Why is Swine Flu virus called H1N1?

The swine flu virus swept through Pune this July and here is a feature that looks at the phenomenon retrospectively and reflects on the prospects of such epidemics in future.

It is called H1N1 - H stands for haemagglutinin and N stands for neuraminidase - two proteins found on the virus. Haem-agglutinin helps the virus to attach itself and gain entry into to our cells. The virus replicates itself in large numbers there. Neuraminidase helps these newly formed viruses to come out of our cells.

There are many variations of these proteins in influenza viruses. In fact scientists have identified 16 types of hemagglutinins and 9 types of neuraminidases. 144 different combinations are possible...

Naming the virus by number of the subtype of the two proteins became a convention that allows unique name to all these types of influenza viruses. Bird flu that swept the world a few years earlier is another, called H5N1.

Influenza viruses infect many birds and mammals. Quite often, humans in contact with such birds or animals also get infected. But it is rare that the virus then moves from human to human. In such occasional cases, we see a sudden epidemic of Influenza in human societies. The swine flu which swept through Pune in July was just such a case. 

Quick identification of the type of influenza virus is useful to create a vaccine in response to an epidemic. But the vaccine would not be useful later because these viruses undergo rapid changes through both genetic drift as well as genetic shifts -

abrupt changes in their genome.

In most cases, the flu is self limiting Our immune system comes to the rescue and we would be alright in a few days. Symptomatic treatment of the fever and malaise is also often used, to reduce the suffering. In some rare cases, anti retroviral drugs and neuraminidase inhibitors are also used.