(KFVS) - Brace yourself: flu season is upon us.
For some that could mean using up sick days and a lot of sniffles.
Others might barely be touched.
New research sheds some light on why this might be.
Researchers at the University of Arizona and UCLA, found your birth year predicts — to a certain extent — how likely you are to get seriously ill or die in an outbreak of an animal-origin influenza virus.
The main takeaway: if you were exposed to a certain strain of the flu virus as a kid, your body most likely developed a way to fight it off, meaning you would be less likely to come down with that version of the flu.
That first exposure reduces your risk of a future severe infection by up to 75 percent, according to the team of researchers.
"Our findings show clearly that this 'childhood imprinting' gives strong protection against severe infection or death from two major strains of avian influenza," said James Lloyd-Smith, a UCLA professor of ecology and evolutionary biology and the study's senior author.
To figure this out, researchers studied two avian-origin influenza A ("bird flu") viruses, H5N1 and H7N9.
These two viruses have already caused hundreds of spillover cases of severe illness or death in humans.
However, these viruses are typically only found in wild birds and poultry, not humans.
In the future, though, they could mutate, which would allow them to jump from birds into humans.
If that happened, the flu viruses would spread rapidly between humans.
The year 1968
The key year is 1968.
Researchers call this the diving line.
People born during and after 1968 are more likely to have protection against H7N9, which is more closely related to the 1968 virus than to flu viruses that circulated before.
Those born before 1968 are likely to have protection against H5N1.
"These findings challenge the current paradigm, where the entire population would be immunologically defenseless in a pandemic caused by a novel influenza virus," Gostic said. "Our results suggest it should be possible to forecast age distributions of severe infection in future pandemics, and to predict the potential for novel influenza viruses from different genetic groups to cause major outbreaks in the human population."
What about vaccines?
"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," Michael Worobey said, a University of Arizona professor of ecology and evolutionary biology.
Worobey said in the future doctors will need to figure out possible ways to modify our immunological imprinting with a vaccine.
At this point, the Center for Disease Control says getting an annual flu vaccine is the best way to protect yourself and your family from the flu.
This year the flu vaccine was updated to match circulating flu viruses, including H1N1 and H3N2.
Only injectable flu shots are recommended this season.