Key warning signs about bird flu are all going in the wrong direction

Key warning signs about bird flu are all going in the wrong direction

Cows are milked at Cornell University in Ithaca, N.Y., on Dec. 11. The Agriculture Department this month issued an order requiring testing of the nation’s milk supply.

The simmering threat of bird flu may be inching closer to boiling over.

This year has been marked by a series of concerning developments in the virus’ spread. Since April, at least 65 people have tested positive for the virus — the first U.S. cases other than a single infection in 2022. Dairy cow herds in 16 states have been infected this year. The Centers for Disease Control and Prevention confirmed the country’s first severe bird flu infection on Wednesday, a critically ill patient in Louisiana. And California Gov. Gavin Newsom declared a state of emergency last week in response to rampant outbreaks in cows and poultry.

“The traffic light is changing from green to amber,” said Dr. Peter Chin-Hong, a professor of medicine at the University of California, San Francisco, who studies infectious diseases. “So many signs are going in the wrong direction.”

No bird flu transmission between humans has been documented, and the CDC maintains that the immediate risk to public health is low. But scientists are increasingly worried, based on four key signals.

For one, the bird flu virus — known as H5N1 — has spread uncontrolled in animals, including cows frequently in contact with people. Additionally, detections in wastewater show the virus is leaving a wide-ranging imprint, and not just in farm animals.

Then there are several cases in humans where no source of infection has been identified, as well as research about the pathogen’s evolution, which has shown that the virus is evolving to better fit human receptors and that it will take fewer mutations to spread among people.

Together, experts say, these indicators suggest the virus has taken steps toward becoming the next pandemic.

“We’re in a very precarious situation right now,” said Scott Hensley, a professor of microbiology at the University of Pennsylvania.

Since this avian flu outbreak began in 2022, the virus has become widespread in wild birds, commercial poultry and wild mammals like sea lions, foxes and black bears. More than 125 million poultry birds have died of infections or been culled in the U.S., according to the U.S. Agriculture Department.

About 125 million poultry birds have succumbed to the virus or been culled since 2022.

An unwelcome surprise arrived in March, when dairy cows began to fall ill, eat less feed and produce discolored milk.

Research showed the virus was spreading rapidly and efficiently between cows, likely through raw milk, since infected cows shed large amounts of the virus through their mammary glands. Raccoons and farm cats appeared to get sick by drinking raw milk, too.