FDA Preparing for Possible Bird Flu Spread Among Humans: Commissioner

Food and Drug Administration Commissioner Dr. Robert Califf in Washington in a file image. Joe Raedle/Getty Images

The U.S. Food and Drug Administration (FDA) is preparing for a scenario in which the highly pathogenic avian influenza starts spreading among humans, the agency’s commissioner said on May 8.

“This virus, like all viruses, is mutating. We need to continue to prepare for the possibility that it might jump to humans,” Dr. Robert Califf, the commissioner, told senators during a hearing in Washington.

The influenza, also known as the bird flu or H5N1, has recently started spreading among cattle and other species. One person in Texas has had a confirmed case this year.

So far, genetic sequencing and other data indicate that influenza poses little risk to people, and there are no signs that the flu is transmitting from person-to-person, according to U.S. officials. But they are working on getting treatments, tests, and vaccines ready in case that changes.

“We’ve been busy getting prepared for if the virus does mutate in a way that jumps into humans on a larger level,” Dr. Califf told the Senate Appropriations Committee’s Agriculture Appropriations Subcommittee.

The patient in Texas primarily experienced one symptom: inflamed eyes. Neither the patient nor many of the cows that have been infected have suffered respiratory symptoms. H5N1 commonly infects the respiratory tracts of birds.

“The real worry is that it will jump to the human lungs, where, when that has happened in other parts of the world for brief outbreaks, the mortality rates have been 25 percent,” Dr. Califf said. The worry is based in part on how viruses typically mutate, such as in the case of COVID-19.

From 2003 to April 1, 2024, 889 cases of H5N1 have been confirmed across the globe, according to the World Health Organization (WHO). Of the patients, 52 percent have died.

WHO chief scientist Jeremy Farrar said recently that H5N1 has developed into a “global zoonotic animal pandemic” and that scientists are concerned that the virus could evolve to spread among humans.

Tedros Ghebreyesus, the director-general of the organization, said Wednesday that “the virus does not show signs of having adapted to spread among humans, but more surveillance is needed.”

Many experts consulted by the U.S. government are concerned about the jump of the influenza to cattle and other species and how cattle intermingle with pigs, chickens, and humans on farms, according to Dr. Califf. A May 3 study from U.S. and Danish researchers said testing of tissues from cattle indicated the animals could serve as a “mixing vessel” for avian influenza because receptors from chickens, ducks, and humans were expressed in the cows.

While the risk is still low, “if we institute the countermeasures now and reduce the spread of the virus now, then we’re much less likely to see a mutation that jumps to humans for which we’re ill-prepared,” Dr. Califf added.

Current U.S. rules mandate testing of some cattle before being moved to another state. The guidance includes advising workers on farms to wear protective equipment when dealing with animals that may be or are sick with the bird flu.

The FDA is focusing in part on ensuring the country’s milk supply is safe to drink. The agency and its partners have tested samples of milk from grocery stores. Although some samples tested positive, no live virus has been detected, meaning the milk supply is safe, according to the agency.

Test results from beef have also found beef is safe, according to the U.S. Department of Agriculture.

The agency has confirmed H5N1 infections in 36 herds across nine states, including Colorado, Kansas, and Michigan. Data from affected cows indicate H5N1 began circulating in cattle in late 2023, according to a preprint paper from the department.

About 70 farm workers are being monitored in Colorado, officials said in a briefing this week, but none have displayed symptoms as of yet.