The claim: Roughly 1 in 5 people are infected by some form of the flu each winter, but only 23% of those infected show any symptoms, according to a UK study appearing in The Lancet. That’s cause for concern, because even if you’re symptom free, you still may be capable of spreading influenza to others.
[sidebar]The research: Researchers from the University College London tracked reported flu cases among 5,448 people from 2006 to 2011. They also contacted the study participants weekly during cold and flu seasons to ask about any symptoms, and collected blood samples and nasal swabs to check for influenza infections that may have gone unnoticed. Here’s what they found: Flu infection rates were roughly 22-times higher than the government had estimated, and 3 out of 4 infected people didn’t report any symptoms.