After egg prices soar and infections spread in chickens, cows, and cats, a BU virologist is advocating for more testing and tracking
Nearly a year after the first person was infected with the H5N1 strain of avian influenza, commonly called bird flu, from a sick dairy cow, the virus is still hurting farms and the agriculture industry—and the wallets of everyday Americans. The loss of millions of chickens because of the disease has sent egg prices soaring—peaking in February with 15 percent higher-than-average prices. Health officials recommend a number of food safety precautions for consumers, like avoiding raw milk and undercooked eggs, since the virus can be present in unpasteurized products.
“We are a country where there is now egg rationing because of a virus. That seems like something we should be paying very close attention to,” says John Connor, a Boston University Chobanian & Avedisian School of Medicine professor of virology, immunology, and microbiology who studies virus-host interactions. “Plus, this is a virus that poses a threat to human health.”
There have been at least 70 confirmed human bird flu cases in the US, with over half of them from interacting with infected cows. In January, a person in Louisiana was the first known to die from the bird flu in the US. H5N1 outbreaks have popped up around the world since it was first identified in China in 1996, causing upwards of 1,000 documented human cases in multiple countries, with about a 50 percent mortality rate.
“Influenza viruses are diverse enough that they wear a bunch of different masks to infect different animals, including us,” says Connor, who’s also affiliated with BU’s National Emerging Infectious Diseases Laboratories (NEIDL). “The thing that we’re really worried about is a flu transmitting from person to person, where we don’t have a good vaccine or existing immune response.”
Thankfully, there has not been documented person-to-person H5N1 transmission. But data released in February suggests that infections have gone undetected between cows and humans, including in three veterinarians who worked with cattle and poultry, raising questions about gaps in current transmission data. This is particularly concerning, because the better the virus gets at infecting and spreading between different animals, the more possibility it has to mutate in a way that can adapt to humans. H5N1 has already jumped from birds to a number of mammals besides cows; rats, mice, mink, bears, seals, and foxes are on a list of species that have had confirmed infections. Notably, a growing number of house cats have died from H5N1 and appear to be particularly vulnerable to severe disease.
The Brink asked Connor about the current state of the virus, how concerned we should be, and what solutions he hopes are on the horizon.
Q&A
with John Connor
The Brink: Is this virus acting in a way that was expected by scientists? Or are you surprised by how it has continued to spread rapidly?
Connor: When we first noted that the virus was replicating in cows in 2024, to me that was a huge, and surprising, event. A virus that had largely been locked in birds started showing up in cow milk, and it has since infected cats and rats on farms. Now, a year later, it’s clear that this virus is not just spilling from birds into cows, but has also become quite comfortable replicating and spreading between cows. It’s making billions of copies of itself in the milk of these cows. This opened up a new front where influenza can attack us.
The Brink: Can you explain why H5N1 is different compared to other strains of flu?
When we get our seasonal flu vaccine, we get protected against H1N1, H3N2, influenza B. We aren’t being protected against H5N1, and that makes everybody super nervous. The reason people have been concerned about H5N1 is, in past instances when it jumped from birds to humans, people who were infected and hospitalized had very severe illness. It has shown to be much more deadly than seasonal flu strains. So, from a public health standpoint, that’s the worry. What has not been clear, however, is if there is something particularly dangerous about the virus coming from cows directly into people. Is there something about these new virus mutations in cows that makes it not as severe for humans? We don’t know, but from the current cases of H5N1 in the United States, many of the cases have been relatively mild.
The way I think about influenza viruses is that they are always trying to figure out how to open doors to get in. Influenza spreads in multiple different animals, including us. Flu viruses, including the seasonal flu we get vaccinated for, very frequently originate in animals. We know that the major way flu reaches humans is from birds or pigs.
The way I think about influenza viruses is that they are always trying to figure out how to open doors to get in. Influenza spreads in multiple different animals, including us. Flu viruses, including the seasonal flu we get vaccinated for, very frequently originate in animals.
John Connor
The Brink: The virus is still considered a low threat for humans and, at the same time, it feels like it’s inching closer and closer to us. Can you explain the threat level and how it remains low?
The threat level of people being infected with H5N1 is much higher now in the United States than it has been at any time previously. However, overall, it’s still very low. Compared to how many seasonal flu cases were reported this winter—which was an intense flu season—bird flu remains a very minor contributor. At the same time, this is something we should not be ignoring. Now, H5N1 is able to reach us from more places: birds, cows, cats, and rats. As that number of places increases, the number of situations where we can touch that virus increases, and I think these viruses are always trying to find a way to open doors and spread.
The Brink: Is the current level of surveillance enough to get a full picture of the state of H5N1?
I think there should be more. There are efforts ongoing, and I applaud them. It would be ideal for [more leaders] to take a greater interest and do more surveillance to understand where the virus is and isn’t circulating. We got surprised when it started circulating in cows, even when there was evidence that was a possibility. I don’t think we’re looking close enough to know if it’s circulating in other animal species, and it would be really nice to have more information so we don’t end up surprised again. For example, how many cats out of thousands of household cats in the US have encountered the virus? That would give data that can inform people’s decision-making and risk assessment for whether they want to limit their pet’s outdoor activities.
The Brink: For people who have indoor-outdoor animals, for example, what do you think is the appropriate level of precaution to take at this point?
I have a hard time knowing exactly how to assess that. In a sense, the news spotlight shines on the human H5N1 cases when they happen. But there has been evidence of a handful of people, specifically veterinarians, testing positive for the antibodies of the virus—meaning they encountered it and didn’t know they even had it. So, it’s impossible to know what else is outside of the spotlight, and what we’re missing. What I hope for is more spotlights so we can better answer these questions.
The Brink: Are you concerned at all about our country’s ability to track and detect this virus?
I am concerned. I’m advocating to have more tracking and testing, and I believe that this is a crucial time to watch this virus closely. I see this as national defense. It’s understanding threats from outside and hopefully being able to respond to them. Right now, when you go to the store and see [high] egg prices, that is because of a virus. My advice to any public health official would be to put resources toward making certain we watch it, and don’t get smacked in the head with it later.
The Brink: Are there any promising solutions on the horizon?
One thing that we don’t have yet is a good, inexpensive poultry vaccination. Importantly, this would lower the virus amplifying through large flocks of poultry. Because the more the virus amplifies, the more opportunities it has to spread and mutate. I’m not interested in giving a poultry farmer an extra expense, but being able to block bird infection as an avenue for the virus to amplify would be great. We ideally need a vaccine available for cows, too. Any solution will defy simple answers.
This interview was edited for length and clarity.
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