What does the H & N stand for in avian influenza viruses?
As described by the World Health Organization, the letters “H” and “N” stand for haemagglutinin and neurominidase, two proteins found in the molecule of the influenza virus. Currently, scientists have recognized 16 HA subtypes and 9 NA subtypes. It appears that the antigens can join in any combination with one H and one N. The H antigen is responsible for binding the virus to the uninfected cells, and the N antigen determines how easily and quickly the virus spreads to uninfected cells. Though the subtypes of influenza virus that infect animals do not typically infect human beings, some viruses can mutate and become virulent in humans. The viruses vary in pathogenicity, though to date, all highly pathogenic outbreaks have been caused by influenza A virus subtypes H5 and H7. http://www.who.int/mediacentre/factsheets/avian_influenza/en/ You mentioned there has been one reported and confirmed case of human-to-human-to-human transmission. Did any infected persons die? In May 2006, the Worl
