By Robert Preidt
THURSDAY, Nov. 10, 2016 (HealthDay News) -- The year you were born could help predict your risk of becoming seriously ill or dying after exposure to a flu virus that jumped from animals to humans, researchers suggest.
It was believed that previous exposure to a flu virus offered people little to no protection against new animal-origin flu viruses, according to investigators from the University of Arizona in Tucson and the University of California, Los Angeles.
But an analysis of all-known cases of severe illness or death caused by the H5N1 and H7N9 bird flu viruses showed that the first infection with flu virus as child helps determine which new bird flu viruses people would be protected against in the future.
Depending on when people were born, they were infected with different types of flu viruses for the first time as children, the researchers explained. This causes their bodies to produce different types of flu-fighting antibodies.
As an analogy, "let's say you were first exposed to a human 'orange lollipop' flu as a kid," said co-senior author Michael Worobey. "If later in life you encounter another subtype of flu virus, one from a bird . . . that your immune system has never seen before but whose proteins also are of a similar 'orange' flavor, your chances of dying are quite low because of cross-protection," he said. Worobey is head of the department of ecology and evolutionary biology at the University of Arizona.
"But if you were first infected with a virus from the 'blue lollipop' group as a kid, that won't protect you against this novel, 'orange' strain," he explained in a university news release.
If you do get infected with a strain you had as a child, the researchers estimated that there is a 75 percent protection rate against severe disease, and an 80 percent protection rate from flu death.
The findings could lead to new ways to reduce the risks of major flu outbreaks. The next step is to determine exactly how a child's first bout of the flu affects the immune system and possible ways to modify it with a vaccine, the researchers said.
"In a way it's a good-news, bad-news story. 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," Worobey said.
"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 of flu strains," he added.
The study was published in the Nov. 11 issue of the journal Science.