Janet Napolitano, the new Director of Homeland Security, moved quickly with the Centers for Disease Control to declare a public health emergency to deal with the emerging new swine flu. Current reports state that the flu virus may have killed more than 80 people in Mexico and sickened hundreds more.
Usually, a swine flu passes from pigs to humans, but not from person to person. What's novel about this strain of virus is that it is made up of material from pig, avian and human viruses. In addition, this virus is sickening the young and the healthy. Scientists indicate that such bugs are notorious for their ability to evolve from mild to severe, but they are not yet able to address its lethality. Napolitano moved quickly because of the novel nature of the virus--a crucial condition for starting a pandemic flu.
Two locations for further information are Science Base and a brief by Gautam Naik and Betsy McKay in Monday's Wall Street Journal.