A third person in the U.S. has been hospitalized due to avian influenza and one person has died as the virus continues to spread among poultry and dairy cattle. Experts have their eyes on the situation. And, under the right circumstances, a bird flu vaccine might become necessary, they say.
"The avian influenza situation is alarming simply because we see so much disease occurring in both birds and livestock." Dr. Stuart Ray, professor of medicine and oncology at Johns Hopkins University School of Medicine, tells TODAY.com.
"It is concerning," agrees Dr. Richard Martinello, Chief Medical Officer for Yale Medicine and an infectious diseases expert.
Since 2021, experts have seen bird flu — also called H5 influenza or highly pathogenic avian influenza (HPAI) — spreading "fairly quickly" across the wild and domestic bird populations and, now, among dairy cattle, Martinello tells TODAY.com.
While there have been "sporadic" infections among cows before, Ray says, they haven't been this widespread before. The first case in dairy cows in the U.S. was noted just last year. The virus has since been found in raw milk and raw pet food, leading to recalls and a risk of infection for pets, he adds.
"It's cropping up in a lot of places," Ray says, suggesting that the virus is "acquiring characteristics" and that it's "gained the ability to to get into mammalian hosts."
Every time someone gets sick with bird flu, that gives the virus "a chance to become better adapted to people and better adapted to spread from one person to another," Martinello says.
"And that's what can cause the next pandemic," he explains.
Is there a bird flu vaccine for chickens?
Just last week, the U.S. Department of Agriculture conditionally approved a vaccine to protect poultry from avian influenza.
Vaccinating poultry against bird flu is something that other countries have tried, Ray says. But the U.S. has generally opted to control the spread via a surveillance approach instead.
There's been some resistance to vaccinating birds in the past, Ray says, because vaccinated birds shed less virus if they get sick, masking the presence of the virus and making outbreaks harder to identify.
"But this situation is getting big enough that they realize the vaccination of birds may help preserve poultry flocks," he says.
Is there a bird flu vaccine for humans?
There are two H5 vaccines that have been developed and approved for use in humans, Martinello says. While those vaccines aren't available right now, they could be shipped out within weeks, if needed, health officials said in December.
These vaccines target past H5 variants, which are different from the versions of the virus currently circulating. There is "some thought" that the protection from those vaccines would be sufficient, Martinello says. But officials may also want to update the vaccines to target newer strains.
In that case, those vaccines "could be used as a template for this strain substitution, so that vaccine supply could be updated and rapidly scaled," Ray says. It would be a similar process to that of the seasonal flu vaccines, which are updated to target whichever strains are circulating that year, he says.
If the virus starts to spread among humans on a larger scale, we would need tens or even hundreds of millions of doses for the U.S. alone, Martinello says. Because of that huge scale, "my guess is ... instead of producing the old vaccine, they would want to use the mRNA technology to produce a vaccine," Martinello says.
In that case, with government support, Martinello says, "we would be very well positioned to have something available to people within a few months."
Multiple vaccines, including at least one mRNA vaccine candidate, are in development now.
Ultimately, experts have long hoped for a pan-influenza vaccine, which would target a part of the virus that changes less frequently or less dramatically, Ray explains. With that, "maybe we could have (a flu vaccine) that lasts for multiple seasons," he says.
When will a vaccine be necessary?
Avian influenza or bird flu is a disease that naturally spreads among wild aquatic birds worldwide, as well as domestic poultry and other bird and animal species.
While a bird flu vaccine rollout isn't necessary yet, the experts say, we may need it if certain conditions arise.
So far in this outbreak, there have been 68 human cases of bird flu in the U.S., according to the most recent data available from the Centers for Disease Control and Prevention. "Most people have experienced very limited conjunctivitis that's self-resolved," Martinello says, though there has been one death and a few cases of severe illness.
Most people who've gotten sick with bird flu in the current outbreak in the U.S. have had contact with infected animals, including farm animals and backyard flocks. In three cases, the source of exposure was unknown.
However, if there's evidence of sustained transmission from person to person, Ray says, that would be a serious warning sign that it's time for vaccines. That "would be the threshold," he says.
We don't know when or how quickly that might happen. "It might take years or it could take weeks," Ray says, "and it only has to happen once for it to become a much more widespread problem."
And a change in the virus like that — what experts call an antigenic shift — is often a "precedent for a pandemic," Ray says.
Other ways to protect yourself from bird flu
For most of the general public, bird flu isn't a major threat — but it's worth keeping an eye on, the experts say.
Most people "don't need to worry or change what they're doing in their in their day to day," Martinello says. "But this is something we should all be concerned about and paying a degree of attention to."
Bird flu is already causing major disruptions for farms and massive increases to the price of eggs. To avoid bird flu, it's important to avoid drinking raw milk, to cook your eggs properly before eating them and to not give your pets raw food.
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