The swine flu outbreak of 2009-2010 may have killed 15 times more people worldwide than originally estimated, according the U.S. Centers for Disease Control and Prevention.
A study, published this morning in the London-based journal Lancet Infectious Diseases, said the toll was closer to 284,500 people—not the 18,500 estimated by the World Health Organization at the time, based on laboratory testing. In fact, it might have been as high as 579,000 people.
Additionally, CDC researchers confirmed that the H1N1 influenza virus killed an unusually high number of young people—80 percent of victims were under 65 years of age.
By the time the WHO declared an end to the pandemic in August 2010, H1N1 had been reported in more than 214 countries. More than half the deaths may have been in southeast Asia and Africa, rather than the 12 percent of officially reported fatalities, the authors of the CDC study wrote.
In an editorial published along with the study in the journal, Cecile Viboud of the National Institutes of Health and Lone Simonsen of George Washington University wrote that the new estimate showed the difficulty in tracking the effects of a pandemic as it was unfolding. The WHO pointed out at the time that it had grossly underestimated the toll, mainly because many victims lacked access to medical systems and went uncounted, and because the H1N1 virus was not always detectable after a victim died.