Update on Influenza A H1N1 pdm09 virus (swine flu)

Influenza virus is a common human pathogen that causes serious respiratory illness and deaths. Influenza A viruses are further subtyped into 16 haemagglutinin (HA) types and 9 neuraminidase (NA) types. Influenza A viruses infect a variety of animals including humans, pigs, horses, sea mammals and birds. Due to the presence of segmented genome, Influenza A virus can undergo genetic reassortment in animals simultaneously infected by more than one subtypes of the virus, leading to evolution of new strains to which human beings are immunologically naïve. In April 2009, a new strain of Influenza virus A H1N1, commonly referred to as “swine flu,” began to spread in several countries around the world, and caused about 2,84,000 deaths globally. The pandemic strain Influenza A/H1N1/pdm09 affected people who had no contact with pigs indicating person to person transmission, and was not detected in nature in swine or birds. The strain can be diagnosed in the laboratory by various molecular methods like real time RT-PCR and rapid diagnostic tests. Influenza A/H1N1/pdm09 strain is resistant to adamantanes and is treated by oseltamivir or zanamivir. Killed and Live vaccines containing the current circulating types of influenza A and B viruses are available for protection against the virus.