Because the 2009 H1N1 virus caused the most serious morbidity and mortality in those aged younger than 65 years, a substantial number — about 9.9 million — of life years were lost, according to calculations from the CDC. Researchers from the CDC examined data on 2009 H1N1 symptomatic attack rates and fatality ratios from a number of countries to calculate the median ranges of lower respiratory tract mortality rates in each WHO region and mortality stratum in the first year of virus circulation. Based on their calculations, they estimated that 249,000 (90% CI, 48,000-716,000) 2009 H1N1 deaths occurred globally, according to a presentation at the IDSA 49th Annual Meeting.
“Estimated 2009 H1N1 respiratory mortality was at least twofold higher than reported laboratory-confirmed deaths, and lower resource countries were disproportionately affected,” the researchers wrote in their abstract. Most of the deaths (58%) occurred in Africa and Southeast Asia. The researchers estimated that about 216,000 of the deaths (87%) occurred in those aged younger than 65 years, resulting in an estimated 9.9 million (90% CI 3,933,000-18,820,000) years of life lost.
The researchers concluded although estimated mortality may have been lower than that of some prior pandemics, the majority of 2009 H1N1 deaths were in persons less than 65 years, resulting in a substantial number of years of life lost.