First of all we should try and explain what influenza (flu) is. There are three main types: A, B and C, with B and C only infecting humans and influenza A being able to infect humans, animals and birds. The surface of each influenza A virus contains two types of protein, neuraminidase (N), of which there are nine types, and haemagglutinin (H), of which there are sixteen types. Consequently, there are lots of sub-strains of the influenza A virus and they are given names depending on the type of proteins found on the surface. Examples of these sub-strains could be H1N1, H1N2 and H2N3.

Another characteristic of the A strain is that it has the ability to produce new strains – in other words, mutate. It is as these new strains occur that new types of flu are discovered.

Bird flu is a strain of influenza A that affects birds, of which all species can be affected. Whereas wild birds can carry the disease when they migrate, they don’t usually become ill with it whereas poultry birds like turkeys and chickens do become ill. The virus spreads easily between these birds.

Bird Flu

It is the H5N1 virus that is causing all the problems with humans at the moment. This strain has affected birds for almost half a century, but it mutated back in 1997 in the Far East and spread to humans. As of yet this strain of the virus cannot be transferred from human to human, only from bird to bird or sometime bird to human.