Among the viruses soapy hand washing flushes down the drain is the one that causes the common cold. Other removable viruses cause hepatitis A, acute gastroenteritis and a host of other illnesses.

　　A separate key finding was that waterless handwipes only removed roughly 50 percent of bacteria from volunteer subjects?hands.

　　"We studied the efficacy of 14 different hand hygiene agents in reducing bacteria and viruses from the hands," said Emily E. Sickbert-Bennett, a public health epidemiologist with the University of North Carolina Health Care System and the UNC School of Public Health. "No other studies have measured the effectiveness in removing both bacteria and viruses at the same time."

　　For the first time, too, the UNC researchers tested what happened when people cleaned their hands for only 10 seconds, Sickbert-Bennett said. That represented the average length of time researchers observed busy health-care personnel washing or otherwise disinfecting their hands at work.

　　"Previous studies have had people clean their hands for 30 seconds or so, but that's not what health-care workers usually do in practice, and we wanted to test the products under realistic conditions," she said.

　　Anti-microbial agents were best at reducing bacteria on hands, but waterless, alcohol-based agents had variable and sometimes poor effects, becoming less effective after multiple washes, Sickbert-Bennett said. For removing viruses from the hands, physical removal with soap and water was most effective since some viruses are hardy and relatively resistant to disinfection.

　　Researchers first had volunteers clean their hands and then contaminated their hands with Serratia marcescens and MS2 bacteriophage. Those are, respectively, a harmless bacterium and virus comparable to, and substituted for, disease-causing organisms. After that, scientists had the subjects clean their hands with various agents and measured how much of the bacteria and virus remained afterwards.