and the 71st since early 2024.
On 20 November, CDC laboratory sequencing verified the virus as influenza A(H5N5), representing the first human case of this subtype reported globally.
The patient was an adult with underlying medical conditions residing in Washington State.
The patient developed symptoms including fever during the week ending 25 October 2025.
During the week ending 8 November 2025, the patient was hospitalized with a serious illness and subsequently died on 21 November.
Respiratory specimens collected at the healthcare facility tested positive for influenza A virus by RT-PCR and were presumptive positive for influenza A(H5) at the University of Washington.
The specimens were sent to the Washington State Public Health Laboratory, where influenza A(H5) was confirmed using the CDC influenza A(H5) assay.
The sample was received at the CDC on 19 November.
Sequencing conducted at the University of Washington and at the CDC indicated this was an influenza A(H5N5) virus belonging to the H5 haemagglutinin (HA) clade 2.3.4.4b[1].
Public health investigation revealed that the patient kept backyard poultry and domestic birds.
Additional epidemiological investigations are under way and include active monitoring of anyone who was in close contact with the patient.
Epidemiology
Animal influenza viruses typically circulate within animal populations, but some have the potential to infect humans.
Human infections are predominantly acquired through direct contact with infected animals or exposure to contaminated environments.
Based on the original host species, influenza A viruses can be categorized such as avian influenza, swine influenza, and other animal-origin influenza subtypes.
Human infection with avian influenza viruses may result in a spectrum of illness, ranging from mild upper respiratory tract symptoms to severe, life-threatening conditions.
Clinical manifestations may include conjunctivitis, respiratory, gastrointestinal symptoms, encephalitis (brain swelling), and encephalopathy (brain damage).
In some cases, asymptomatic infections with the virus have been reported in individuals with known exposure to infected animals and environments.
A definitive diagnosis of human avian influenza infection requires laboratory confirmation.
WHO regularly updates its technical guidance on the detection of zoonotic influenza, utilizing molecular diagnostic methods such as RT-PCR.
Clinical evidence indicates that certain antiviral agents, particularly neuraminidase inhibitors (e.g., oseltamivir, zanamivir), have been shown to shorten the duration of viral replication and improve patient outcomes in some cases.
This antiviral agent should be administered within 48 hours of symptom onset.
High pathogenicity avian influenza A(H5) clade 2.3.4.4b A(H5N5) viruses have been detected in North America in wild birds and wild mammals since at least 2023.[2]
This is the first laboratory-confirmed human infection with an influenza A(H5N5) virus in the United States of America and reported globally.
Public health response
The CDC and State public health officials have initiated several public health response measures:
-- Public health officials are conducting surveillance in the area, that included additional case investigations and contact tracing.
-- Since March 2024, at least 30,100 people have been monitored, and at least 1260 have been tested after exposure to infected animals in the USA.
-- The CDC conducts enhanced routine surveillance to detect and monitor influenza activity, including infections caused by novel influenza viruses such as avian influenza A(H5).
-- The CDC recommends that state and local public health departments monitor individuals exposed to birds or other animals (including livestock) suspected of being infected with avian influenza A viruses for the onset of signs and symptoms for up to 10 days after their last exposure. Individuals who develop signs or symptoms of respiratory illness and/or conjunctivitis should be tested for influenza.
-- The CDC has issued recommendations for the public to avoid unprotected contact with sick or dead animals, including wild birds, poultry, other domestic fowl, and other wild or domestic animals, as well as animal droppings, litter, or materials contaminated by birds or other animals suspected of being infected with the influenza A(H5) virus.
-- The CDC has interim recommendations for prevention, monitoring, and public health investigations of avian influenza A(H5) virus infections in people. The CDC has also updated recommendations for occupational protection and the use of personal protective equipment (PPE).
WHO risk assessment
Human infections with avian influenza A(H5) viruses are considered unusual, as A(H5) viruses remain primarily avian influenza viruses.
However, in rare cases, individuals exposed to infected animals or contaminated environments can become infected with A(H5) viruses.
Influenza A(H5N5) viruses are detected in birds, including wild birds and domestic poultry, and sometimes in non-human mammals.
When avian influenza viruses circulate in poultry populations, there is an inherent risk of human infection through exposure to infected birds or contaminated environments.
As such, sporadic human cases are expected.
The case had underlying conditions and subsequently died.
The investigation by health authorities in the United States of America is ongoing and included contact tracing which identified no further cases amongst contacts, and there is currently no evidence of human-to-human transmission.
This is the 71st confirmed human case of A(H5) in the United States of America since early 2024, and the first since February 2025.
To date, no human-to-human transmission has been identified in any of the A(H5) cases reported in the United States of America.
From a global perspective, while a few events with limited human-to-human transmission of zoonotic influenza A(H5) have been described between 1997 and 2007, sustained human-to-human transmission has not been detected to date.
Based on available information, the WHO currently assesses the overall public health risk posed by A(H5) viruses as low. However, for individuals with occupational risk of exposure, the risk of infection is considered low to moderate.
The risk assessment will be updated as needed, based on any new epidemiological or virological information related to this event.
WHO advice
This event does not change the current WHO recommendations on public health measures and surveillance of influenza.
Given the current situation of influenza viruses at the human-animal-environmental interface, WHO does not recommend special traveler screening at points of entry or any restrictions.
Due to the constantly evolving nature of influenza viruses, WHO continues to stress the importance of global surveillance to detect and monitor virological (including genomics), epidemiological and clinical changes associated with emerging or circulating influenza viruses that may affect human health and timely virus sharing for risk assessment.
When humans have been exposed to an influenza A virus outbreak in domestic poultry, wild birds, or other animals or when a human case of infection is identified, enhanced surveillance of potentially exposed human populations becomes necessary. This surveillance should consider the healthcare-seeking behaviour of the population and may include a range of active and passive approaches, such as enhanced surveillance in influenza-like illness (ILI)/severe acute respiratory infection (SARI) systems, active screening in hospitals, and among groups at higher occupational risk of exposure. It should also consider other sources, such as traditional healers, private practitioners, and private diagnostic laboratories.
Given the observed widespread occurrence of avian influenza in poultry, wild birds and some wild and domestic mammals, the public should avoid contact with any sick or dead animals.
Individuals should report deceased birds and mammals or request their removal by contacting local wildlife or veterinary authorities.
Eggs, poultry meat, and other poultry products should be properly cooked and handled during food preparation.
Due to potential health risks, consumption of raw milk should be avoided. WHO advises consuming pasteurized milk and if pasteurized milk is not available, heating raw milk until it boils makes it safer for consumption.
In the case of a confirmed or suspected human infection caused by a novel influenza A virus with pandemic potential, including avian influenza viruses, early clinical management, a thorough epidemiologic investigation of animal exposure history, travel, and contact tracing should be conducted even while awaiting the confirmatory laboratory results.
The epidemiologic investigation should also include early identification of unusual events that could signal person-to-person transmission of the novel virus.
Clinical samples collected from confirmed or suspected cases should be tested and sent to a WHO Collaborating Center[3] for further characterization. Additional samples should be collected from animals, the environment or any foods suspected to be sources of infection.
WHO advises travelers to countries with known animal influenza outbreaks to avoid farms, live animal markets, areas where animals may be slaughtered and contact with any surfaces potentially contaminated by animal feces.
Travelers should also wash their hands frequently with soap and water and should follow good food safety and good food hygiene practices.
If infected individuals from affected areas travel internationally, their infection may be detected either during travel or upon arrival. However, further community level spread is considered unlikely, as this virus has not yet acquired the ability to transmit easily among humans.
Poultry workers should take additional health precautions as they are at higher risk of exposure to avian influenza and other zoonotic diseases due to their close contact with birds and potentially contaminated environments. Farm workers who have direct or close contact with animals or materials infected or contaminated with avian influenza A(H5) virus, should wear appropriate personal protective equipment (PPE) to minimize their risk of exposure.
All human infections caused by a novel influenza A virus subtype are notifiable under the International Health Regulations (IHR,2005) and State Parties to the IHR are required to immediately notify WHO within 24 hours of any laboratory-confirmed case of a recent human infection caused by an influenza A virus due to the potential to cause a pandemic. Evidence of illness is not required for this report. WHO has updated the influenza A(H5) confirmed case definition on the WHO website.
Currently, there are no readily available vaccines against influenza A(H5) virus for humans. Candidate vaccine viruses for pandemic preparedness have been selected against several A(H5) clades. Existing seasonal influenza vaccines are unlikely to provide protection to against avian influenza A(H5) viruses, based on currently available data. Close monitoring of the epidemiological situation and serological investigations are essential for assessing risk and adjusting risk management measures as needed..
WHO does not recommend any restriction on travel to or trade with the United States of America, based on the information available on the current event.
Further information
-- Centers for Disease Control and Prevention (CDC). H5 Bird Flu: Current Situation. Available from: https://www.cdc.gov/bird-flu/situation-summary/index.html
-- Centers for Disease Control and Prevention (CDC). Weekly US Influenza Surveillance Report: Key Updates for Week 46, ending November 15, 2025. Available from: https://www.cdc.gov/fluview/surveillance/2025-week-46.html
-- World Health Organization, Food and Agriculture Organization of the United Nations, & World Organization for Animal Health (July 2025). Updated joint FAO/WHO/WOAH assessment of recent influenza A(H5N1) virus events in animals and people. WHO, FAO, WOAH; 2025. Available from: https://cdn.who.int/media/docs/default-source/influenza/human-animal-interface-risk-assessments/fao-woah-who-joint-h5-assessment-july-2025.pdf?sfvrsn=fe76b74e_1&download=true
-- World Health Organization. Cumulative number of confirmed human cases of avian influenza A(H5N1) reported to WHO. Geneva: WHO; 2025. Available from: https://www.who.int/publications/m/item/cumulative-number-of-confirmed-human-cases-for-avian-influenza-a(h5n1)-reported-to-who--2003-2025--5-november-2025
-- United States Department of Agriculture, Animal and Plant Health Inspection Service. The Occurrence of Another Highly Pathogenic Avian Influenza (HPAI) Spillover from Wild Birds into Dairy Cattle. Washington, D.C.: USDA; 2025. Available from: https://www.aphis.usda.gov/sites/default/files/dairy-cattle-hpai-tech-brief.pdf
-- Centers for Disease Control and Prevention. Recommended composition of influenza virus vaccines for use in the southern hemisphere 2025 influenza season and development of candidate vaccine viruses for pandemic preparedness. Atlanta: CDC; 2025. Available from: https://cdn.who.int/media/docs/default-source/vcm-southern-hemisphere-recommendation-2025/202409_qanda_recommendation_final.pdf?sfvrsn=bd3d90b1_3
-- Pan American Health Organization / World Health Organization. Epidemiological Alert - Human infections caused by avian influenza A(H5N1) in the Region of the Americas - 5 June 2024. Washington, D.C.: PAHO/WHO; 2024. Available from: https://www.paho.org/en/documents/epidemiological-alert-human-infections-caused-avian-influenza-ah5n1-region-americas-5
-- Public Health Risk Assessment associated with the spread of zoonotic avian influenza A(H5N1) clade 2.3.4.4b in the Region of the Americas - 12 July 2024. Available from: https://www.paho.org/en/documents/public-health-risk-assessment-associated-spread-zoonotic-avian-influenza-ah5n1-clade
-- World Health Organization. Mosaic Respiratory Surveillance Framework. Geneva: WHO; 2024. Available from: https://www.who.int/initiatives/mosaic-respiratory-surveillance-framework/
-- World Health Organization. Practical interim guidance to reduce the risk of infection in people exposed to avian influenza viruses. Geneva: WHO; 2024. Available from: https://www.who.int/publications/i/item/B09116
-- World Health Organization. WHO case definition for human infections with avian influenza A(H5) virus requiring notification under IHR (2005) Geneva: WHO; 2024. Available from: https://www.who.int/teams/global-influenza-programme/avian-influenza/case-definitions
-- World Health Organization. Surveillance for human infections with avian influenza A(H5) viruses: objectives, case definitions, testing and reporting. Geneva: WHO; 2024. Available from: https://www.who.int/publications/i/item/B09337
-- World Health Organization. Case definitions for the four diseases requiring notification in all circumstances under the International Health Regulations (2005). Geneva: WHO; 2024. Available from: https://cdn.who.int/media/docs/default-source/documents/emergencies/case-definitions-ihr-four-diseases7f1ee707-3d13-4581-a1af-d5f44f86423a.pdf?sfvrsn=9c68df20_1&download=true
-- Animal and Plant Health Inspection Service. Confirmation of Highly Pathogenic Avian Influenza in Commercial and Backyard Flocks. Available from: Avian Influenza | Animal and Plant Health Inspection Service (usda.gov)
-- United States Department of Agriculture, Animal and Plant Health Inspection Service. Detections of Highly Pathogenic Avian Influenza in Mammals. Washington, D.C.: USDA; 2025. Available from: https://www.aphis.usda.gov/livestock-poultry-disease/avian/avian-influenza/hpai-detections/mammals
-- United States Department of Agriculture. Animal and Plant Health Inspection Service. HPAI Confirmed Cases in Livestock. Washington, D.C.: USDA; 2024. Available from: https://www.aphis.usda.gov/livestock-poultry-disease/avian/avian-influenza/hpai-detections/hpai-confirmed-cases-livestock
-- Pan American Health Organization / World Health Organization. Informe sobre el Grupo de Expertos para la CIPCIZA - Reunión de grupos de trabajo: Vigilancia, Laboratorio y Evaluación de riesgos intersectorial. Washington, D.C.: PAHO/WHO; 2025. Available from: https://www.paho.org/es/documentos/informe-sobre-grupo-expertos-para-cipciza-reunion-grupos-trabajo-vigilancia-laboratorio
-- Pan American Health Organization / World Health Organization. Colocación y retiro de EPP en trabajadores de granjas ante influenza aviar. Washington, D.C.: PAHO/WHO; 2025. Available from: https://www.paho.org/es/documentos/colocacion-retiro-epp-trabajadores-granjas-ante-influenza-aviar .
-- Pan American Health Organization / World Health Organization. Colocación y retiro de EPP en trabajadores de la salud ante influenza aviar. Washington, D.C.: PAHO/WHO; 2025. Available from: https://www.paho.org/es/documentos/colocacion-retiro-epp-trabajadores-salud-ante-influenza-aviar.
-- Pan American Health Organization / World Health Organization. Influenza at the Human-Animal Interface: PAHO Recommendations to Strengthen Intersectoral Work for Surveillance, Early Detection, and Investigation, 9 July 2020. Available from: https://iris.paho.org/handle/10665.2/52563
-- Pan American Health Organization / World Health Organization. Samples from patients suspected of Influenza A/H5 LABORATORY TESTING ALGORITHM. Available from: https://www.paho.org/en/documents/samples-patients-suspected-influenza-ah5-laboratory-testing-algorithm
-- Pan American Health Organization / World Health Organization. Technical note: Laboratory Diagnosis of Human Infection with Influenza A/H5. Available from: https://www.paho.org/en/documents/technical-note-laboratory-diagnosis-human-infection-influenza-ah5
-- Current technical information including monthly risk assessments at the Human-Animal Interface. Available from: https://www.who.int/teams/global-influenza-programme/avian-influenza/monthly-risk-assessment-summary
-- WHO. Zoonotic Influenza Outbreak Toolbox. Available from: https://www.who.int/emergencies/outbreak-toolkit/disease-outbreak-toolboxes/zoonotic-influenza-outbreak-toolbox
-- WHO. International Health Regulations (2005). Available from: http://www.who.int/ihr/publications/9789241596664/en/
-- WHO. Manual for the laboratory diagnosis and virological surveillance of influenza (2011). Available from: https://www.who.int/publications/i/item/manual-for-the-laboratory-diagnosis-and-virological-surveillance-of-influenza
-- Terms of Reference for National Influenza Centers of the Global Influenza Surveillance and Response System. Available from: https://www.who.int/initiatives/global-influenza-surveillance-and-response-system/national-influenza-centres
-- Pan American Health Organization / World Health Organization. Epidemiological Update: Avian Influenza A(H5N1) in the Americas Region, 15 November 2024. Washington, D.C.: PAHO/WHO; 2024. Available from: https://www.paho.org/en/documents/epidemiological-update-avian-influenza-ah5n1-americas-region-15-november-2024
-- Pan American Health Organization / World Health Organization. Report of the Regional Consultation for the Strengthening of Intersectoral Work in the Human-Animal Interface of Influenza. 22 March 2023. Washington, D.C.: PAHO/WHO; 2023. Available from: Report of the Regional Consultation for the Strengthening of Intersectoral Work in the Human-Animal Interface of Influenza. March 2023 - PAHO/WHO | Pan American Health Organization
-- Pan American Health Organization / World Health Organization. Strengthening the intersectoral work for Influenza at the Human Animal Interface in the Region of the Americas: Technical Questions and Answers. 19 May 2023. Washington, D.C.: PAHO/WHO; 2023. Available from: Strengthening the intersectoral work for Influenza at the Human Animal Interface in the Region of the Americas: Technical Questions and Answers - PAHO/WHO | Pan American Health Organization
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[1] Lam TT, Davis CT, WHO/WOAH/FAO H5 Evolution Working Group. Nomenclature updates to the hemagglutinin gene clade designations resulting from the continued evolution of high pathogenicity avian influenza A(H5) virus clades 2.3.2.1c and 2.3.4.4. bioRxiv. 2025 Nov 23;2025.11.23.690055. doi:10.1101/2025.11.23.690055.
[2] Erdelyan CNG, Kandeil A, Signore AV, et al. Multiple transatlantic incursions of highly pathogenic avian influenza clade 2.3.4.4b A(H5N5) virus into North America and spillover to mammals. Cell Rep. 2024 Jul 23;43(7):114479. doi:10.1016/j.celrep.2024.114479. Epub 2024 Jul 13. PMID:39003741; PMCID:PMC11305400
[3] World Health Organization. WHO Collaborating Centres and Essential Regulatory Laboratories in the Global Influenza Surveillance and Response System (GISRS) [Internet]. Geneva: WHO; 2025. Available from: https://www.who.int/initiatives/global-influenza-surveillance-and-response-system/who-collaboration-center-erl
___
Citable reference: World Health Organization (5 December 2025). Disease Outbreak News; Avian Influenza A(H5N5)- United States of America. Available at: https://www/who.int/emergencies/disease-outbreak-news/item/2025-DON590
Source:
Link: https://www.who.int/emergencies/disease-outbreak-news/item/2025-DON590
____
I am an Italian blogger, active since 2005 with main focus on emerging infectious diseases such as avian influenza, SARS, antibiotics resistance, and many other global Health issues. Other fields of interest are: climate change, global warming, geological and biological sciences. My activity consists mainly in collection and analysis of news, public services updates, confronting sources and making decision about what are the 'signals' of an impending crisis (an outbreak, for example). When a signal is detected, I follow traces during the entire course of an event. I started in 2005 my blog ''A TIME'S MEMORY'', now with more than 40,000 posts and 3 millions of web interactions. Subsequently I added an Italian Language blog, then discontinued because of very low traffic and interest. I contributed for seven years to a public forum (FluTrackers.com) in the midst of the Ebola epidemic in West Africa in 2014, I left the site to continue alone my data tracking job.
The person was infected with the H5N5 virus; the risk to the public remains low
OLYMPIA – A Grays Harbor County resident who was undergoing treatment for H5N5 avian influenza died today.
The Washington State Department of Health offers its heartfelt condolences to the person’s family and friends.
The person was an older adult with underlying health conditions.
Out of respect for the family’s privacy, we are not releasing their name, gender, or age.
The person had been hospitalized in King County since early November.
Testing at the UW Medicine Clinical Virology Lab identified the virus as H5N5, making this the first recorded infection with this variant in a person globally.
The result was confirmed by the Centers for Disease Control and Prevention (CDC).
The risk to the public remains low.
No other people involved have tested positive for avian influenza.
Public health officials will continue to monitor anyone who was in close contact with the patient for symptoms to ensure that human-to-human spread has not occurred.
There is no evidence of transmission of this virus between people.
The person had a backyard flock of mixed domestic birds.
DOH testing identified avian influenza virus in the environment of the flock, making exposure to the domestic poultry, their environment, or wild birds the most likely source of exposure for this patient.
People who had exposure to the backyard flock and environment are also being monitored for symptoms.
Avian influenza is a disease caused by influenza type A viruses, which naturally occur in wild aquatic birds around the world. These viruses can infect other bird species, and occasionally mammals, and can be deadly to domestic birds such as chickens and turkeys. On rare occasions, avian influenza viruses can infect people and make them sick.
People with backyard poultry should avoid contact with sick or dead birds and report illness in poultry to the Washington State Department of Agriculture (WSDA) by calling 1-800-606-3056 or reporting online.
Veterinarians should report sick or dead domestic animals or livestock suspected of having avian influenza to WSDA.
Avoid contact with sick or dead wildlife and report sick or dead wild birds or other animals to the Washington State Department of Fish & Wildlife.
Never handle or allow pets near dead birds or other wildlife.
Avoid eating raw or undercooked food products, such as unpasteurized (raw) milk or raw cheeses, and don’t feed these products to pets.
It is especially important that people who may have exposure to domestic or wild birds get a seasonal flu vaccine.
While the seasonal flu vaccine will not prevent bird flu infection, it reduces the risk of becoming sick with both human and avian influenza viruses at the same time.
Though unlikely, infection with both viruses could result in the emergence of an avian influenza virus that is more easily transmitted from person to person.
Seasonal flu vaccine is recommended for everyone six months and older.
Our website is your source for a healthy dose of information. Get updates by following us on social media.
Source:
Link: https://doh.wa.gov/newsroom/grays-harbor-county-resident-dies-complications-avian-influenza
____
I am an Italian blogger, active since 2005 with main focus on emerging infectious diseases such as avian influenza, SARS, antibiotics resistance, and many other global Health issues. Other fields of interest are: climate change, global warming, geological and biological sciences. My activity consists mainly in collection and analysis of news, public services updates, confronting sources and making decision about what are the 'signals' of an impending crisis (an outbreak, for example). When a signal is detected, I follow traces during the entire course of an event. I started in 2005 my blog ''A TIME'S MEMORY'', now with more than 40,000 posts and 3 millions of web interactions. Subsequently I added an Italian Language blog, then discontinued because of very low traffic and interest. I contributed for seven years to a public forum (FluTrackers.com) in the midst of the Ebola epidemic in West Africa in 2014, I left the site to continue alone my data tracking job.
{Excerpt}
Novel Influenza A Virus Infections
Two confirmed human infections with novel influenza A viruses were reported to CDC this week.
One infection with an influenza A(H5N5) virus was reported by the Washington State Department of Health and one infection with an influenza A(H1N2) variant (A(H1N2)v) virus was reported by the Vermont Department of Health.
One infection with an influenza A(H5N5) virus was reported by the Washington State Department of Public Health.
-- The case occurred in an individual aged ≥18 years.
-- This individual developed symptoms during the week ending October 25, 2025 (Week 43) and was hospitalized with their illness during the week ending November 8, 2025 (Week 45).
-- Respiratory specimens collected at the healthcare facility tested positive for influenza A and were presumptive positive for influenza A(H5) at the University of Washington.
-- The specimens were sent to the Washington State Public Health Laboratory where influenza A(H5) was confirmed using the CDC influenza A(H5) assay.
-- Sequencing conducted at the University of Washington and at the CDC indicated this was an influenza A(H5N5) virus.
-- The investigation by public health officials identified that the patient kept backyard poultry that had exposure to wild birds.
-- The patient remains hospitalized.
-- This is the twelfth confirmed influenza A(H5) case in Washington overall.
-- Prior confirmed cases in Washington were associated with commercial poultry exposure.
-- This is the 71st confirmed human case of A(H5) in the United States since early 2024 and the first human case reported in the United States since February 2025.
One infection with an influenza A(H1N2)v virus was reported by the Vermont Department of Health in an individual aged ≥18 years.
-- The individual developed symptoms and sought healthcare during the week ending October 4, 2025 (Week 40), was hospitalized but discharged on the same day, and has recovered from their illness.
-- The investigation conducted by state public health officials was unable to determine whether the individual had exposure to swine or other animals, or whether the patient's close contacts exhibited any illness.
-- No human-to-human transmission has been identified associated with this case.
-- 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/2025-week-46.html
____
I am an Italian blogger, active since 2005 with main focus on emerging infectious diseases such as avian influenza, SARS, antibiotics resistance, and many other global Health issues. Other fields of interest are: climate change, global warming, geological and biological sciences. My activity consists mainly in collection and analysis of news, public services updates, confronting sources and making decision about what are the 'signals' of an impending crisis (an outbreak, for example). When a signal is detected, I follow traces during the entire course of an event. I started in 2005 my blog ''A TIME'S MEMORY'', now with more than 40,000 posts and 3 millions of web interactions. Subsequently I added an Italian Language blog, then discontinued because of very low traffic and interest. I contributed for seven years to a public forum (FluTrackers.com) in the midst of the Ebola epidemic in West Africa in 2014, I left the site to continue alone my data tracking job.
For immediate release: November 14, 2025 (25-138)
First detection of this strain in a human, risk to the public remains low
Contact: DOH Communications
A Grays Harbor resident who was hospitalized with influenza symptoms in early November has been confirmed to have influenza A H5, a type of avian influenza.
Additional testing shows the virus to be H5N5, an avian influenza virus that has previously been reported in animals but never before in humans.
The Centers for Disease Control and Prevention (CDC) and DOH currently consider the risk to the public from avian influenza to be low.
The person is an older adult with underlying health conditions and remains hospitalized.
The affected person has a mixed backyard flock of domestic poultry at home that had exposure to wild birds.
The domestic poultry or wild birds are the most likely source of virus exposure; however, public health investigation is ongoing.
The Washington State Department of Health is working with the local health department and the Washington State Department of Agriculture to complete exposure and animal health investigations.
Public health disease experts have not identified any increased risk to the public.
(...)
Source: Department of Health, State of Washington, https://doh.wa.gov/newsroom/h5n5-avian-influenza-confirmed-grays-harbor-county-resident
____
I am an Italian blogger, active since 2005 with main focus on emerging infectious diseases such as avian influenza, SARS, antibiotics resistance, and many other global Health issues. Other fields of interest are: climate change, global warming, geological and biological sciences. My activity consists mainly in collection and analysis of news, public services updates, confronting sources and making decision about what are the 'signals' of an impending crisis (an outbreak, for example). When a signal is detected, I follow traces during the entire course of an event. I started in 2005 my blog ''A TIME'S MEMORY'', now with more than 40,000 posts and 3 millions of web interactions. Subsequently I added an Italian Language blog, then discontinued because of very low traffic and interest. I contributed for seven years to a public forum (FluTrackers.com) in the midst of the Ebola epidemic in West Africa in 2014, I left the site to continue alone my data tracking job.
Human Avian Influenza Cases in Washington State Residents{*}
[Exposure - Probable - Confirmed - Total human cases (H5)]
-- Poultry - 3 - 11 - 14
-- Unknown- 1{^} - 0 - 1
-- Total - 15
{*} Washington residency could not be confirmed for one case with exposure to poultry in Washington.
{^} Currently under investigation; case classification and source of infection may be updated.
Note: Updates to national public health reporting and notification of novel influenza A infections were approved by the Council of State and Territorial Epidemiologists (CSTE) in June 2024 and enacted in September 2024. Whether a case is counted as confirmed or probable is determined after completion of a public health case investigation and takes into account a person's exposure to avian influenza virus, whether confirmatory testing at the CDC was negative or positive, and whether a person experienced symptoms of illness. The specific criteria used to determine if a case is confirmed, or probable is based on a standardized case definition for public health surveillance which allows states to apply the same criteria and to count cases in the same manner for national reporting.
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Source: Department of Health, State of Washington, https://doh.wa.gov/you-and-your-family/illness-and-disease-z/avian-influenza
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I am an Italian blogger, active since 2005 with main focus on emerging infectious diseases such as avian influenza, SARS, antibiotics resistance, and many other global Health issues. Other fields of interest are: climate change, global warming, geological and biological sciences. My activity consists mainly in collection and analysis of news, public services updates, confronting sources and making decision about what are the 'signals' of an impending crisis (an outbreak, for example). When a signal is detected, I follow traces during the entire course of an event. I started in 2005 my blog ''A TIME'S MEMORY'', now with more than 40,000 posts and 3 millions of web interactions. Subsequently I added an Italian Language blog, then discontinued because of very low traffic and interest. I contributed for seven years to a public forum (FluTrackers.com) in the midst of the Ebola epidemic in West Africa in 2014, I left the site to continue alone my data tracking job.
For immediate release: November 13, 2025 (25-136)
Contact: DOH Communications
If confirmed, this would be the first human case of avian influenza reported in Washington in 2025
OLYMPIA – A Grays Harbor County resident has tested preliminarily positive for avian influenza, also known as bird flu. Confirmatory testing through the Washington State Public Health Laboratories is pending.
Health officials are working to determine the potential sources of the infection, including contact with wild or domestic birds.
The person, who is an older adult with underlying health conditions, developed a high fever, confusion, and respiratory distress and was hospitalized in early November.
They are currently receiving treatment in King County after previously being treated in Thurston and Grays Harbor counties.
Public health disease experts have not identified any risk to the public. The Washington State Department of Health is working with the local health departments and healthcare facilities to support the investigation.
About Avian Influenza
Avian influenza is a disease caused by influenza type A viruses, which naturally occur in wild aquatic birds around the world. These viruses can infect other bird species, and, occasionally mammals, and can be deadly to domestic birds such as chickens and turkeys. On rare occasions, avian influenza viruses can infect people and make them sick. Most cases have occurred in people who were exposed to sick or infected animals. Reported human cases of avian influenza in the United States have typically been mild, with symptoms such as conjunctivitis (red eyes), fever, and respiratory symptoms.
The risk of avian influenza increases in the fall and winter because migratory birds can carry the virus and spread it to domestic animals including commercial poultry farms and backyard flocks.
Transmission of avian influenza between humans is extremely rare and has never been documented in the United States. To ensure that human-to-human spread is not occurring, public health officials are contacting anyone who has been in close contact with the patient to monitor for symptoms and provide testing and treatment as needed.
Public Health Guidance
The Centers for Disease Control and Prevention (CDC) currently considers the risk to the public from avian influenza to be low. However, people who work with or have recreational contact with infected birds, cattle, or other potentially infected domestic or wild animals, are at higher risk and should take precautions, including wearing personal protective equipment (PPE) such as gloves, masks, eye protection, and fluid-resistant coveralls or other outerwear.
People with backyard poultry should avoid contact with sick or dead birds and report illness to the Washington State Department of Agriculture (WSDA) by calling 1-800-606-3056 or reporting online. Veterinarians should report sick or dead domestic animals or livestock suspected of having avian influenza to WSDA. Avoid contact with sick or dead wildlife and report sick or dead wild birds or other animals to the Washington State Department of Fish & Wildlife. Never handle or allow pets near dead birds or other wildlife.
Avoid eating raw or undercooked food products, such as unpasteurized (raw) milk or raw cheeses, and don’t feed these products to pets.
It is especially important that people who may have exposure to sick birds get a seasonal flu vaccine. While the seasonal flu vaccine will not prevent bird flu infection, it reduces the risk of becoming sick with both human and avian influenza viruses at the same time. Seasonal flu vaccine is recommended for everyone six months and older.
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Source: Department of Health, State of Washington, https://doh.wa.gov/newsroom/grays-harbor-county-resident-tests-preliminarily-positive-avian-influenza
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I am an Italian blogger, active since 2005 with main focus on emerging infectious diseases such as avian influenza, SARS, antibiotics resistance, and many other global Health issues. Other fields of interest are: climate change, global warming, geological and biological sciences. My activity consists mainly in collection and analysis of news, public services updates, confronting sources and making decision about what are the 'signals' of an impending crisis (an outbreak, for example). When a signal is detected, I follow traces during the entire course of an event. I started in 2005 my blog ''A TIME'S MEMORY'', now with more than 40,000 posts and 3 millions of web interactions. Subsequently I added an Italian Language blog, then discontinued because of very low traffic and interest. I contributed for seven years to a public forum (FluTrackers.com) in the midst of the Ebola epidemic in West Africa in 2014, I left the site to continue alone my data tracking job.
