In late March 2009, two kids living more than 100 miles apart in Southern California came down with the flu. By mid-April, their illnesses had been diagnosed as being caused by a new strain of H1N1 influenza, aka swine flu. Flu outbreaks that had started a few weeks earlier in Mexico were soon ascribed to the new H1N1 as well. On April 25, with cases confirmed or suspected in 19 Mexican states and five U.S. ones, the World Health Organization declared the disease’s spread a “Public Health Emergency of International Concern.”
Swine flu has a history that makes health authorities pay special heed. In 1918, a variant of H1N1 influenza caused a global pandemic that is estimated to have killed as many as 50 million people, or 2.7% of the world’s population. After tests found H1N1 in two soldiers during a flu outbreak at the Fort Dix army base in New Jersey in 1976, the U.S. government jumped into action, with President Gerald Ford announcing a plan to vaccinate “every man, woman, and child in the United States.” That turned into something of a debacle, though, as the virus didn’t seem to spread beyond Fort Dix and the hastily assembled vaccine killed about 30 people.