Via Physician’s First Watch, the Centers for Disease Control estimates that 22 million people contracted H1N1 during the six months between mid-April and mid-October this year.

Of the 22 million, nearly 100,000 were hospitalized and 3,900 died, according to the CDC. Most of the deaths — 2,900, were adults between 18 and 64. Among children under 18, 540 died, as did 440 people older than 64.

The government also announced that, commencing news, data it releases about the epidemic will be based on estimates from the CDC’s Emerging Infection Program, rather than counting confirmed laboratory cases — presumably because the data from laboratories has become too large to process quickly.

Sourcing from Physician’s First Watch:
• CDC estimates of cases, hospitalizations, and deaths (Free)
• MMWR article on influenza surveillance (Free)
• MMWR article on vaccine effectiveness (Free)
• CDC news briefing transcript (Free)
• FDA news release on H1N1 vaccine approval for children (Free)
• NEJM/Journal Watch H1N1 Influenza Center (Free)