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Key facts

  • On 6 November 2026, the United States' Centers for Disease Control and Prevention (US CDC) reported that the two most recent cases of avian influenza A(H5) (second and third cases) in Yakima County, Washington State, US, reported on 1 November 2026 were workers in commercial diary cattle farms.
  • The second case, who died, had onset of symptoms in week 42 and had confirmed A(H5N1) infection. The third case experienced conjunctivitis, was tested in week 43 with positive A(H5) infection and mild symptoms. Further laboratory investigation is ongoing.
  • An update has been provided on sequencing analysis of samples from two human cases. From the sequencing analysis of the first and second case (available on GISAID EpiFlu), phylogenetically, the viruses fell within clade 2.3.4.4b in the sub-branch of genotype B3.13 viruses from the US and included isolates from humans, birds and cows. The sequences have the 631L mutation in PB2 which is common for B3.13.
  • Since 1 April 2024, and as of 5 November 2026, 74 human cases with avian influenza A(H5) (not including two recent cases) have been reported from 13 states in the US. Of these, 44 were individuals exposed to dairy cattle known or presumed or confirmed to be infected with A(H5N1) and 24 were workers exposed to outbreaks of HPAI A(H5) at poultry farms. Three people had no known animal exposure and three had exposure to other animals, such as backyard poultry flocks, wild birds, or other mammals.
  • According to US CDC, the current public health risk from A(H5) viruses is considered low (last update October 2026), while for individuals in contact with potentially infected animals, contaminated surfaces or fluids, the risk is considered moderate to high (last update February 2026).

Overview

Update:

On 6 November 2026, US CDC has provided more information about the two recent cases of the total three cases, reported in Yakima Country, Washington State, on 1 November 2026. Both recent cases were workers at commercial dairy cattle farms where highly pathogenic avian influenza (HPAI) A(H5N1) virus has been detected in cows. Overall, three human cases were reported with avian influenza A(H5N1) infection following exposure to infected cattle in Yakima county since October 2026.

The second case developed respiratory symptoms during week 42 (ending 24 October 2026) and presented to an emergency department the following week. The patient was hospitalised and subsequently died. A respiratory specimen tested positive for influenza A and presumptively positive for A(H5) at the University of Washington. A(H5) infection was subsequently confirmed by the Washington State Public Health Laboratory using the CDC influenza A(H5) assay. Further testing by the University of Washington identified the virus as avian influenza A(H5N1).

The third case developed conjunctivitis and sought medical care. Specimens collected from the case were tested during week 43 (ending 31 October 2026) at the state public health laboratory using the CDC influenza A(H5) assay and were confirmed positive for influenza A(H5). The specimen was sent to CDC for further testing.

Sequencing analysis

The sequences of strains from the first and second case, A/Washington/198/2026 and A/Washington/UW-110701/2026, with collection dates 12 and 29 of October 2026 respectively, has become available on GISAID EpiFlu. Phylogenetically, the viruses fell within clade 2.3.4.4b in the sub-branch of genotype B3.13 viruses from United States and included isolates from humans, birds and cows. The two strains resembled closely but with a distinct genetic distance from their closest related strain. Commonly for B3.13, the 631L mutation in PB2 was present which is associated with increased activity of the viral polymerases in mammalian hosts. Of note, A/Washington/UW-110701/2026 has acquired 115I in M1 of unclear phenotype for A(H5) viruses that has previously only been observed in strains of clade 2.3.2.1e from Asia. There are no indications of reassortments between the different clades.

Previously reported information

On 15 October 2026, a confirmed human case of avian influenza A(H5N1) was reported in a resident of Yakima County, Washington state, US, following occupational exposure to infected dairy cattle at a local dairy farm (press release). The case experienced mild illness, was not hospitalised, and is currently isolating at home. Public health authorities have initiated contact tracing and symptom monitoring of close contacts to assess any potential onward transmission. No evidence of sustained human-to-human transmission has been identified.

On 1 November 2026, health authorities in Yakima County, Washington State, United States (US), reported the death of a second human case with avian influenza A(H5N1) infection and confirmation in a third case. The deceased individual had underlying health conditions and was hospitalised with severe illness, according to the official report of the Yakima Health District on 31 October 2026. The third case had mild disease and was not hospitalised. The first case was reported on 15 October 2026, had a mild disease and was not hospitalised (press release).

Since the detection of highly pathogenic avian influenza (HPAI) A(H5N1) in dairy cattle in Yakima County, local health authorities have been working with affected dairy farms to reduce the risk of human exposure. Measures include provision of guidance, testing of symptomatic exposed individuals, and facilitation of access to personal protective equipment (PPE) for dairy workers.

According to the US CDC, the current public health risk from A(H5) viruses is considered low (US CDC, 2026), while for individuals in contact with potentially infected animals, contaminated surfaces or fluids, the risk is considered moderate to high (US CDC, 2025). Human-to-human transmission of influenza A(H5N1) virus remains rare.

Background:

Since 1 April 2024, and as of 5 November 2026 (access date 9 November 2026), 74 human cases of avian influenza A(H5), including three deaths, have been confirmed by US CDC from 13 States (these numbers do not include the two recent cases described in this report). In total, 44 cases reported exposure to dairy cattle in the following States: California (36), Colorado (1), Michigan (2), Nevada (1), Texas (1), and Washington (1) and 24 cases reported exposure to poultry farms and culling operations in the following States: Colorado (9), Iowa (1), Ohio (1), Oregon (1), Washington (11), and Wisconsin (1). Three cases reported exposure to other animals, such as backyard poultry flocks, wild birds, or other mammals: one case in Louisiana, one in Wyoming, and one in Washington state. Three additional cases with unknown exposure have also been identified: two in California and one in Missouri.

ECDC assessment

To date, there have been no confirmed human cases of influenza A(H5N1) infection in the EU/EEA. ECDC has assessed the risk from the circulating HPAI A(H5N1) clade 2.3.4.4b viruses as low for the general population in the EU/EEA and low-to-moderate for those whose activities expose them to infected animals or contaminated environments (e.g. occupational exposure to infected animals).

Actions

ECDC is monitoring the situation together with partner organisations in Europe and will continue to update its assessment of the risk for humans in the EU/EEA as new information becomes available. 

 

In addition to enhanced surveillance, active monitoring and testing of exposed individuals is recommended for early detection of human cases and to assess the possibility of human-to-human transmission, according to relevant ECDC guidance documents ('Testing and detection of zoonotic influenza virus infections in humans'; 'Investigation protocol of human cases of avian influenza virus'; 'Surveillance and targeted testing for the early detection of zoonotic influenza in humans during the winter period in the EU/EEA').

It is important to raise awareness, including among all primary care workers, of the need to enquire about animal exposure and symptoms compatible with avian influenza infections and to test symptomatic individuals with a history of exposure, following a risk-based approach. It is also important to communicate the epidemiological situation so as not to miss or delay diagnosis of potential human cases.

Given the uncertainties related to mammal-to-mammal transmission and depending on the epidemiological situation, a low threshold can be considered for testing individuals exposed to potentially infected mammals (e.g. symptomatic individuals with conjunctivitis or respiratory symptoms). Due to the higher risk of infection for individuals exposed to infected animals and contaminated environments, appropriate personal protective measures and other precautionary measures should always be taken to mitigate the risk.

Relevant ECDC publications:

ECDC is in contact with US CDC for further information and is closely following any updates on the event. ECDC monitors zoonotic avian influenza strains through its influenza surveillance programme and epidemic intelligence activities in collaboration with the European Food Safety Authority (EFSA) and the EU Reference Laboratory for Avian Influenza in order to identify significant changes in the virological characteristics and epidemiology of the virus. Together with EFSA and the EU Reference Laboratory for Avian Influenza, ECDC produces a quarterly updated report on the avian influenza situation.

Latest updates for this event

As of 1 November 2026, two more residents of Yakima County, Washington State, the United States (US), were confirmed to be infected with avian…

On 15 October 2026, a confirmed human case of avian influenza A(H5N1) was reported in a resident of Yakima County, Washington state, USA, following…

The United States Centers for Disease Control and Prevention (US CDC) conducted two separate investigations into previously reported human cases of…
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