Don’t count on alcohol-based hand sanitizer to protect against the flu. A Japanese study in mSphere, the journal of the American Society for Microbiology, found that it took nearly four minutes for hand sanitizer to completely deactivate influenza A virus (IAV) that had been mixed with mucus and dabbed on volunteers’ fingertips.
The findings are in contrast to the general recommendation by the CDC and World Health Organization to apply hand sanitizer for only 20 to 30 seconds. As the researchers noted, the alcohol in hand sanitizer is unable to penetrate the viscous mucus that the virus is encased in, at least when the mucus is still wet. Use of hand sanitizer on infected but dried mucus did deactivate the virus within 30 seconds, however.
“Until the mucus has completely dried, infectious IAV can remain on the hands and fingers, even after appropriate antiseptic hand rubbing,” the lead author stated in a press release.
The flu virus is most frequently transmitted through respiratory droplets expelled from the nose and mouth of infected people, but contact with the virus from surfaces (including hands) may also be a route for infection. That means that keeping your hands clean by washing them under running water with soap for at least 20 seconds is important—and effective—for preventing illness. For flu prevention, you should of course also get the flu shot every year.