Bird Flu Update: H5N1 Virus Still Widely Circulating

It’s almost Thanksgiving, and that can mean only one thing — it’s the perfect time to talk about avian influenza!

I’m not actually trying to ruin your holiday. But at the recent annual meeting of the Association for Molecular Pathology, a gathering of thousands of people who run clinical testing laboratories, a scientist from Johns Hopkins University offered an update on the threatening H5N1 strain of this virus. With the current state of the Centers for Disease Control and Prevention, insight into the ongoing H5N1 outbreak that started in the U.S. in 2022 has been hard to come by. This talk was a welcome change of pace so naturally I wanted to share with my readers.

Andrew Pekosz, an infectious disease specialist, spoke about this strain of H5N1, which has been circulating around the world in recent years and has led to the culling of nearly 200 million birds just here in the U.S. The reason this strain is so scary is that it seems to have no trouble spilling over into different species — and not just birds, but many types of mammals including humans. That’s indicative of a highly adaptable virus, one that could potentially make the leap to respiratory transmission.

So far, though, that has not been the case. Despite the huge number of infected cows and the 70-plus humans infected in the U.S. to date, there is no evidence of widespread transmission from one animal or person to another (although Pekosz did cite recent observations of sea lions infecting each other in South America). Cows appear to be primarily getting infected by the milking equipment used on dairy farms rather than through respiratory transmission between cows, and most humans who have been infected came into contact with infected birds, cows, or other animals.

While the lack of person-to-person transmission is good news, Pekosz warned against letting our guard down. The sheer number of spillover events, or transmissions from one species to another, gives the virus frequent opportunities to evolve. It only takes one spillover event with the right set of mutations to spark a new pandemic.

To prepare for the worst, Pekosz and his team conducted an analysis to understand whether humans have any natural immunity that could help protect us if H5N1 were to morph into a respiratory pathogen. As expected, since humans typically are not susceptible to infections by H5 flu strains, there was very little immunity; the one hopeful note came from existing protection against the N1 part of the virus. Should H5N1 start spreading among people, Pekosz said, it might be helpful to use vaccines that boost N1 protection to help our immune systems fight the virus.

And on that note, I wish you all a very happy Thanksgiving!