The 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.
One thing the CDC has actually improved on since COVID a little bit is communication, rapid communication. For example, they put out a technical report, some updates, a preprint, et cetera. What I don’t think is getting better is the testing, because of the fragmented and decentralized public-health system, which is incredibly challenging to activate and to get a national picture with even if we were doing testing — and we’re not doing testing. We don’t know, still, how big this outbreak truly is.
On the communications front — I understand why public-health agencies wouldn’t want to freak people out unnecessarily. But this is a similar dilemma to the one they faced with COVID, which is how much to tell people. Instead of giving the public all the information they had and trusting them to make decisions, they parceled it out. There seemed to be a human-psychology element to the communication strategy, which was not a good idea.
It drives me insane. You have to give trust to gain trust, right? And honest, frequent, direct communication earns public trust and confidence. It’s that simple. But if communities are starved for good information during these sort of outbreaks or emergencies, it leads to unnecessary anxiety, confusion, and incredible frustration. And it just looks like they’re not credible or know what they’re doing.
So even if CDC has been better than with COVID, which was a very low bar, that doesn’t mean the other government agencies have been doing a good job at all. And on top of that, it hasn’t been a one-voice, coordinated front.
Which other agencies are in the mix primarily?
USDA, FDA, Health and Human Services, and CDC are the big players.
A big obstacle here is that the testing is voluntary on farms. There are misaligned incentives at play — why would you want to expose the fact that there’s bird flu all over your farm, right?
Exactly.
Is there no way around that dilemma, no way of mandating more testing? That seems crazy.
It is. It’s crazy to me too. But there’s a really fine line here. When you start making people do stuff, you start having to cash in your brownie points, and it hurts trust. The big question I haven’t been able to find an answer to is this: What is that “oh shit” line where we need to actually crack down and be like, “Guys, we have to be starting to test this on a systematic level among humans.”
I will say we have gotten some creative workarounds — for example, testing milk supply in grocery stores and testing wastewater to try to understand how much bigger this outbreak is. The CDC said it’s investigating Florida and Illinois, which have high wastewater levels but do not have herds detected with flu. So it’s really putting a puzzle together, which seems to be incredibly challenging. And that’s really hard to watch on the heels of COVID.
I never was quite clear on how accurate the wastewater stuff was. Was it considered to be a reliable indicator for COVID in the end?
Wastewater ended up being one of the most effective tools we had around infection in the United States. And I do think that’s one thing that survived from the pandemic de-escalation. But activating that for an entirely different disease comes with its own questions. Is this human or animal wastewater? If it is animal wastewater, how is it getting into our wastewater system? Is it milk-dumping? Is it infected feces? There are so many questions. And it’s imperfect, especially since we’re just testing flu A, not H5. Which will be highly problematic come fall if this is continuing to spread.
Why fall?
Because that’s when the flu starts ramping up again. And so we won’t be able to differentiate whether these signals are just your normal flu that we see every year, or H5. We really need to figure out how to differentiate that before the fall. And we have time — we just need to move.
To go back to the actual virus itself, is there something particular you’re looking for as a next signal that this is getting more serious? You mentioned pigs.
Johns Hopkins did this really great risk assessment of the different levels of risk and when our concerns should really go up. Basically, the next level is whether we start seeing it in pigs. After that, it’s small human clusters, and then the alarm-five scenario is when we see sustained human-to-human transmission. We’re definitely in the beginning, but if this is any indication on how we’re going to do when there’s an alarm five, I think that’s very concerning.
Have you seen any other world governments do a better job on this particular thing? Is it like COVID in that way?
The rest of the world is very nervous because they’re watching how the U.S. responds.
They’re nervous about everything in the U.S. right now.
Cow-to-cow transmission is only in the United States. Canada has been testing their cows because a lot of our cows go there.. They haven’t detected anything, but it’s really unfolding in the United States. And that’s where a lot of the frustration comes from, because this is a global threat, and so other countries need data, and when and how to start testing and getting that sort of transparency. And so that adds a whole other level of pressure to this response.
We’ve had so many influenza epidemics in the past. Is it just inevitable that we’ll have another one in the future?
I wouldn’t say 100 percent. But if you ask ten epidemiologists, nine of them would say the next pandemic is flu. It was surprising to a lot of us that the last pandemic was COVID, honestly. We always expect it to be flu, just because of how much this jumps.
COVID was something people hadn’t nearly as much experience with. We know what flu is. Would making a vaccine for that actually be easier in that regard since we sort of have an idea of what we’re dealing with?
You make a really good parallel here — COVID was completely novel. The good news is we’ve been following H5 for the past 25 years, down to the point where we know exactly where on the virus it needs to mutate to become more human-to-human transmissible. In fact, we have a stockpile of vaccines against H5N1. Now, how fast we can create, manufacture, and distribute vaccines is a whole different question.
The bad news is we think the H5N1 is far more fatal than COVID-19. COVID, with just a 1 to 2 percent fatality rate, already overwhelmed our hospital systems. And so we really don’t want this.
This may be a stupid question, but could they make vaccines for animals for this bird flu?
They can, and that’s not a stupid question. And it’s actually being discussed very heavily right now. There’s some challenges with it, though. The biggest challenge is that if you start inoculating animals — and some countries do this with birds — it’s actually harder to understand how this virus is spreading. Because it’s harder to differentiate the asymptomatic animals there. The other problem, from my understanding is on the agriculture side, is that a lot of countries won’t accept animals that are vaccinated.
So there’s some pretty tough decisions they need to make. Another concurrent question is when do we start vaccinating farm workers? Especially since they can’t be wearing PPE, and some farmers said that it’s way too hot to be wearing masks.
Last year you said, “I do not think we’re at a phase where the public needs to be worried because there’s no action connected to that worry … right now the action is just to be aware.” Is that still pretty much where you are on this?
Yeah, 100 percent. I put out a newsletter last week because I keep getting this question from family and friends. “How concerned should I be?” And I am telling people that this should only take up 2 to 7 percent of headspace right now. It’s something to watch. But like I said a year ago, there’s nothing to do, really, other than don’t touch dead birds, don’t drink unpasteurized milk, and maybe call your congressman to encourage biosecurity support. Other than that, we really needed targeted communication to those that are at higher risk, and that’s farm workers right now.
And this is another mistake we made during the pandemic. Risk is not uniform, and people really need to understand what risk category they’re in so they can be appropriately concerned and also take action if they need to.
I find the lack of good communication confounding.
It’s deflating, honestly. It’s deflating and depressing.
This interview has been edited for length and clarity.
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