Over-Reactive Immune System Kills Young Adults During Pandemic Flu

http://www.sciencedaily.com/releases/2010/12/101205202526.htm

ScienceDaily (Dec. 5, 2010) — A hallmark of pandemic flu throughout history, including the 2009 H1N1 pandemic, has been its ability to make healthy young and middle-aged adults seriously ill and even kill this population in disproportionate numbers. In a paper published Dec. 5 in Nature Medicine, Vanderbilt University Medical Center researchers provide a possible explanation for this alarming phenomenon of pandemic flu. The study's findings suggest people are made critically ill, or even killed, by their own immune response.

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But why did infants and the frail elderly escape this mechanism of death in the H1N1 pandemic?

"We found in 2009, the elderly had good immunity because they had seen a very similar virus sometime before 1957. Babies hadn't seen many viruses at all so there was no trigger. It came down to the young adults -- primed with an ineffective response. Their bodies already had defenses against previous influenza viruses that look like this one but weren't close enough," Polack said.

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