Study: Warm water as good as soap scrub
BY JIM SHAMP, The Herald-Sun
March 10, 2005
CHAPEL HILL -- A research study published Thursday by infection control specialists at UNC Hospitals indicates that rubbing your hands together for at least 10 seconds under plain ol' warm tap water cleans them just as effectively, in occasional washing, as the expensive specialty soaps and cleansers sold to hospitals and medical clinics.
The UNC researchers tested 14 hand hygiene agents plus tap water against specific bacteria and viruses applied to the hands of 62 adult volunteers.
The water worked wonders.
"Based on these findings, I'd put my hands in my mouth after routine sink washing for 10 seconds," said Emily Sickbert-Bennett, a public health epidemiologist with the UNC Health Care System and the UNC School of Public Health. She's lead author of the study, conducted as part of her UNC public health master's degree work from 2000 to 2002 and published in the March issue of the American Journal of Infection Control.
The study volunteers' hands were cleaned and then contaminated in oversized rubber gloves filled with a solution containing Serratia marcescens and MS2 bacteriophage. Those are, respectively, a harmless bacterium and a "non-enveloped" virus comparable to, but substituted for, its cousins that cause such scourges as hepatitis A, acute gastroenteritis and the common cold. Sickbert-Bennett said flu virus is even less hardy than these bugs, so any cleansing method capable of wiping out the test virus is almost certain to be even more effective against flu.
After the contamination, the scientists had the subjects re-clean their hands at different times with 104-degree warm water, with various soap-and-water combinations and with other agents such as alcohol wipes and hand-cleaning gels. Then the researchers swabbed the volunteers' hands, placed the swabbed bugs in culture and measured their populations.
Other researchers have conducted tests showing the importance of frequent hand cleansing, especially among health care workers who can easily spread serious diseases among their patients if they don't use caution. But most studies have had volunteers scrub for at least 30 seconds at a time. The UNC study is the first to look at 10-second scrubs, because the researchers found that to be the average length of time UNC health care personnel actually devote to the process.
Anti-microbial agents were good for eliminating about 90 percent of the bacteria on hands, Sickbert-Bennett said. But waterless, alcohol-based hand rubs didn't fare well against viruses and tended to lose their effectiveness when used multiple times in succession without thorough water washing, according to the report.
"We believe that the physical removal of the bacteria and viruses from the hands is what's at work here," said Sickbert-Bennett. And some of the anti-microbials in hand wash agents made them more effective over time -- for instance after 10 episodes of washing and contamination, those containing chlorhexidine gluconate got better.
Though the study measured the relative bug-killing abilities of hand-washing approaches, "we don't know what level is required to stop disease transmission," said Sickbert-Bennett. "Maybe removal of 90 percent of these organisms is needed for avoiding infections, or maybe only 50 percent is required. Different organisms have different infectious doses. And efficacy is only one part of hand cleaning. Compliance is another huge part -- and that comes from how much people like the product and how easy it is to use."
William Rutala, a co-author of the paper, said the findings are important because health-care associated infections rank in the top five causes of death, killing some 90,000 people a year in the United States.
Besides Sickbert-Bennett, the paper's authors include Rutala and David Weber, professors of medicine and epidemiology at the UNC schools of medicine and public health; Mark Sobsey, professor of environmental sciences and engineering in public health; and medical technologist Maria Gergen-Teague. Gregory Samsa, a Duke University biostatistician, helped analyze the data.
