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Your Birth Year May Determine Your Flu Risk

Your Birth Year May Determine Your Flu Risk

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By    |   Friday, 11 November 2016 11:45 AM

Scientists have always wondered why some people are hit harder – or even killed – by the flu, but a new study finds that the year you were born may hold the key to this mystery.

Until now, it was believed that previous exposure to a flu virus conferred little or no immunological protection against new influenza viruses that can jump from animals into humans.

But this new study finds that the year you were born may predict your risk of falling seriously ill – or even dying – in an influenza pandemic.

Researchers from the University of Arizona in Tucson, Ariz., and the University of California, Los Angeles conducted the study, which focused two avian-origin influenza A ("bird flu") viruses, H5N1 and H7N9, each of which already has caused hundreds of spillover cases of severe illness or death in humans.

Both strains are of global concern because they might at some point gain mutations that allow them not only to readily jump from birds into humans, but also spread rapidly between human hosts.

Analyzing data from every known case of severe illness or death from influenza caused by these two strains, the researchers discovered that whichever human influenza strain a person happened to be exposed to during his or her first infection with flu virus as a child determines which novel, avian-origin flu strains they would be protected against in a future infection.

This effect of "immunological imprinting" appears to be exclusively dependent on the very first exposure to flu virus encountered in life – and difficult to reverse, the researchers say.

The results provide a functional explanation for a pattern that had vexed epidemiologists for a long time: Why are certain age groups more likely than others to suffer serious or even fatal complications from an infection with novel influenza strains, the researchers say.

“If either of these viruses were to successfully jump from birds into humans, we now know something about the age groups that they would be hit the hardest," says Dr. Michael Worobey, head of the University of Arizona’s Ecology and Evolutionary Biology department and the study’s co-author.

This discovery could help in the development of a universal flu vaccine, and also help to curb the risks of a major flu outbreak, adds Worobey.

"Even a comparatively weak, mild pandemic flu event like the 2009 H1N1 (swine flu) outbreak is a trillion-dollar affair. A major pandemic like the one we saw in 1918 has the potential to kill large numbers of people and shut down the world's economy,” he adds.

But the findings, which appear in Science, also indicate how problematic creating a universal vaccine might be, he says.

"In a way it's a good-news, bad-news story," says Worobey.

"It's good news in the sense that we can now see the factor that really explains a big part of the story: Your first infection sets you up for either success or failure in a huge way, even against 'novel' flu strains.” But, he adds, “The bad news is the very same imprinting that provides such great protection may be difficult to alter with vaccines.

“A good universal vaccine should provide protection where you lack it most, but the epidemiological data suggest we may be locked into strong protection against just half of the family tree,” he says.
 

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Your birth year may predict how likely you are to get seriously ill – or even die – during a flu outbreak, a new study finds.
Flu, Influenza, vaccine, pandemic, risk
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2016-45-11
Friday, 11 November 2016 11:45 AM
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