Avian flu isn’t ‘one mutation away’ from becoming the next pandemic – yet

In early December 2024, a group of researchers published an article in the journal Science, entitled “A single mutation in bovine influenza H5N1 hemagglutinin switches specificity to human receptors”. Some media outlets somewhat exaggeratedly took this to mean that we are one mutation away from bird flu “becoming the next Covid”.

There are currently no documented cases of human to human transmission of bird flu, also known as avian flu H5N1, though there is concern that the virus, which has spread among farm cows in the US, may mutate and spread to humans, leading to a flu pandemic.

Molecular barriers

One of the barriers currently preventing avian viruses from spreading to humans has to do with the way different flu viruses bind to their host. This happens when a flu virus’ haemagglutinin (HA) binds to a receptor. In the case of flu, the receptor contains sialic acid molecules.

However, there are various types of virus receptors. The HA of avian influenza viruses binds to “avian-type” receptors containing α2-3 sialic acid. However, HA from human influenza viruses binds to different receptors – those with α2-6 sialic acid – which are abundant in our upper respiratory tract cells.

For the avian flu virus to be transmitted from one human to another, it would first have to develop the…

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