13. We are all familiar with the flu virus, this is the same virus that causes typically mild illness during the winter months, with the most common versions we normally encounter being the H1N1 and H3N2 subtypes. Subtypes for the flu are somewhat similar to the different variants of SARS-CoV-2; when a new variant or subtype starts spreading, chances are that previous vaccination or infection will no longer be as protective. The same is true for flu, previous infection or vaccination with an H3N2 subtype will likely not offer much protection against infection with an H5N1 subtype.
However, the H5N1 flu virus is quite different from the types of flu we normally think of. First, these viruses usually spread between birds, where it is often lethal, giving them the name Highly Pathogenic Avian Influenza Viruses (HPAI), which includes H5N1 and other similar flu subtypes. Outbreaks of these viruses can have devastating effects on both wild and farmed bird flocks. Thankfully though, the H5N1 virus doesn’t spread to people very easily and even then, further person-to-person transmission is quite rare.
In 2022, the virus jumped from birds to farmed minks in Spain. There the virus caused severe illness in the minks, but also began to spread from animal to animal, something that hadn’t been seen before and may have been facilitated by the close confines the farmed animals are kept in.
The flu virus evolves quickly and so there were fears that rapid evolution of the virus in minks would result in a virus that could easily infect people. Thankfully, this didn’t happen, but we are seeing more and more cases of mammals infected with H5N1, from seals to bears, with some of these infections showing evidence of mutations that enable better growth and transmission in mammals.
The good news is that this evolution to a human-transmissible version of H5N1 is not a sure thing. We’ve been tracking these viruses since 1996 and despite many chances, the virus has never made this jump. Even with the significant increase in avian H5N1 outbreaks in recent years, the number of human cases has remained very low. It’s very possible it will never happen, that the virus is too well adapted to birds and that limits its ability to infect people.
(Taken from BBC Science Focus Magazine)
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