The Lancet, 2009

The emergence in Mexico in April of a new strain of influenza A H1N1 (swine flu) capable of causing human disease and of person-to-person transmission has put health authorities around the world on alert for an influenza pandemic, and caused a storm of coverage in the mass media.
Outside Mexico, the disease caused by H1N1 appears no more severe than seasonal influenza; however, the possibility that the virus might cause more severe disease as it spreads cannot be discounted. Cases of infection have now been confirmed in 33 countries on four continents. WHO is considering raising the pandemic alert level to six, which would signify the first influenza pandemic since 1968.

Go to the Lancet H1N1 Flu Resource Centre here.