CDC Reports Fourth Human Case of H5 Bird Flu Tied to Dairy Cow Outbreak
A human case of highly pathogenic avian influenza (HPAI) A(H5) (“H5 bird flu”) virus infection in the United States has been identified in the state of Colorado. This is the fourth case associated with an ongoing multistate outbreak of A(H5N1) in dairy cows and the first in Colorado. Previous cases were reported in Texas (1) and Michigan (2). As with previous cases, the person is a worker on a dairy farm where cows tested positive for A(H5N1) virus. The person reported eye symptoms only, received oseltamivir treatment, and has recovered. CDC has been watching influenza surveillance systems closely, particularly in affected states, and there has been no sign of unusual influenza activity in people, including in syndromic surveillance.
Based on the information available at this time, this infection does not change CDC’s current H5N1 bird flu human health risk assessment for the U.S. general public, which the agency considers to be low. However, this development underscores the importance of recommended precautions in people with exposure to infected animals. People with close or prolonged, unprotected exposures to infected birds or other animals (including livestock), or to environments contaminated by infected birds or other animals, are at greater risk of infection.
Case Background
A dairy worker who was being monitored because of their work exposure to H5N1 virus-infected cattle reported symptoms to state health officials. Testing results were inconclusive at the state. Specimens forwarded to CDC for additional testing were positive for influenza A(H5). The state was then notified of the results. The designation of the influenza virus neuraminidase (the N in the subtype) is pending genetic sequencing at CDC. Attempts to sequence the virus in the clinical specimen are underway and will be made available within 1-2 days if successful. Additional genetic analysis will look for any changes to the virus that could alter the agency’s risk assessment.
