Influenza A(H3N8) Virus in Humans

We know that the Influenza A Virus likes to mutate via antigenetic drift (small, incremental mutations) and antigenetic shift (abrupt, major change) to evade our immune system. It also helps them to jump from one species to another.

An example is Influenza A(H3N8) Virus that is known to infect wild birds, although it has also been detected in live poultry markets in Asia. Occasionally, Influenza A(H3N8) viruses have been associated with disease in dogs, horses, pigs, donkeys, and most recently seals.

But on 25 April 2022, the Chinese health authorities reported an influenza A(H3N8) infection in a 4-year-old boy from Henan Province. He developed fever on 5 April 2022, cough and shortness of breath in the following days and was admitted to the hospital in critical condition on 10 April 2022 with severe pneumonia.

No human infection with influenza A(H3N8) Virus had been recorded before this case. Genetic analysis of the virus confirmed it is of avian origin. As said above, avian Influenza A(H3N8) viruses are commonly found - but not associated with disease - in wild birds and live poultry markets in Asia.

However, the genetic composition of A(H3N8) viruses detected in animals to date is different from that detected in the patient.

While further human infections with Influenza A(H3N8) viruses cannot be excluded, the Chinese authorities claim that the risk is low. The likelihood of sustained human-to-human transmission is also regarded as low.

That the Chinese authorities downplay the severity of this novel variant is nothing new. I think that a novel variant of Influenza A(H3N8) Virus that is able to infect humans should be regarded with some anxiety.

At the moment, we know know next to nothing about its ability to spread and to infect people. But we do know that a little boy was admitted to hospital with severe pneumonia.