How Bad Was the 2009 H1N1 Epidemic?

The hubbub surrounding pandemic 2009 H1N1 “swine” flu has died down, soon to be replaced, no doubt, with a similar 2010 version. Meanwhile, just how severe was 2009 H1N1 epidemic influenza compared with ordinary seasonal flu?

Researchers evaluated symptomatic residents in a cluster of Wisconsin zip codes during three periods in 2008–2009, including the summer and fall of 2009 when pandemic 2009 H1N1 was circulating but before the vaccine was widely available. The 545 participants with culture-confirmed pandemic 2009 H1N1 were on average much younger than the 632 people with seasonal influenza A H3N2 (median age, 10 vs. 25 years), but about the same age as the 221 people with seasonal (nonpandemic) H1N1. Symptoms were similar in all groups, a…