Reply #106: The 1918 flu pandemic seemed to spare the very young and older adults.

[elocs]

http://www.huliq.com/11/72680/1918-spanish-flu-records-...

"In the 1918/19 pandemic, mortality was greatest among previously healthy young adults, when normally you would expect that elderly people would be the most likely to die,'' Professor Mathews says "We don't really understand why children and older adults were at lesser risk.

"One explanation may be that children were protected by innate immunity while older people may have been exposed to a similar virus in the decades before 1890 which gave them partial but long-lasting protection.

"Those born after 1890 were young adults in 1918. They did not have the innate immunity of children and as they weren't exposed to the pre-1890 virus they had little or no immunity against the 1918 virus. We can't prove it but it is a plausible explanation."

Another striking feature is that the pandemic appeared in three waves, in the summer and autumn of 1918 and then the following winter.

One theory being examined to explain why some people were only affected in the second or third wave is that because of recent exposure to seasonal influenza virus they had short-lived protection against the new pandemic virus.

"The attack rates in the big cities weren't as high and this is probably because many people had been exposed to ordinary flu viruses, giving short-lived immunity,'' he says.