Milk Tests Suggest Bird Flu Outbreak Has Spread Widely

Bird flu has been confirmed in 33 dairy herds in eight states, officials say, but the results of a nationwide Food and Drug Administration analysis suggest the virus is far more widespread. In an update Thursday, the agency said inactive fragments of the virus were found in one in five samples of retail milk in the nationally representative study. Regulators say there's no sign that there is a risk to consumers or that the virus remained active after pasteurization, but officials are continuing to test milk samples for live virus, the New York Times reports.

• Is it safe? "To date, the retail milk studies have shown no results that would change our assessment that the commercial milk supply is safe," the FDA said. The agency said it has not found any cases of H5N1 in humans "beyond the one known case related to direct contact with infected cattle."

• How long the virus has been spreading. Michael Worobey, an evolutionary biologist with the University of Arizona, says genetic data released by the USDA suggests the virus spread from birds to cows late last year, the AP reports. He says the virus spread among cattle, possibly through equipment like milking machines, and cows spread it back to birds. "The genetic evidence is as clear as could be," Worobey says. "Birds that are sampled on these farms have viruses with clear mammalian adaptations."
• Testing. Earlier this week, the USDA said dairy cows need to be tested for the virus before they can cross state lines. Before that, testing was voluntary, though scientists have been urging authorities to step up testing to determine how big the outbreak is. The Times notes that if it continues to spread among herds, the virus will have "opportunities to acquire mutations that make it more transmissible among humans."
• How farms are responding. Dairy farmers have started banning visitors and chopping down trees to keep birds away, reports Reuters. "Think of our farm now as a gated community for cows," says North Carolina dairy farmer Karen Jordan.
• Echoes of 2020? Experts say the response to the outbreak has echoes of the early days of the COVID pandemic, according to the Washington Post. Providing timely updates on how the virus is spreading requires coordination among multiple agencies, which "doesn't seem to be happening due to different cultures, priorities, legal responsibilities, scientific expertise, and agility," says epidemiologist Katelyn Jetelina. "Mix that in with the usual challenges of scientific uncertainty, complexity and, quite frankly global pressure, and you got yourself an utterly, unacceptable mess." Worobey says this is the kind of outbreak "that we were hoping, after COVID, would not go unnoticed. But it has."

(More bird flu stories.)