CDC confirms second human case of H5 bird flu in Michigan; Third case linked to dairy outbreak | CDC Online Newsroom

May 30, 2024 – A second human case of infection with the highly pathogenic avian influenza (HPAI) A(H5) virus has been identified in the state of Michigan. This is the third human case associated with an ongoing multistate outbreak of A(H5N1) virus in dairy cows in the United States. None of the three cases is associated with the others. As with the previous two cases (one in Texas, one in Michigan), the person is a dairy farm worker exposed to infected cows, making this another example of likely cow-to-cow spread. . This is the first human case of H5 in the United States reporting symptoms more typical of acute respiratory illness associated with influenza virus infection, including A(H5N1). The CDC continues to closely monitor available data from flu surveillance systems, particularly in affected states, and there have been no signs of unusual flu activity in people, including no increase in visits in emergency rooms for influenza and no increase in laboratory detection of human influenza cases.

Based on the information available at this time, this case does not change the CDC’s current assessment of the human health risks of avian influenza A(H5N1) to the general American public, as the three sporadic cases occurred direct contact with infected cows. Risk depends on exposure and, in this case, the relevant exposure is to infected animals. The risk to members of the general public who are not exposed to infected animals remains low. However, this development highlights the importance of recommended precautions in people exposed to infected or potentially infected animals. People with close or prolonged, unprotected exposure to infected birds or other animals (including livestock), or to environments contaminated with infected birds or other animals, are at greater risk of infection and should take precautions.

Background of the case

A dairy worker who was exposed to H5N1-infected cows (on a different farm than last week) reported his symptoms to local health authorities. The patient reported upper respiratory symptoms including cough without fever and eye discomfort with watery discharge. The patient received antiviral treatment with oseltamivir, is isolating at home, and his symptoms are resolving. The patient’s household contacts have not developed any symptoms, are under medical surveillance and have been offered oseltamivir. No other workers on the same farm have reported symptoms and all staff are being monitored. There is currently no indication of human-to-human spread of the A(H5N1) virus.

Samples were taken from the patient; one of whom tested positive for influenza A(H5) virus using the CDC test performed at the state health department laboratory. The specimens were sent to the CDC for further testing. They were received on May 29 and test results that night confirmed infection with the A(H5) virus. Michigan was later informed of the results.

The influenza virus neuraminidase designation (the N in the subtype) is awaiting genetic sequencing at the CDC and results will be available within 1-2 days, if successful. Additional genetic analysis will look for any changes in the virus that could change the agency’s risk assessment.

CDC Activities and Risk Assessment

This case was detected through Michigan’s active surveillance program for people exposed to infected livestock, in collaboration with the CDC. The identification of an additional case of H5 is not surprising and demonstrates the importance of a proactive public health response. Given the extent to which this virus has spread among dairy cows, additional human cases in people at higher risk would not be surprising. One of the CDC’s current priorities is to prevent new cases of A(H5N1) virus infections among dairy herd workers, who are at higher risk of exposure. The CDC previously provided updated interim recommendations for worker protection to include those who work with dairy cows and directed states to provide personal protective equipment to agricultural workers. Additionally, the agency conducts ongoing outreach to groups representing agricultural workers.

CDC Recommendations

• People should wear recommended personal protective equipment when interacting with infected or potentially infected animals and monitor their health for 10 days after their most recent exposure. Learn more about CDC recommendations for worker protection and the use of personal protective equipment (PPE).
• People should avoid close, prolonged, or unprotected exposure to sick or dead animals, including wild birds, poultry, other domestic birds, and other wild or domesticated animals (including cows).
• People should also avoid unprotected exposure to animal feces, bedding (litter), unpasteurized (“raw”) milk, or materials that have been touched by or near birds or other animals suspected or confirmed of the A(H5N1) virus.

More information is available on the CDC website at H5N1 Avian Influenza: Current Situation Summary.