Cursing your sick colleague for the infection you can feel settling into your chest? You might want to aim the finger of blame closer to home.
It's entirely possible you may have infected yourself with whatever respiratory bug has latched onto your lungs. The same can be said about some of the stomach-wrenching gastrointestinal ailments people occasionally get.
That's because with a number of infections, people sometimes self-inoculate. They take germs they picked up on their hands when they were hanging onto bus poles or shaking a hand someone recently sneezed into and they deliver the bugs to places where those bugs can go from harmless to disease-causing.
In a nutshell, they stick germ-coated fingers into their mouths, they rub their eyes, they are even known to poke a finger into a nostril.
And voila! Bug on skin becomes bug on mucous membrane – a much more porous surface and an easier route to a warm and welcoming place for the bug to migrate toward.
Handwashing and alcohol gels can slough those germs off your fingers. And that's why public health officials repeat the handwashing mantra relentlessly, particularly during cold and flu season.
But a group of researchers suggests there's a part of the prevention equation that public health folks don't stress often enough: If you kept your fingers out of your mouth/nose/eyes, you'd lower your risk of self-inoculating.
"People touch their faces, touch their mouths, pick their noses and all of that. And in those behaviours they can bring these viruses that are on their hands to the muscosa ... where they can really infect us," says Wladimir Alonso, an infectious diseases researcher at the U.S. National Institutes of Health's Fogarty International Center.
Alonso and some colleagues wrote a letter to the Journal of Infectious Diseases recently to make the point.
They had done a small study where they observed 249 randomly selected individuals in public spaces in Florianopolis, Brazil and on the Washington subway system. The individuals they observed touched common surfaces and their mouth and nose area at a rate of 3.3 and 3.6 touches respectively an hour.
Their point? Handwashing alone can't keep up with the infection potential of self-inoculation events. Or as they put it, "the opportunities for hand recontamination in public settings occurs at a much higher rate than any viable handwashing frequency."
They suggest public health campaigns should also teach people about how they infect themselves by touching their mucous membranes, so they become more aware of the role these behaviours could play in acquiring infection.
Dr. Jody Lanard likes the suggestion. A risk communications expert based in Princeton, N.J., Lanard monitors public health messaging about influenza closely, and says officials often overstate the benefits of handwashing.
That's not to say Lanard doesn't believe in handwashing. She is in fact a big fan of the practice. But she'd prefer it if authorities stuck to the science – and says there isn't that much evidence handwashing cuts down on flu transmission. (That doesn't mean it doesn't, just that there aren't a lot of studies showing that it does. Studies aimed at answering this kind of question can be devilishly hard to do.)
Lanard thinks public health messaging should suggest that it's plausible that frequent handwashing reduces the risk of acquiring colds and the flu. "I love that word plausible. It covers up a whole lot of lack of good evidence."
And she says the idea of telling people about self-inoculation makes sense, because there are times when people simply cannot wash their hands, such as during a commute on public transit.
The author of a book on hygiene says public health messages about handwashing and self-inoculation should be synergistic. "I don't think it's an either-or thing," says Dr. Bonnie Henry, author of Soap and Water and Common Sense.
Henry is the medical director of communicable disease prevention and control services at the British Columbia Centre for Disease Control. She says it can be difficult to get people to think about self-inoculation.
"It doesn't resonate so much when you say 'Don't do something' that people aren't really conscious of doing in many cases," she says.
"Making them aware of it is important. But I think it's inevitable that you're going to touch your face and you really need to make sure that you clean your hands regularly because that's what's going to protect you at the end of the day."
"I always say 'It's not having bugs on your hands that's the issue. It's when you go to eat your sandwich or rub your eye. That's when you're going to get sick from it.' So I think the two messages have to go together."