Image: Warner Brothers

I recently saw the movie Contagion, in which a ruthless, jet-setting, flu-like virus kills millions of people in a matter of weeks and causes global hysteria. The movie makes spreading the disease look as easy as:
1. Sick person coughs on folder.
2. Healthy person handles same folder.
3. Healthy person touches their face and--bam! Turns into dead man walking.

In a post-bird flu, post-swine flu world, we kind of knew that's how the transmission process works, but seeing Gwyneth keel over made us wonder how we might avoid that fate—or the common cold.

Surface-to-person contagion is technically called fomite transmission, says Anna Bowen, MD, MPH, a medical epidemiologist who works for the Centers for Disease Control and Prevention.  "Generally, germs can live on surfaces for minutes to hours to days, depending on the nature of the germ and the surface." Smooth surfaces transmit viruses better than porous ones.

This is why the CDC is always reminding us to wash our hands. But we wanted to know--is a simple soap-and-water combo better than anti-bacterial gels at protecting us from Voldemort-like viruses?

Hand-washing, it turns out, is still the best line of defense. First, the surfactant in soap lifts the germs from your hands, then the vigorous rubbing motion physically pushes them away, and finally, the water washes them down the drain. By contrast, anti-bacterial gels and foams use alcohol to kill the germs. "Killing germs is much harder task than washing them away," says Bowen, and there are some types of germs that are resistant to alcohol.

Gels and foams are a good back-up plan, she says. One thing to note: They're more effective if your hands aren't covered in dirt or oil (which makes the alcohol's germ-zapping power less effective).

Bottom line: Hand-washing has been proven to be more effective than hand-sanitizing when it comes to preventing the transmission of salmonella, the norovirus, and parasitic organisms like giardia and cryptosporidium. Some data suggest that it may help prevent the spread of the flu, as well.

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