MicrobeWorld

Influenza A viruses typically cause severe respiratory disease mainly in the very young or the elderly. The 2009 swine-origin H1N1 virus is unusual because it preferentially infects individuals under 35 years of age. We’ve previously noted that being older is a good defense against 2009 H1N1 influenza virus, in part because older people have antibodies that block infection. Experiments done in mice show that immunization with 1918-like or classical H1N1 swine influenza viruses protects against infection with 2009 H1N1 virus.