The genesis and source of the H7N9 influenza viruses causing human infections in China.

A novel H7N9 influenza A virus first detected in March 2013 has since caused more than 130 human infections in China, resulting in 40 deaths. Preliminary analyses suggest that the virus is a reassortant of H7, N9 and H9N2 avian influenza viruses, and carries some amino acids associated with mammalian receptor binding, raising concerns of a new pandemic. However, neither the source populations of the H7N9 outbreak lineage nor the conditions for its genesis are fully known.

Innate immune responses to influenza A H5N1: friend or foe?

Avian influenza A H5N1 remains unusual in its virulence for humans. Although infection of humans remains inefficient, many of those with H5N1 disease have a rapidly progressing viral pneumonia that leads to acute respiratory distress syndrome and death, but its pathogenesis remains an enigma. Comparison of the virology and pathogenesis of human seasonal influenza viruses (H3N2 and H1N1) and H5N1 in patients, animal models and relevant primary human cell cultures is instructive.