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 36 people in the United States. Fifteen of these cases were associated with exposure to H5N1 bird flu-infected poultry and 20 were associated with exposure to sick or infected dairy cows12. 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 36 cases include 16 cases in California, three of which were confirmed last week. CDC also confirmed six human cases of H5 bird flu in poultry farm workers in Washington state last week. These are the first cases of H5 bird flu in Washington. Testing of additional specimens from Washington is ongoing. 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 cases 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.