Avian Flu Infects Person Exposed to Sick Cows in Texas

Current H5N1 Clade Can Cause a Range of Illnesses
Past experience with H5N1 suggests that people who have contact with sick animals are at highest risk.  The CDC and its state partners routinely monitor people exposed to the virus, and from January 2022 through September 2023—a period when the US poultry industry was hit hard by the virus—had monitored about 6,500 people from 52 jurisdictions.

Of those, illnesses were reported in 165 people, and of those, testing revealed H5N1 in only 1, a person who was involved with culling at a poultry farm in Colorado. Fatigue was the man’s only symptom. Asymptomatic cases were reported in a few poultry workers in the United Kingdom and Spain who were positive for H5N1 in initial tests, and it’s not clear if their results reflected true infection or surface contamination of the upper airway tract.

The H5N1 clade circulating in the United States and several parts of the world, however, has resulted in severe and fatal infections. Globally, at least 12 cases involving the H5N1 clade have been reported, according to CDC background data. The disease was fatal in a patient in China, and Chileans and Ecuadorians had critical illnesses. Nearly all had been exposed to sick or dead birds.

An older H5N1 clade circulating in parts of Asia has been linked to a spate of recent H5N1 infections in Cambodia, most of which were severe or fatal. The cases typically involved people who had exposure to sick poultry.

Federal and state officials in the United States emphasize that the overall risk to the public is very low. With strong safeguards in place for the commercial milk supply, including routine pasteurization, they have repeated their longstanding assertion that raw milk can harbor pathogens and pose serious health risks to consumers.

Michigan Findings Add Evidence of Cow-to-Cow Spread
APHIS said the Michigan dairy herd had recently received cows from Texas, where the virus had already been confirmed. “Spread of symptoms among the Michigan herd also indicates that HPAI transmission between cattle cannot be ruled out,” the group said. Similarly, Idaho’s agriculture department last week announced that HPAI was detected at a facility that had imported cattle from an earlier-affected state.

The Michigan Department of Agriculture and Rural Development said the dairy herd where HPAI was found is in Montcalm County, which is in the central part of the state. The cattle were moved from Texas before any animals on the source farm showed signs of disease, and they didn’t have any symptoms or appear ill when they were moved to Michigan.

Genetic sequencing suggests that the H5N1 virus found in Michigan is very similar to strains confirmed in Texas and Kansas and was probably initially introduced to the dairy herds by wild birds, according to APHIS. So far, sequencing shows no changes in the virus that would make it more transmissible to humans.

Lisa Schnirring is news editor at CIDRAP. This article is published courtesy of the University of Minnesota’s Center for Infectious Diseases Research and Policy (CIDRAP).