A Texas dairy worker has tested positive for the highly pathogenic avian influenza (HPAI) H5N1, according to the CDC. The person inflicted has a mild case and is believed to be just the second human ever to have contracted the virus.
The news comes on the heels of USDA confirming detection of HPAI in seven dairy herds in Texas, two in Kansas, and one a piece in Idaho, Michigan, and New Mexico. The National Veterinary Services Laboratories is performing additional tests on presumptive positive results from Kansas, New Mexico, Ohio, and Texas.
“This infection does not change the H5N1 bird flu human health risk assessment for the U.S. general public, which CDC considers to be low,” USDA said in a statement.
Richard Webby, PhD, director of the World Health Organization Collaborating Centre for Studies on the Ecology of Influenza in Animals and Birds, and a virologist at St. Jude Children’s Research Hospital, tells Food Quality & Safety that dairy herd infections are extremely rare. “There were some hints of data that suggested cows could be sporadically infected with influenza A viruses, but many, including me, never thought of cows as likely hosts of the virus,” he says. “No one knows how the cows got infected and how it is moving between them now. There were reports of sick birds on the initial farms, but how the virus got from there to cows is unclear. If we can understand how the virus is moving, we can likely do many things to reduce the risk.”
He notes that this virus remains very much a bird virus, even after replicating in cows. As such, the risk to humans is low. “It is of course higher in those with close contact with the sick animals,” Dr. Webby adds. “Risk to the general population is very low, rock to workers is low, but certainly not zero, as highlighted by the one conjunctivitis case.”
A joint statement released by the National Milk Producers Federation, the International Dairy Foods Association, the U.S. Dairy Export Council, and Dairy Management Inc., noted that routine testing and well-established protocols for U.S. dairy will continue to ensure that only safe milk enters the food supply. “In keeping with the federal Grade A Pasteurized Milk Ordinance (PMO), milk from sick cows must be collected separately and is not allowed to enter the food supply chain,” the statement reads. “This means affected dairy cows are segregated, as is normal practice with any animal health concern, and their milk does not enter the food supply.”
Since 2022, HPAI has been detected in wild, commercial, and hobbyist bird flocks in more than 82 million birds across 48 states and 512 counties, according to the CDC.
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