AILSA CHANG, HOST:
Dairy cows in the U.S. are coming down with bird flu. Federal officials started investigating last month, and they found infected cows in more than 30 herds across eight states. And this week the FDA said that fragments of the virus are showing up in the milk supply. NPR's Pien Huang is here to explain. Hey, Pien.
PIEN HUANG, BYLINE: Hey, Ailsa.
CHANG: OK. So do we need to be freaking out right now about bird flu inside the milk supply? Like, what does this mean?
HUANG: OK, Ailsa, no and yes. Let me explain.
CHANG: OK.
HUANG: So this does not mean that the general public is at risk. Pasteurized milk at the grocery store is heated to kill germs. But what it does mean is that the outbreak of bird flu in dairy cows is bigger than officials had thought. So the Food and Drug Administration has been testing milk from the grocery store, and yesterday they announced that 20% of the samples they've tested so far have some traces of the bird flu virus. So finding that much of the virus this extensively in the food supply suggests that the H5N1 bird flu virus is infecting a lot more dairy cows than officials knew.
CHANG: Wow. When did they first find out that this was a problem?
HUANG: Well, even until last month, officials didn't even know that cows could get and spread the H5N1 bird flu virus. But this particular strain of bird flu is something that virus researchers have tracked in other animals for quite some time. It's considered highly pathogenic, very deadly to birds. And as far as researchers can tell, it first came to North America in 2021. Since then, it's been hitting poultry farms very hard. It's been spreading to other mammals as well, to dogs, cats, bears, skunks. Last year it caused a mass die-off of sea lions. But the fact that it's now infecting dairy cows and spreading between them raises new concerns for humans.
CHANG: Right. What about people? Like, has someone gotten sick from this already?
HUANG: Yeah. So far in this dairy cow outbreak, the CDC has confirmed one case of the bird flu in a dairy worker in Texas. It was a mild case. The worker got conjunctivitis, and that seemed to be about it. But Mary-Margaret Fill with the Tennessee Health Department says there are huge gaps in the surveillance. And she's heard about...
MARY-MARGARET FILL: Farmworkers with mild illness while they're working with cattle that are sick or increases in conjunctivitis or mild respiratory illness. That may be seen in some of those areas that we really just don't have visibility on.
HUANG: And Fill says that the official updated guidance for protecting farm workers, which the CDC updated today, recommends things like fit-tested respirator masks, which just isn't realistic on a lot of dairy farms. And officials also say that dairy farms haven't been super-welcoming to their outreach.
CHANG: Oh, that's interesting. OK. So what other measures is the government taking at this point?
HUANG: Well, the USDA has taken some actions. So starting on Monday, dairy cows have to test negative for H5N1 before they can cross state lines. That's to limit the spread of the virus. But the bigger concern, the pandemic concern, is whether the virus will turn into something that can easily infect humans, spread from person to person and make many people very sick.
CHANG: Exactly. So how is that concern being managed? Like, what's being done right now?
HUANG: Well, officials say that they've been stepping up their monitoring on cows and people. They've been trying to get more cows tested. They're looking at emergency room data for people every day. So far, they're not seeing signs of more serious human cases. But pandemic experts want to see more urgency. You know, bird flu variants caused at least three full-blown pandemics in the last century. And these experts say that monitoring should really be going beyond dairy cows right now to beef cattle, pigs, other farm animals and also wild animals as well.
CHANG: That is NPR's Pien Huang. Thank you so much, Pien.
HUANG: You're welcome. Transcript provided by NPR, Copyright NPR.
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