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Technical Report: Highly Pathogenic Avian Influenza A(H5N1) Viruses - Updated March 17, 2023

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  • Technical Report: Highly Pathogenic Avian Influenza A(H5N1) Viruses - Updated March 17, 2023

    Updated March 17, 2023

    Key Points
    • CDC is actively working on the domestic situation with clade HPAI A(H5N1) viruses in wild birds and poultry outbreaks, including conducting surveillance among people with relevant exposures and preparing for the possibility that contemporary HPAI A(H5N1) viruses gain the ability for increased transmissibility to people.
    • CDC, along with our state and local public health partners, continues to actively monitor people in the United States who have been exposed to infected birds and poultry for 10 days after exposure. To date, more than 6,300 people in 52 jurisdictions have been monitored since 2022, and only one human case has been identified
    • An H5 candidate vaccine virus (CVV) produced by CDC is nearly identical or, in many samples, identical to the hemagglutinin (HA) protein of recently detected clade HPAI A(H5N1) viruses in birds and mammals (including the recent outbreak in farmed mink in Spain) and could be used to produce a vaccine for people, if needed, and would provide good protection against the clade HPAI A(H5N1) viruses circulating in birds. This H5 CVV is available and has been shared with vaccine manufacturers.
    • Because influenza viruses are constantly changing, CDC performs ongoing analyses of A(H5N1) viruses to identify genetic changes that might allow for spread more easily to and between people, cause serious illness in people, reduce susceptibility to antivirals, affect the sensitivity of diagnostic assays, or reduce neutralization of the virus by vaccine induced antibodies. To date, no such concerning changes have been identified in HPAI A(H5N1) viruses circulating in wild birds and poultry worldwide or that have sporadically infected humans.
    • Currently, HPAI A(H5N1) viruses are believed to pose a low risk to the health of the general public in the United States; however, people who have job-related or recreational exposures to infected birds may be at higher risk of infection and should take appropriate precautions outlined in CDC guidance.
    • Comprehensive surveillance and readiness efforts are ongoing, and CDC continually takes preparedness measures to be ready in case the risk to people from HPAI A(H5N1) or other novel influenza A viruses changes.