Influenza A Virus in Bats [3]

Bats are perfect hosts for devergent strains of the Influenza A Virus.

[Image credit: BatWorld - Egyptian Fruit Bat]

Here and here, I had already reported about strange Influenza viruses, A(H17N10) and A(H18N11), in South-American bats, the little yellow-shouldered bat (Sturnira lilium) in Guatemala and the flat-faced fruit-eating bat (Artibeus jamaicensis) in Peru, respectively. With a sense of relief, the researchers were unable to propagate this virus in cell cultures, suggesting it was a long way from being able to pose a threat to humans.

In 2015 serological evidence was published of Influenza A Viruses in Frugivorous Bats from Africa - which suggested prior H9 influenza infection in bats tested in Ghana - raising new questions about the range of flu viruses carried by bats[1]. The researchers were a bit worried about this and concluded 'As H9Nx is associated with human infections, the implications of the findings from a public health context remain to be investigated'.

In 2018 nature surprised us again when a study was published that described the isolation and characterization of a genetically distinct Influenza A H9-like virus from Egyptian fruit bats (Rousettus aegyptiacu), captured in an abandoned mudbrick house in a village in the Nile Delta region in March 2017. The virus already had the ability to replicate in the lungs of experimentally infected mice[2].

Then, in 2023, preliminary news arrived that bat Influenza A (H9N2) Virus identified in Egypt exhibited high replication and transmission potential in ferrets, efficient infection of human lung explant cultures, and marked escape from the antiviral activity of MxA (Myxovirus Resistance Protein A, a marker). Together with low antigenic similarity to N2 of seasonal human strains, bat Influenza A (H9N2) Virus meets key criteria for pre-pandemic Influenza A viruses[3].

[1] Freidl et al: Serological Evidence of Influenza A Viruses in Frugivorous Bats from Africa in PloS One – 2015. See here.
[2] Kandeil et al: Isolation and Characterization of a Distinct Influenza A Virus from Egyptian Bats in Journal of Virology – 2019. See here.
[3] Halwe et al: The bat-borne influenza A virus H9N2 exhibits a set of unexpected pre-pandemic features in Brief Communications – 2023. See here.