he H5N1 influenza has killed tens of millions of birds over the last few years, and it’s not slowing down. Instead, it has confounded expectations by spreading into animals once thought immune, and even to at least one person in the United States. (There is no evidence of human-to-human transmission, and risk to the public is still considered low.) As with any viral outbreak, the pathogens themselves aren’t the only challenge. The sluggish, imprecise response to H5N1 from federal and state authorities carries unavoidable echoes of COVID. I spoke with epidemiologist and data scientist Katelyn Jetelina, who writes a popular public-health newsletter, to make sense of where bird flu might be going and how some agencies are repeating past mistakes.
When we last spoke about this in March 2023, the big concern was that bird flu had been spreading among minks. Things have really progressed since then, especially in recent weeks. Now it’s spreading throughout the cow population, which until recently was unheard of. The question of human transmission aside, do you think it’s inevitable that bird flu will keep moving into other animals?
I think there are two questions. The first is will it die off among cows, or will it continue to have sustained transmission? We don’t know the answer yet. And it’s going to be really hard to get that answer because of the lack of testing and surveillance we’re doing at the moment. And the second question is how many more hosts is this going to find to become endemic in another animal population? This is the first time we’ve really seen cow-to-cow transmission, but the biggest concern we have is the physical proximity they have to humans and other farm animals, possibly pigs, which are non-mixing vessels. So that’s how I’m thinking of it right now.
I was reading an interview Stat News’ Helen Branswell did with the head of the CDC’s influenza division. The agency faces a lot of legitimate hurdles, like the fact that states have to invite them in to do testing. But its overall approach seems scattershot, and after COVID, my confidence in public-health authorities to get out in front of this stuff is low. How do you feel about the response so far?
The first challenge is that the players involved here are unique and not necessarily known to play well in the sandbox together. They have their own priorities, legal authority, and level of agility and experience, and they really need a coordinated response from our government.