Frequently Asked Questions

I read that the flu going around is H3N2, but that the big concern now is Bird Flu H5N1. What do those letters mean?

Hemagglutinin (H) is a type of protein found on the virus that allows it to attach to the cell it infects. There are 16 known different H types. The first three H1, H2 and H3 are normally found in human influenza viruses.

Neuraminidase (N) is a type of protein also found on the surface of the virus. This protein aids in the efficiency of releasing the virus' progeny from the infected cell, thus promoting the infection. There are nine known different N types. Subtypes N1 and N2 are known to cause human epidemics but subtypes N 3 and N7 have also been identified in some who have died of influenza.

The Avian or Bird Flu H5N1 normally does not infect humans. But the current human infections have caused worry as the virus has changed or shifted so that man can be infected. So far, the virus is hard to contract in humans unless they have close contact with infected poultry, droppings, or dead birds. Human mortality rate is currently at 56% of those infected. Additional changes may allow it to more easily infect humans. Public health authorities around the world are on alert for these changes.

As emergency responders we do not have to track H and N numbers, but rely on public health authorities to tell us which infect humans.

Source: U.S. Centers for Disease Control and Prevention, World Health Organization, Wikipedia