MICHEL MARTIN, HOST:
More people are catching bird flu. Five cases were recently detected in workers at a poultry farm in Colorado. Meanwhile, dairy herds are still testing positive. Federal health officials maintain that it's still possible to get a handle on the outbreak, but not everybody is so optimistic. NPR's Will Stone is with us now with the latest. Good morning, Will.
WILL STONE, BYLINE: Good morning.
MARTIN: Do we know how these folks in Colorado caught the virus?
STONE: We have a pretty good idea. They were working at a big commercial poultry farm that had an outbreak of H5N1 bird flu, and these workers were responsible for cooling and disposing of these birds, which means they were handling them. They were putting them in carts that are used to euthanize the animals. That's already a high-risk activity, but it turns out, these barns were also baking in the summer heat. There were big industrial fans going. All of this made it hard for them to properly wear protective equipment over their eyes, their mouth and their nose, and Jennifer Nuzzo, an epidemiologist at Brown University, says it's really not surprising that some of them were infected.
JENNIFER NUZZO: It's gambling with people's lives. We're fortunate that these workers didn't get severely ill, but from everything we know about this virus, we have every reason to worry that someone could become severely ill.
STONE: And, Michel, that's because bird flu can be quite lethal, although so far, it has only led to mild illness in the handful of cases documented in the U.S. since April.
MARTIN: Will, how concerning is it that new human cases are being found, even after months of trying to get this under control?
STONE: It's definitely bad news. Nuzzo and other scientists I speak to say it just shows there need to be more biosecurity measures in place to protect workers. The poultry industry does have a lot of experience in this area, because they're used to bird flu. At the moment, it still seems like dairy cattle are fueling this outbreak on farms. In fact, based on genetic sequencing of these Colorado cases, the current hypothesis is that there was a spillover from dairy cattle to poultry, and that is actually what led to these human infections. Now, luckily, it doesn't look like the virus that infected these workers has undergone changes that would allow it to spread easily between humans, but of course, this is what scientists like Troy Sutton at Penn State are watching super closely.
TROY SUTTON: Every time you give avian virus a chance to infect a human, it's like buying a lottery ticket for a lottery you don't want to win. It is alarming to me that we continue to see more people getting infected, not unexpected.
STONE: Sutton says not only do you want to keep people from getting sick, obviously - you really don't want to give this virus time to adapt to humans.
MARTIN: All right, so here's the scary question. Do we have any indication that that's already happening?
STONE: So at the moment, scientists say this is still fundamentally a virus that likes birds. It doesn't easily infect the upper respiratory tract of humans, but Thomas Peacock at The Pirbright Institute in the U.K. says this version of the virus circulating in dairy cattle does have some new mutations which are helping it out.
THOMAS PEACOCK: It doesn't have the ones we're most worried about, so the ones that make the virus better at spreading by the airborne route from human to human, but it 100% has several mutations that enhance its ability to replicate in mammalian cells.
STONE: Peacock says there are still lots of questions about exactly what these changes are doing. He says what's clear, though, is that the U.S. has not yet managed to contain the situation.
MARTIN: Well, Will, thanks for this reporting, and obviously, keep us updated.
STONE: I will. Thank you.
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