Combined infection with bird flu and human flu could lead to mutations of new viruses that could have dangerous public health consequences, agencies have warned.
This is following the news that mutations of bird flu have occurred within a Louisiana patient and a teenager from Canada who both suffered with severe symptoms, potentially raising the risk of serious human infection among others.
The U.S. Centers for Disease Control and Prevention (CDC) advises on their website that Americans, particularly those at high risk of bird flu such as farmworkers, should get the flu vaccine this season, even though it only prevents seasonal flu.
“This is because it can reduce the prevalence and severity of seasonal flu and might reduce the very rare risk of coinfection with a human seasonal virus and avian virus at the same time, and the theoretical risk that reassortment between the two could result in a new virus,” the CDC says.
“Such dual infections, while very rare, could theoretically result in genetic reassortment of the two different influenza A viruses and lead to a new influenza A virus that has a different combination of genes, and which could pose a significant public health concern.”
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Bird flu and some versions of human flu are very similar; bird flu is more formally known as avian influenza A(H5N1) and dominant strains of human flu include influenza A(H1N1) and influenza A(H3N2).
This means that all three of these variants of flu are different versions of influenza A, all of which use protein components called hemagglutinin (H) and neuraminidase (N).
Pediatric infectious diseases specialist at the University of Iowa and member of Iowa’s Johnson County Board of Health Dr. Melanie Wellington recently appeared in a YouTube video by Johnson County Public Health explaining the risk of bird flu combined with human flu.
“When a flu virus infects a cell, its genetic material goes in as multiple different segments or pieces,” she explained in the video, posted November 18, 2024. “When it wants to make a new virus, it loads the new virus up with one copy of each piece.
“If by chance a bird flu virus and a human flu virus infected the same cell, it would load one copy of each piece, but it wouldn’t be able to tell if those pieces had come from the bird virus or the human virus.”
When new copies of the virus would be made, said Wellington, pieces of segments might be used from both bird flu and human flu.
“Just like that, a new virus could be cobbled together from the other two viruses, and it would be something new that nobody would know how to respond to,” she said.
This possible mutation is worrying public health officials and scientists. A new virus made from bird flu and human flu could be transmissible among humans but something we did not have immunity against, which could lead to a pandemic situation.
Professor Edward Hutchinson, a virologist at the University of Glasgow, previously told Newsweek: “The more encounters the virus has with humans, the more chances it has to adapt to growing in them, and if it can mix and match its genes with a human seasonal flu, that could accelerate this process.
“When an influenza virus from a different animal adapts to spread effectively among humans, the result is pandemic.”
Currently, there have been 66 confirmed human cases of bird flu in the U.S. and seven probable infections.
These are all believed to be “spillover” infections, meaning they were caused by exposure to other animals such as birds or cows, and no bird flu infections are believed to have been passed from one person to another, so the CDC maintains that risk to public health is low.
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