Four reasons to be concerned (but not freak out) about the bird flu

Even as several federal agencies scheduled a Wednesday news conference to explain steps being taken to monitor and contain bird flu in the U.S., public health officials this week said even more vigilance is needed.

Now is the time to get ahead of bird flu, a handful of experts said, so we don't end up with another nightmare scenario.

"Every moment we're not preparing for it, is a failure on our part," said Dr. Nahid Bhadelia, an infectious disease specialist and founding director of Boston University's Center on Emerging Infectious Diseases. "It is always later than we think it is in an outbreak."

Bird flu is the nonscientific name for avian influenza, a type of flu virus that commonly infects waterfowl, turkeys and other birds. If it stays in birds, the main danger is to poultry. Flocks of chickens have had to be killed and eggs destroyed.

The larger concern is that it might evolve to become easily transmitted person-to-person. Bird flu is considered more dangerous than the annual flu because it's a strain humans have never encountered and it's likely to be highly contagious.

This probably hasn't happened yet, experts say.

"There's no current evidence of sustained human-to-human transmission," said Dr. Raj Panjabi, a part-time faculty member at Harvard Medical School and the former White House senior director for global health security and biodefense on the United States National Security Council.

"It's the moment to get ready to step up investments in public health, especially around prevention, protection and preparedness," Panjabi said.

Federal officials Wednesday said the latest round of testing proves the commercial milk supply is safe, as are products like cottage cheese and sour cream that are made from milk. They continue to test people who work on farms and only one person is known to have caught the virus in recent months. Vaccines and antivirals should be available if bird flu becomes transmissible from person to person.

But public health officials say they suspect more people have caught the virus from animals than we're aware of, and the chance of a bird flu pandemic cannot be ruled out.

Bhadelia said the absence of more human infections so far may reflect a lack of testing rather than a lack of actual infections.

"If I were a betting person, I would say there have probably been more human infections than what we've detected already in this country," she said. "I would bet part of my retirement on that."

In interviews this week, she and other leading epidemiologists, infectious disease, public policy and dairy industry experts, outlined four major concerns about bird flu, and one area where they feel mostly reassured:

It's called 'bird flu' but it's now in cows and other animals

What makes the outbreak so concerning is that the bird flu virus already has jumped from birds to other animals, including cows.

This form of avian influenza, a strain called H5N1, has been around since at least 1997, but it mutated a few years ago to become adaptable to more kinds of bird species as well as to mammals. Since then, it's been found in a range of animals, including a bottlenose dolphin off the coast of Florida in March 2022 and 29 house cats in Poland in June 2023.

But finding it on American cattle farms in early February was still a surprise, said Gerry Parker, associate dean for Global One Health at the College of Veterinary Medicine & Biomedical Sciences at Texas A&M University. Cows are not considered especially vulnerable to flu.

A virus that can thrive in a range of mammals might thrive in humans.

"The probability is going up that we might get a genetic reassortment that could turn this into a human virus," Parker said. "We don't know that, but as this continues to circulate into more mammalian species, the likelihood just increases. It may never happen but if it did, it could easily become a potential pandemic threat."

Do we really know where it's spread?

Bird flu initially struck a single dairy farm in the Texas panhandle and spread to other dairy farms from there, Dr. Rosemary Sifford, chief veterinary officer with the Department of Agriculture, told reporters Wednesday.

But it's still not clear exactly where the flu virus has spread or what it's capable of, said several experts, including Jennifer Nuzzo, a professor of epidemiology and director of the Pandemic Center at the Brown University School of Public Health.

"Our surveillance is inadequate to know where this virus is and where it isn't, which is critical for protecting farmworkers and people involved in the dairy industry ? but also important for staying ahead of this virus to prevent a future pandemic," Nuzzo said.

About 100 people working on dairy and cattle farms have been tested for active infections. Nuzzo and others said testing should be more widespread and should also include tests to see whether some had already recovered from infections.

"If there are a lot more people infected who aren't sick enough to go to the hospital, that would be important to know," Nuzzo said. "We have to have a much stronger conversation about how to improve our surveillance."

It's also unclear exactly how this virus is being transmitted among animals, which is crucial information for slowing or stopping the spread and protecting people working on farms.

Although flu is typically a respiratory virus passed through the air and by touching contaminated surfaces, it has behaved differently among cows; at least some of the transmission appears to be through unpasteurized milk. Farm cats have contracted the virus, potentially by drinking this milk.

"We think milk is the primary vector for movement (of the virus)," Sifford told reporters.

Milking equipment is cleaned but not sterilized between cows, Parker said, so the virus may be transmitted when one cow with the virus in her milk leaves some of it on the machine to be picked up by the next cow's udder.

The cows also passed it back to birds. Eight poultry flocks located near infected dairy herds contracted the virus after the cows did, though how they got it remains unclear.

No one knows how sick a person might get if they catch H5N1.

Birds often die; most cows, so far, have recovered from their infections, said Jamie Jonker, chief science officer of the National Milk Producers Federation.

The one farmworker in Texas who caught bird flu only suffered from an eye infection and apparently recovered fully. Bhadelia speculated he might have caught it by touching his eye after touching contaminated milking equipment, which is why the infection was focused on his eye.

Since 1997, about half the people hospitalized globally with bird flu have died. But Bhadelia said many more might have caught the virus from direct interactions with infected birds and never showed symptoms or were so mildly ill that they never required treatment ? so the actual death rate is unknown. Plus, if the virus did adapt to become transmissible in people, it might become milder, though we can't count on that, she said.

In any kind of emerging crisis, there's never enough data, Parker said. "I call it the fog of war," he said.

Workers may not be adequately protected

Although the average American is not at risk right from bird flu, farmworkers, especially those working around poultry and cattle, probably are.

"We've been so fixated on, 'Is this going to become a pandemic?' and not enough on 'There's a threat on our farms today,'" Nuzzo said. "We should not wait for a severe illness in order to protect farmworkers."

The Centers for Disease Control and Prevention recently recommended dairy workers and people who come onto dairy farms use eye protection, wash their hands frequently and wear things like disposable coveralls if they travel from farm to farm, so as not to carry the virus with them, Jonker noted.

In addition to the basic worries about worker health, the more workers become infected, the greater the risk one of them won't be able to clear the virus quickly. Viruses evolve as they pass from person to person but also within a single person, especially if they don't shake it off quickly, Bhadelia said.

"The more people it infects, and the longer it adapts to the human body," she said, the more likely the virus will become contagious ? and dangerous ? to other people.

Yes, there are vaccines and antivirals, but...

Unfortunately, even people who've gotten annual flu shots or caught the flu recently won't have any protection against the H5N1 strain, said Lawrence Gostin, a leader in global health at Georgetown University, where he is faculty director of the O’Neill Institute for National and Global Health Law.

The federal government has flu vaccine and antiviral stockpiles that theoretically could be useful if H5N1 becomes easily transmissible among people.

But public health experts say the reality is much more complicated.

There won't be enough for everyone and the vaccine that's been stockpiled hasn't been tested to prove it can effectively prevent infection or severe disease.

"I don't know that anyone has a vaccine that's been tested thoroughly that anyone would be really confident about its effectiveness," said Dr. Jeremy Luban, a professor at the UMass Chan Medical School and member of the executive committee of the Massachusetts Consortium on Pathogen Readiness. "Part of the problem is we don't actually know what that virus is until it appears."

Two companies are testing a candidate vaccine in early trials, David Boucher, a top official within the Administration for Strategic Preparedness and Response, said at the news conference.

If the virus moves from animals into people, it will continue to mutate, so existing vaccines might not be effective and it's challenging to develop and test a vaccine against a virus that does not yet exist, Luban said.

Such testing would take time and the flu virus, which mutates much faster than the virus that causes COVID-19, would continue to transform.

Antivirals, like Tamiflu, are likely to be effective against bird flu, federal officials say.

But they need to be taken within the first day or two after infection starts, at a time when most people aren't even sure whether they are sick and well before they have time to make a doctor's appointment and get and fulfill a prescription for an antiviral.

But the food supply is almost certainly safe

Both public health and federal officials reassured the public about the safety of the commercial food supply.

Concerns about bird flu passing through milk is another reason people should avoid drinking unpasteurized milk, Nuzzo said.

"There are a lot of reasons not to drink raw milk," she said. "We just added a new one."

The point of pasteurization is to kill pathogens. The Food and Drug Administration has tested 297 commercial samples that had evidence of the H5N1 virus, including 96 milk samples and another 200 products made with milk, like cottage cheese and sour cream. In all cases, the virus had been killed by pasteurization and posed no health risk, said Dr. Donald A. Prater, the FDA's acting director of the Center for Food Safety and Applied Nutrition.

The agency also tested infant and toddler formula and found no viral particles at all, Prater told reporters.

Surveillance on poultry farms is more extensive than on cattle farms because bird flu has been seen in birds for much longer, Jonker and others said. At the first sign of infection on an egg or chicken farm, animals are "culled," a polite way of saying "killed" and their eggs destroyed. The government long ago set aside funds to compensate farmers for having to take such drastic actions, he said.

The meat supply is almost certainly safe, Emilio Esteban USDA's Under Secretary for Food Safety, told reporters.

He said animals are inspected before slaughter and carcasses must pass inspection after slaughter. "We are confident the meat supply is safe," he said.

For extra security, his department is now running tests on retail samples of ground beef purchased from states where dairy herds have been affected by bird flu, along with muscle from cows killed after being infected with bird flu and from beef patties cooked at three different temperatures to document that cooking kills any virus that might remain in the meat.

"We are pretty sure that the meat supply is safe," he said. "We are doing this just to enhance our scientific knowledge, to make sure we have additional data points.

This article originally appeared on USA TODAY: Bird flu is worth worrying about, but not freaking out about. Yet.