In fact, the year you were born – to an extent – dictates how likely you are to survive an outbreak of animal-origin influenza.
Until now it was believed that previous exposure to a flu virus passed on little immunological protection against viruses that jump from animals to humans.
But these findings showed that the key is in your first ever childhood exposure to flu. It is in this one instance that your body creates “imprinting” antibodies to protect against future infections.
The team offer an analogy with sweets: if you were given an orange lollipop as a child, then later in your life you encounter another similar orange flavour, your chances of this affecting you are quite low.
Whereas if you first had a blue lollipop first time, you won’t be defended against the orange one.
Michael Worobey said: “In the lollipop analogy, people born before the late 1960s were exposed to ‘blue lollipop’ influenza as children (H1 or H2). The researchers found that these older groups rarely succumb to avian H5N1 ― which shares a ‘blue’ hemagglutinin ― but often die from ‘orange’ H7N9.”
Worobey thinks that a similar process may explain the unusual mortality patterns caused by the 1918 flu pandemic, which was more deadly among young adults.
“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. The bad news is the very same imprinting that provides such great protection may be difficult to alter with vaccines,” said Worobey.