2009-2010 H1N1

Outbreaks of influenza cases in North America reported in April 2009 were identified as new strain and quickly spread around the world. By the end of the month, the WHO had declared the outbreak a PHEIC, and by June it was a worldwide pandemic. This strain affected younger people more severely than most other flu viruses. Mitigation efforts included closing schools for up to 14 days where cases were detected, as well as widespread use of antiviral treatments and prophylactics, though drug-resistant strains of the virus soon emerged. Vaccine clinical trials began in July, several vaccines were approved by September, and widespread vaccination began in December. The WHO declared the pandemic officially over in August 2010. Total case and death counts are uncertain, as many cases may have gone unreported. By some estimates, up to 575,000 died worldwide, with 60.8 million cases and over 12,000 deaths occurring in the United States.