The year of your birth could decide whether you live or die in the next big flu pandemic

Women from the Department of War took 15-minute walks to breathe in fresh air to ward
off the influenza virus during World War.
'Your first infection sets you up for either success or failure in a huge way'.

The year of your birth could determine whether you live or die in a major flu pandemic, such as the 1918 outbreak that killed an estimated 50 million people worldwide, according to new research.

Virulent new strains of the disease have periodically jumped from animals to humans over the centuries with devastating results, raising concern about new outbreaks in pigs and chickens, for example. The last week has seen reports of bird flu in Germany, Austria, Hungary and several other countries, prompting the authorities to set up 'protection zones' and slaughter infected birds.

But extreme forms of virus gradually evolve to become less deadly because strains that do not kill their host spread more easily. The human flu around today can be a serious disease but it is essentially a relatively mild echo of the past.

Now a new study, published in the journal Science, has found the flu people are first exposed to as a child plays a major role in setting up the human immune system to defend against one of just two main types.

One of the researchers, Professor Michael Worobey, head of Arizona University’s Department of Ecology and Evolutionary Biology, 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. 

“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.”

After the first infection, the immune system makes antibodies designed to target a lollipop-shaped protein that sticks out of the flu virus.

There are 18 different types of lollipop, but the researchers said there were just two main ‘flavours’.

“In this analogy, let's say you were first exposed to a human ‘orange lollipop’ flu as a kid,” Professor Worobey said. 

“If later in life you encounter another subtype of flu virus, one from a bird and one that your immune system has never seen before but whose proteins also are of a similar ‘orange’ flavour, your chances of dying are quite low because of cross-protection. 

“But, if you were first infected with a virus from the ‘blue lollipop’ group as kid, that won’t protect you against this novel, ‘orange’ strain.”