A novel subtype of influenza A virus: H18N11

Influenza A viruses are designated according to their hemagglutinin (H) and neuraminidase (N). Until recently, 16 different types of hemagglutinin (H) and 10 different types of neuraminidase (N) were known. That means that a total of 160 different subtypes of the Influenza A virus were possible to exist.

Then in March 2012 news appeared[1]  that a novel influenza A virus (H17N10) was circulating in fruit bats from Guatemala (Central America). Now, in October 2013, another new influenza A virus was identified[2]  from Peruvian bats. The genes that encode the surface proteins of the new virus from the flat-faced fruit bat were designated as new subtype H18N11. Officialy it is now named A/bat/Peru/10.

[Image: Mónica Díaz: Peruvian Fruit Bat]

The crystal structures of the hemagglutinin and neuraminidase proteins indicate that sialic acid is not a receptor for virus attachment nor a substrate for release, suggesting a novel mechanism of influenza A virus attachment and activation of membrane fusion for entry into host cells.

This all means that we now know of 18 different types of hemagglutinin (H) and 11 different types of neuraminidase (N) and it indicates that a total of 198 different subtypes of the Influenza A virus might exist.

In summary, the findings indicate that bats constitute a potentially important reservoir for influenza viruses. That makes predicting the next epidemic even more problematic.

[1] Tong: A distinct lineage of influenza A virus from bats in Proceedings of the National Academy of Sciences of the United States of America - 2012 
[2] Tong: New World Bats Harbor Diverse Influenza A Viruses in PLos Pathogens - 2013