Childhood infections provide lifelong protection against flu viruses from animals

https://www.eurekalert.org/pub_releases/2016-11/uoc--cip110716.php

Public Release: 10-Nov-2016
Childhood infections provide lifelong protection against flu viruses from animals
UCLA, Arizona researchers explain that birth year may largely determine people's risk for serious illness in an influenza pandemic
University of California - Los Angeles

Exposure to influenza viruses during childhood gives people partial protection for the rest of their lives against distantly related influenza viruses, according to a new study in the journal Science.

Scientists from UCLA and the University of Arizona analyzed data from all known human cases of two types of avian influenza -- more than 1,400 people in all -- and found evidence of previously unrecognized human immunity against several viruses that circulate in animals but have not previously circulated in humans. They also discovered that people born before 1968 are more susceptible to certain viruses, while people born during or after that year are more at risk for different strains of the flu.

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The researchers can now predict with reasonable precision whether a person will have immunity against new influenza strains based on their birth year, which indicates the seasonal flu virus that was most likely to have caused their first flu infection during childhood.

"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. "These results will help us quantify the risk of particular emerging influenza viruses sparking a major outbreak."

It is unclear whether that imprinting provides strong enough immunity to prevent infection altogether, but it substantially reduces the risk for severe disease, the study reports. People born in "protected" birth years were much less likely to get sick enough to visit the doctor, be hospitalized or die from H5N1 or H7N9 infections.

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