Study Finds at Least One in Five Humans Contracted H1N1 in 2009

Posted on January 25, 2013

Scientists estimate that at least one in five people were infected in the first year of the 2009 H1N1 pandemic. The findings come from a joint study led by the World Health Organization and Imperial College London. Data from 19 countries, including China, India, U.K. and U.S., was analyzed. The study was published here in the journal, Influenza and Other Respiratory Viruses.

The highest rates of infection were found in children and the lowest infection rate was in older adults. 47% of children aged 5 to 19 were infected, while just 11% of adults aged 65 or older contracted the virus.

H1N1 infected a large percentage of the human population. Fortunately, the mortality rate was very low. The CDC reports that in the U.S. it had a mortality rate of 1.5 fatalities per 100,000 population. The ease with which the virus spread around the globe shows how dangerous influenza would be with a higher fatality rate, such as the 1918 influenza outbreak, where there was an abnormally death rate in young healthy people. The 1918 virus killed about 1% of people infected in the 25 to 34 age group. Another chart showed it killed about 3% of people aged 25 who contracted it in the U.S., which is highly unusual.

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