Scientists Discover Adults Only Catch the Flu Twice a Decade

Do you think that you have the flu? Odds are, you're wrong about that. Researchers have discovered that adults over the age of 30 only catch the flu about twice a decade.

Flu-like illnesses can be caused by many pathogens. This makes it difficult to assess how often people are infected by influenza. In order to determine the amount of people infected by the flu, the researchers analyzed blood samples from volunteers in Southern China. They looked at antibody levels against nine different strains that circulated from 1968 to 2009.

So what did they find? While children get flu on average every other year, this becomes less frequent as they grow older. In fact, from the age of 30 onwards, flu interactions tend to occur at a steady rate of just two per decade.

"There's a lot of debate in the field as to how often people get flue, as opposed to flu-like illness caused by something else," said Adam Kucharski, one of the researchers, in a news release. "These symptoms could sometimes be caused by common cold viruses, such as rhinovirus or coronavirus. Also, some people might not realize they had flu, but the infection will show up when a blood sample is subsequently tested. This is the first time anyone has reconstructed a group's history of infection from modern-day blood samples."

The findings may help scientists take into account the effect of immunity in the population. More specifically, they may help researchers make better predictions on how the virus will change in the future.

"What we've shown in this study is to analyze how a person's immunity builds up over a lifetime of flu infections," said Kucharski. "This information helps us understand the susceptibility of the population as a whole and how easy it is for new season strains to spread through the population."

The findings are published in the journal PLOS Biology.

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