Statistics show that the flu virus can spread from person to person without the flu showing symptoms
A study carried out by researchers from Imperial College London found that a flu virus could spread before any symptoms show. 3 ferrets were infected with the 2009 H1N1(Swine flu) strand and found that they were able to spread the virus to other ferrets before they developed symptoms.
Researchers caged 3 pre-symptomatic ferrets with the other infected ferrets. All 3 became infected before any symptoms of the initial ferrets showed. The ferrets seemed to be most infected and had the highest viral levels 24 hours after they had been infected, even though they didn’t develop symptoms until later on in the day.