You probably can’t remember the first time you came down with the flu as a kid. But new evidence indicates that the human immune system never forgets its first encounters with an influenza virus, possibly even using that immunological “memory” to protect against future infections by novel strains of avian influenza, or bird flu.
In a study that looked at cases of bird flu in six countries in Asia and the Middle East between 1997 and 2015, an NIH-supported research team found that people born before 1968 were at lower risk of becoming seriously ill or dying from the H5N1 strain of the bird flu virus than were those born afterwards . Just the opposite was true of another emerging strain of bird flu. People born before 1968 were at greater risk of becoming seriously ill or dying of H7N9, while those born after that date were more often protected.
Why the switch? It turns out the H5N1 bird flu is more closely related to the seasonal influenza bug that predominated prior to 1968, after which two seasonal strains more closely related to H7N9 took over. This suggests one’s first experience with the flu and developing immunity can mean the difference between life and death decades later when exposed to a completely new flu strain.
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