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Germ-phobic Americans have become the world's number one consumers of hand sanitizers. Disturbed by reports of flu epidemics, sick and tired of getting sick and tired from colds, and alarmed by reports of especially virulent strain of Australian norovirus that causes stomach flu, some Americans use hand sanitizers 5, 10, and even 20 times a day.
But do they work? Let's take a look at the lineup of hand sanitizers versus soap and water for getting rid of Norwalk virus, an especially nasty cause of a condition known as viral gastroenteritis, or winter stomach flu.
Viral Infection Spread By the Fecal-Oral Route
The Norwalk virus was named for the town of Norwalk, Ohio, where it was first detected after a massive epidemic of winter vomiting occurred among school children at Bronson Elementary School in 1968.
If you get any kind of "stomach flu" in the United States, there is a 90% chance that you came down with the illness after you were exposed to Norwalk virus. (Technically speaking, the term "norovirus" should refer to a broader group or genus of viruses, but Norwalk virus is the only species of virus identified in the genus, so the terms can be used interchangeably.)
Norwalk virus is transmitted by the fecal-oral route. If you get feces, or vomit, from a person who is infected with the virus into your mouth, you almost certainly will get the disease. It only takes about 20 copies of the virus to cause an infection. (Scientists say that the strain of the virus going around during the winter of 2012-2013 in Australia and the United States just requires 12 copies of the virus to cause an infection.) That is an almost unimaginably small amount of the virus, so how in the world could anyone avoid it. It turns out that keeping hands clean works for preventing the infection.
Hand Sanitizers versus Soap and Water for Norwalk Virus
Researchers at the schools of public health at Emory University in Atlanta and North Carolina State University in Raleigh tested the hand sanitizers against plain old soap and water for getting Norwalk virus off the hands of students who volunteered for the study. They started by diluting feces they collected for a student who had had the disease, and then they asked the study volunteers to get their hands contaminated by the diluted feces solution, cleansing them with antibacterial soap, regular soap and water, or water alone.
The results of the study were more than a little surprising:
- Cleansing hands with alcohol-based hand sanitizer got rid of no more than 50% of the virus, leaving a high likelihood of infection.
- Cleansing hands with liquid soap and water got rid of more than 90% of the virus, still not enough to prevent infection.
- Cleansing hands under running water for 15 seconds (long enough to sing "Happy Birthday to You" or "Row, Row, Row Your Boat") got rid of up to 99% of the virus, enough to prevent infection.
Dipping your hands in sodium hypochlorite (Clorox) would have been even more effective for getting rid of the virus, but really hard on your skin. Don't try it. But the most effective way to get rid of the world's most common stomach flu virus turned out to be purely mechanical, rinsing it down the drain, not trying to kill it with chemicals. What about bacteria that are transmitted by the fecal-oral route.