The physical space of the MSK Library is permanently closed to visitors as of Friday, May 17, 2024. Please visit this guide for more information.
The physical space of the MSK Library is permanently closed to visitors as of Friday, May 17, 2024. Please visit this guide for more information.
Highly pathogenic avian influenza (HPAI) A(H5) viruses have been detected in U.S. wild aquatic birds, commercial poultry and backyard or hobbyist flocks beginning in January 2022. These are the first detections of HPAI A(H5) viruses in the U.S. since 2016. Preliminary genetic sequencing and RT-PCR testing on some virus specimens shows these viruses are HPAI A(H5N1) viruses from clade 2.3.4.4.
NOTE: On March 29, 2024 the CDC announced new interim recommendations for prevention, monitoring, and public health investigations of highly pathogenic avian influenza A(H5N1) virus in animals. Updates to this page are forthcoming.
| Dairy Cattle: On-going multi-state outbreak | Human Cases: 66 cases in the U.S. |
| Wild Birds: Widespread | Human Deaths: 1 death in the U.S. |
| Poultry Flocks: Sporadic outbreaks | Person-to-person spread: None |
| Mammals: Sporadic infections | Current public health risk: Low |
January 15 H5 Bird Flu Response: Focus Areas for Ongoing Public Health Risk Assessment
January 6 Information for Workers Exposed to H5N1 Bird Flu
December 26 Genetic Sequences of Highly Pathogenic Avian Influenza A(H5N1) Viruses Identified in a Person in Louisiana
The CDC provides updates on its response activities related to the multistate outbreak of avian influenza A(H5N1) virus, or "H5N1 bird flu," in dairy cows and other animals in the United States.
CDC continues to respond to the public health challenge posed by a multistate outbreak of avian influenza A(H5N1) virus, or "H5N1 bird flu," in dairy cows, poultry and other animals in the United States. CDC is working in collaboration with the U.S. Department of Agriculture (USDA), the Food and Drug Administration (FDA), Administration for Strategic Preparedness and Response (ASPR), state public health and animal health officials, and other partners using a One Health approach.
Since April 2024, CDC, working with state public health departments, has confirmed H5 bird flu infections in 44 people in the United States. Nineteen of these cases were associated with exposure to H5N1 bird flu-infected poultry and 24 were associated with exposure to sick or infected dairy cows [A][B]. The source of the exposure in one case, which was reported by Missouri on September 6, could not be determined. Serological testing of the contacts of the Missouri case have been reported, and that investigation has concluded.
The 44 cases include:
While these probable cases were negative on confirmatory testing at CDC, all four met the Council of State and Territorial Epidemiologists (CSTE) probable case definition and have been reported by the states.
Cases in California and Washington have occurred in workers on affected farms. All available data so far suggest sporadic instances of animal-to-human spread. The farm workers in California and Washington state all described mild symptoms, many with eye redness or discharge (conjunctivitis). Some workers who tested positive in Washington reported some mild upper respiratory symptoms. None of the workers were hospitalized. Updated case counts, including by state and source of exposure, are reflected in a table on CDC's website. To date, person-to-person spread of H5 bird flu has not been identified in the United States. CDC believes the immediate risk to the general public from H5 bird flu remains low, but people with exposure to infected animals are at higher risk of infection.
On the animal health side, since March 2024, USDA has confirmed infected cattle in 440 dairy herds in 15 U.S. states. The number of affected herds continues to grow nationally, with almost all new infections identified in herds in California. USDA reports that, since April 2024, there have been H5 detections in 45 commercial poultry flocks and 30 backyard flocks, for a total of 22.37 million birds affected.
These technical reports are intended for scientific audiences. Additional information for scientific audiences and the general public is available on CDC’s Information on Bird Flu webpage.
Technical Report: June 2024 Highly Pathogenic Avian Influenza A(H5N1) Viruses
This report provides an update to the April 26, 2024, report to include three additional sporadic human cases (1 in Australia and 2 in the United States) and recent activity in wild birds, poultry, and other animals, including the multi-state outbreak in U.S. dairy cattle, and updated information on monitoring for human infections with highly pathogenic avian influenza A(H5N1) virus infections in the United States.
CDC continues to believe that the overall risk to human health associated with the ongoing outbreaks of highly pathogenic avian influenza A(H5N1) viruses has not changed and remains low to the U.S. general public at this time.