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Bird flu is still spreading in dairy cattle -- scientists are concerned

A MARTÍNEZ, BYLINE: Bird flu is still here, spreading in dairy cattle. And scientists say that recent news of a second human case underscores the need to stay vigilant. That was detected last week in Michigan. The person has since recovered. So where do things stand at this point in the outbreak? NPR's Will Stone joins us now to bring us up to date. Will, this human case - anything new there?

WILL STONE, BYLINE: It's a similar situation as in that first human case, which was found in early April in Texas. Like that one, the infection turned up in a dairy worker, this time in Michigan. That makes sense, because these workers do have the highest risk of exposure given their close contact with dairy cattle. The person's only symptom was conjunctivitis, also known as pink eye. Interestingly, they had to swab the person's eye to get a positive sample. It did not come up positive when they did their nose.

MARTÍNEZ: OK, so how concerned should we all be?

STONE: This wasn't all that big a surprise. As scientists I've spoken with have said, they suspected there are other human cases flying under the radar because these tend to be mild. Still, I would say it's a wake-up call. The outbreak in cattle has not just fizzled out yet. The CDC stressed that it found this human case because they've ramped up their surveillance. Dr. Diego Diel is a virologist at Cornell. He says it's quite possible this worker got infected from being splashed or somehow exposed to infected milk. But the truth is, A, there are still many unknowns, including exactly how this is spreading between cows. The theory has been it's mostly occurring during the milking process, and new research also shows that raw milk can infect mice in the lab. Here's Diel on the situation.

DIEGO DIEL: I think we are in the middle of a black box, to be honest with you. I don't think we know the real dimension of the infection, how widespread it is. I suspect that we are not testing enough to really assess what the real scenario is.

STONE: Federal agencies have poured a bunch of money into trying to get more buy-in from dairy farms, so there can be more testing and studies on the ground. So far, though, it seems like that is still pretty challenging. Not that many humans have been tested, and officials with the CDC have said they'd like to be doing more, but cooperation has been, quote, "variable."

MARTÍNEZ: All right. So what are scientists focusing on, then?

STONE: They're paying attention to whether any known or troubling mutations have popped up. Scientists have a sense of what some of the alarming ones would be, for example, changes that would indicate the virus is getting better at binding to receptors in our upper airways. We have not seen that yet. Troy Sutton at Penn State University is studying how bird flu is spreading among mammals. He recently published findings showing there was a low level of airborne transmission between ferrets in the lab. But this was an older form of the virus, the one that was spreading in Europe at a mink farm, and that was before the virus came to North America and underwent some changes. So while that was not the same virus, Sutton says it is still notable because they had not really seen this before with this particular version.

TROY SUTTON: These viruses seem to be getting better at infecting mammals. Does that mean they're getting better at infecting humans? We can't make that statement. But, you know, definitely the more a virus seems to be able to infect mammals and cross the species barrier, the more concerned we should be.

STONE: Sutton says the fact is, scientists don't fully understand all the implications of the changes in this virus. But to be clear, the CDC says right now the risk to the general public is still low.

MARTÍNEZ: All right. Good to know. That's NPR's Will Stone. Will, thanks.

STONE: Thank you. Transcript provided by NPR, Copyright NPR.

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Will Stone
[Copyright 2024 NPR]
A Martínez is one of the hosts of Morning Edition and Up First. He came to NPR in 2021 and is based out of NPR West.