The five-year flu

Though most people likely feel flu-like symptoms more often, adults catch a true flu virus about once every five years, a field study in China finds.

For the study, recently published in the journal PLoS Biology, an international team tested blood samples from 151 volunteers ages 7 to 81 to monitor how often they were infected with nine main strains of flu known to be circulating the globe between 1968 and 2009, according to BBC News. The research team discovered that, while children got the flu about once every other year, the infections became less frequent with age. Once someone was more than 30 years old, they contracted the flu about twice a decade.

The researchers noted that the findings may not apply to all populations, as the “exact frequency of infection will vary depending on background levels of flu and vaccination.”