Fear of swine flu is fading, but there are still plenty of reasons to wash your hands frequently.

　　The list of infections that can spread via unwashed hands reads like the Biblical plagues, including staph, strep, salmonella, E. coli, hepatitis, MRSA (methicillin-resistant Staphylococcus aureus), colds, flu and norovirus -- the infamous cruise-ship bug.

　　The importance of hand washing has been known since 1847, when a doctor named Ignaz Semmelweis suspected that maternity patients were dying in his Vienna hospital because med students treated them right after working on cadavers. When he instituted hand-cleaning, the deaths fell sharply.

　　The Centers for Disease Control and Prevention says hand washing is the most effective way to stay healthy. But many people don't do it often enough, or long enough, to be effective. Here's a guide:

　　-- When to do it. Wash your hands every time you use the bathroom. Every surface presents an opportunity for germs to hitchhike out. 'Who thinks to clean the latch on the inside of the stall door? Try nobody,' says Jim Mann, executive director of the Handwashing for Life Institute, which advises food-service providers around the world on best hand-hygiene practices.

　　Also wash your hands whenever you change a diaper, pick up animal waste, sneeze, cough or blow your nose; when you take public transportation, insert or remove contact lenses, prepare food, handle garbage and before eating. Few people are as conscientious as they should be. Mr. Mann recalls being in meetings to discuss hand hygiene: 'Everybody shakes hands. You finish the talk, and everybody runs for the food line. Nobody washes their hands.'

　　-- How to do it. Soap and water is the gold standard. In a recent study in the journal Clinical Infectious Diseases, researchers in Australia doused the hands of 20 health-care workers with human H1N1 flu virus. Soap and water removed slightly more virus than three alcohol-based hand rubs. When volunteers didn't clean their hands, most of the virus was still present an hour after exposure.

　　It's the mechanical process of washing that's so effective. Soap molecules surround and lift the germs, friction from rubbing your hands loosens them, and water rinses them down the drain.

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