Three major developments in a single day have a biologist on the frontline of avian influenza research worried it poses an increasing threat to animals and humans.
Dr Jenna Guthmiller has been studying the virus for years at the Department of Immunology and Microbiology at The University of Colorado Anschutz Medical Campus, and she’s concerned deadly strains of this virus are being allowed to spread “uncontrolled”.
“We are just seeing the tip of the iceberg. The number of people who are at risk of being exposed to this is really very high,” she said.
What you need to know about avian influenza
What are the three bird flu developments?
The first worrying development was confirmation that a human had died from the H5N2 subtype in Mexico – and according to the World Health Organisation this was the first-known fatality from this strain.
H5N2 and H5N1 are part of the same family of influenza A viruses, but while H5N1 has been known to infect humans for decades this is the first reported case of H5N2 in humans.
The second “big thing” announced on Wednesday was the detection of H5N1 in field mice in the US state of New Mexico, at a location close to known infected cattle herds.
“This is unheard of that mice in nature are infected with influenza viruses, they’re actually thought to be incredibly refractive of flu. So that was striking,” Guthmiller said.
“And then the third issue is, we have a new state in the US [Iowa] that has a herd infected with H5N1.”
Virus expert worried about spread of bird flu to humans
Although Guthmiller believes there’s been a “huge barrier” stopping H5N1 evolving into a pandemic in humans, she thinks the virus appears to be “ramping up” since it spread to dairy cows.
“It’s clear that this cow H5N1 has jumped back into birds and where the concern with that lies is that birds don’t follow the rules of fences,” she said.
“This could result in the virus jumping back into other mammals and continuing to spread. As we see more mammals become infected I think the concern that this could adapt, and we become one of those incidental mammal hosts, increases.”
Guthmiller confirmed she’s “genuinely concerned” about the virus’s potential to further impact humans.
“I feel the outbreak is uncontrolled, and we just do not have a good grasp of the breadth of the outbreak – how many farms are affected, how many different areas, the number of cows, the number of other animals that are getting infected,” she said.
To date, all infections in humans are believed to be linked to contact with animals carrying the disease. But if someone was to present without any links to a farm or pet animals, Guthmiller believes it would be “genuinely worrying”.
“If they really had no exposure to animals, that would be really the most concerning factor, because it would imply human-to-human transmission,” she warned.
Could a bird flu pandemic sweep across the world?
Unlike Covid-19, there have been no confirmed human-to-human cases of the current highly virulent H5N1 strain that’s killed tens of millions of poultry and wild birds around the world. The strain has spread to every continent, including Antarctica, except for Australia.
Guthmiller predicts if the virus was to become a problem for humans it would be a “slower burn”.
“I don’t think it’s going to be a singular event where a dairy farm worker gets exposed to milk, gets infected, and that’s going to be the thing that sets off a pandemic,” she said.
“The virus is going to jump from cows to another animal, then jump back into dairy cows again. It’s really just trying to figure out how it can keep going and infect the most amount of things. And I think at some point, it has a very high likelihood of gaining that capacity to make humans one of those hosts. If we really do not get this under control, I see those odds increasing further.”
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