What Is H5N1 strain of Bird Flu?
All flu viruses are classified as type A, B or C depending on their structural arrangement. Type A is responsible for lethal pandemics and is found in both animals and humans. Type B causes local outbreaks of flu. Type C is the most stable of the three and infected people show only mild symptoms of flu. Type B and C are usually found only in humans. Type B and C are more stable than type A and are not classified according to their subtypes. Influenza viruses of type A are divided into subtypes and the naming is done on the basis of two proteins (antigens) found on their surface – Hemagglutinin (HA) and Neuraminidase (NA). Sixteen types of HA and nine types of NA exist. Thus a total 144 combinations are possible. Thus H5N1 is a type A virus and gets its name from HA 5 protein and NA 1 protein present on its surface.
