What is flu?
The influenza virus, or flu as it is more commonly known, tends to affect the nose, throat and occasionally the lungs.
There are three types of flu virus that infect humans:
- A viruses: They tend to be the cause of outbreaks in most years and are responsible for the global pandemics. They can infect humans and animals.
- B viruses: These cause less severe disease and are responsible for smaller outbreaks typically affecting humans.
- C viruses: Generally cause mild illness in humans and are not thought to cause flu epidemics.1
The fourth, D viruses mainly affects cattle and is not known to infect or cause illness in humans.
Influenza A viruses have two types of antigens on their surface.
- Haemagglutinin (H), the role of this antigen is to bind to the cells they are infecting, there are 18 different H subtypes.
- Neuraminidase (N), the N antigen allows the viruses to be released from an infected cell after replication, there are 11 different N subtypes.