Submitted by PURELY_TO_VOTE t3_10x2tls in askscience
extrapolatethiscurve t1_j7sklck wrote
-Influenza viruses bind to certain sialic acid-containing receptors on the surface of cells, using them to get inside and take over. These receptors come in multiple varieties; human influenza viruses bind to alpha-2,6 receptors, while the viruses that infect birds prefer alpha-2,3.
This difference is important. Humans also have alpha-2,3 receptors, but they tend to be deep in the lung rather than in our upper airways. That makes it very hard for H5N1 to get a purchase, giving us good protection from the virus. The tradeoff is when it does take hold, that infection is deep in our body, often leading to severe disease. This explains why bird flu infections in humans are extremely rare but often lethal: the World Health Organisation has tracked 868 cases and 457 deaths since 2003.
...Indeed, the virus isolated from the mink in Spain had an uncommon mutation that allows it to more-easily infect mammal cells.
And it does not need to take many more steps before it is a danger to humans. Lab evidence suggests as few as five specific amino acid changes are all H5N1 needs to spread effectively in humans. Wild viruses with two of these mutations have been spotted. “It’s not really a big stretch for it to happen,” says Horwood.
Is this an imminent pandemic threat? “No,” says Professor Ricardo Soares Magalhães, director of the Queensland Alliance for One Health Sciences at the University of Queensland, “the situation is indeed concerning, but not a matter for alarm.”
The Spanish researchers tested all the people who worked with the mink but did not turn up any evidence of H5N1, suggesting the virus has not picked up a mutation that enables easy spread to humans.
And CSIRO bird flu expert Dr Frank Wong points out there’s no evidence the virus has a new mutation that allows it to spread easily in mammals. The mink, which are jammed together in small cages, may be a special case. “The risk of onward, mammal-to-mammal transmission has not really changed,” he says. “It’s still a bird-adapted virus.”
Nor is the situation analogous to COVID-19. That virus was (unfortunately) unexpected by health authorities; scientists have tracked H5N1 for years and have prepared vaccines and antivirals.-
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