NEWS - Three-quarters of people with seasonal and pandemic flu have no symptoms

Around 1 in 5 of the population were infected in both recent outbreaks of seasonal flu and the 2009 H1N1 influenza pandemic, but just 23% of these infections caused symptoms, and only 17% of people were ill enough to consult their doctor ...

http://medicalxpress.com/news/2014-03-three-quarters-people-seasonal-p