Michigan dairy worker is second human bird flu case linked to cows
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Key takeaways:
- A dairy worker in Michigan is the second confirmed human case in the current bird flu outbreak.
- The CDC said it still considers the threat of bird flu to humans to be low.
A dairy worker in Michigan became the second human case of highly pathogenic avian influenza virus linked to an outbreak in dairy cows, the CDC and Michigan health officials announced Wednesday.
The CDC said the threat to humans from influenza A(H5N1) — also known as “bird flu” — remains low.
Although H5N1 has been identified in more U.S. dairy herds in the last few weeks, just one previous human case linked to the outbreak had been confirmed, in a Texas dairy worker — thought to be the first mammal-to-human transmission of H5N1.
“As with the case in Texas, the individual is a worker on a dairy farm where H5N1 virus has been identified in cows,” the CDC said in a press release.
They are only the second and third people in the U.S. to ever test positive for H5N1. The first case occurred in 2022 in a Colorado worker who culled poultry presumed to be infected with the virus.
Currently, the U.S. Department of Agriculture has identified 52 dairy herds in nine states with H5N1 circulating among cattle. The states are Colorado, Idaho, Kansas, Michigan, New Mexico, North Carolina, Ohio, South Dakota and Texas.
In addition to working with famers, the USDA and other state and local health agencies, the CDC said it has been monitoring influenza A surveillance systems for spikes in influenza A virus, which could help identify potential H5N1 cases.
Local health officials took an upper respiratory tract specimen from the Michigan worker’s nose, which tested negative for influenza, but also forwarded an eye specimen to the CDC for testing. The eye specimen tested positive for H5N1.
Like the worker in Texas, who had conjunctivitis, the dairy worker in Michigan reported only eye symptoms.
“Attempts to sequence the virus in the clinical specimen are underway,” the CDC said. “Additional genetic analysis will look for any changes to the virus that could alter the agency’s risk assessment.”
One such change would be evidence that the virus has undergone genetic changes that would make it more transmissible between humans, which scientists have not found.
The CDC continues to advise people avoid close, long or unprotected exposures to wild birds, poultry, cattle, animal excrement, raw milk or other materials or animals suspected or confirmed to have H5N1.
“Given the high levels of A(H5N1) virus in raw milk from infected cows, and the extent of the spread of this virus in dairy cows, similar additional human cases could be identified,” the CDC said. “Sporadic human infections with no ongoing spread will not change the CDC risk assessment for the U.S., which CDC considers to be low.”
References:
- CDC. Influenza (flu): H5N1 bird flu: Current situation summary. https://www.cdc.gov/flu/avianflu/avian-flu-summary.htm. Updated May 21, 2024. Accessed May 22, 2024.
- First case of influenza A (H5) detected in Michigan resident. https://www.michigan.gov/mdhhs/inside-mdhhs/newsroom/2024/05/22/influenza-a-detection. Published May 22, 2024. Accessed May 22, 2024.
- USDA. Highly pathogenic avian influenza (HPAI) detections in livestock. https://www.aphis.usda.gov/livestock-poultry-disease/avian/avian-influenza/hpai-detections/livestock. Updated May 22, 2024. Accessed. May 22, 2024.
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