Avian Influenza (Bird Flu) in Humans: Recent Scenario

are further classified into subtypes on the basis of the two main surface glycoproteins hemagglutinin (HA) and neuraminidase (NA). Influenza A subtypes and B viruses are further classified by strains. Avian influenza virus can be distinguished as Low Pathogenic Avian Influenza (LPAI) and Highly Pathogenic Avian Influenza (HPAI) forms based on genetic features of the virus and the severity of the illness they cause in poultry. Influenza virus A is usually responsible for bird flu (Avian influenza) but same time also responsible for pandemics of influenza in humans. Out of hundreds of strains of avian influenza A viruses, only four are capable to produce infection in humans: H5N1, H7N3, H7N7 and H9N2. Out of these, highly pathogenic avian influenza, H5N1strain is of greatest concern for human infection. This virus has affected poultry flocks and other birds in more than 50 countries. Total 309 laboratory-confirmed cases of avian influenza infection in humans have been reported to the World Health Organization between end of December 2003 to end of May 2007; out of which 187 deaths were confirmed. While human cases remain relatively rare and are largely the result of direct virus transmission from infected birds, a few cases of human-to-human transmission have been reported. But still there is a matter of great assurance that, H5N1strain does not easily cross from birds to infect humans. Oseltamivir is the first orally active antiviral drug used in the treatment and prophylaxis of influenza