Buzz
That sneeze you just heard in the elevator, the germs on the handrail from an hour ago, and that coworker who refuses to stay home, breathing all over you. Cold and flu viruses are everywhere, and if you're coming down with something, you're likely passing it on too.
"There's proof that you start shedding the [flu] virus before any symptoms appear," says Dr. Pat Salber, a San Francisco-based emergency room internist. For instance, studies involving ferrets (who can catch and spread human flu) show that they can infect others in nearby cages even before showing signs like adorable ferret sneezes.
You're most contagious about three days after catching the flu virus, usually the first or second day of symptoms. If you're following common sense (and your company's sick leave policy is sensible), you'll likely be resting at home by then. But you can still spread the virus even if your immune system is fighting it off successfully. A study from the UK Flu Watch cohort discovered that 77 percent of flu-infected individuals had no symptoms. So, the person who infected you might be someone you least expected.
For most people, the flu remains contagious for roughly a week. By the time you're starting to feel better, you're probably not spreading virus particles everywhere, according to Dr. Salber. You may still be a little contagious, but doctors typically don't consider you a major risk. "Usually—like now, with so much flu going around—you’re likely not the only one spreading it." (Wonderful.)
The influenza virus is one of the most well-researched, but the details may vary based on the specific illness you're dealing with and how your immune system is responding to it. Other viruses that cause colds are less studied.
It’s not just about sneezing: Virologist Ian Mackay points out that research suggests some people may transmit colds and flu just through regular breathing. While these studies mostly focus on flu and RSV (a more serious cold virus), it seems likely that we spread a variety of viruses this way. "[This research is] broadly applicable to all 200+ respiratory viruses," he states.
And about that handrail covered in snot? Mackay observes that we touch surfaces and then our faces about three to four times every hour. He suggests: "Avoiding touching your face until after washing your hands is a healthy habit to adopt."
