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.

Experts recommend using warm water -- mainly for comfort, so you'll wash longer. Use liquid soap if possible. Bar soaps can harbor germs.

Use enough soap to build a lather. Lace your fingers together to cover all the surfaces. Rub the fingertips of one hand into the palm of the other, then reverse. Keep rubbing for as long as it takes to sing 'Happy Birthday' twice. (Some experts prefer 'Row, Row, Row Your Boat.' But any tune will do as long as it lasts at least 15 seconds.)

Rinse thoroughly. Residual soap can make hands sore. Leave the water on while you grab a paper towel and use it to shut off the faucet. Take it with you to use on the door handle as well.

-- Drying lessons. Many hand-hygiene experts are down on hand dryers -- chiefly because few people have the patience to dry completely and end up wiping their hands on their clothes. Air dryers can also blow remaining germs as far as six feet away.

-- Antibacterial soap? In 2005, a Food and Drug Administration panel voted 11-to-1 that antibacterial soaps are no more effective at keeping people healthy than regular soap. There may be some downside too. Some antibacterial ingredients like triclosan leave a residue on the skin that continues killing some bacteria. Critics worry that the remaining bacteria could become resistant, not only to soap but also to antibiotics. 'To our knowledge, it's not happened, but it's theoretically possible,' says Elaine Larson, a professor in the schools of nursing and public health at Columbia University.

-- Hand sanitizers. It's not often that a personal-care product gets a presidential endorsement. Some drug stores sold out after Barack Obama echoed the CDC's recommendation that people use alcohol-based hand sanitizers when soap and water aren't available to help stop the spread of swine flu.

Experts say they must be at least 60% alcohol to kill germs. 'Alcohol ruptures their cell membranes -- it causes them to explode,' says Dr. Larson.

Curiously, the FDA does not allow over-the-counter hand sanitizers to claim they kill viruses. The CDC's recommendations are based on information published since the FDA ruling, says Nicole Coffin, a CDC spokeswoman.

Can you overdo handwashing? Yes. 'Try to strike a balance between being obsessive-compulsive and being reasonable,' says Dr. Larson. 'And if there is some kind of outbreak like with the flu or SARS, then there is reason for more caution.'

甲型H1N1流感引发的担忧正在日渐消退，不过勤洗手的理由仍有很多。

能通过没洗的手进行传播的传染病就像《圣经》中的埃及十灾一样多：包括葡萄球菌、链球菌、大肠杆菌、肝炎、抗药性金黄葡萄球菌、感冒、流感和诺如病毒──即臭名昭著的常在游船上爆发的病毒。

从1847年开始，人们就已经认识到了洗手的重要性，当时维也纳一位名叫塞麦尔维斯(Ignaz Semmelweis)的医生怀疑，他医院中孕妇死亡的原因是医学生在处理过尸体后马上就医治孕妇。当他下了洗手令之后，死亡率大幅降低。

美国疾病控制预防中心表示，洗手是保持健康的最有效方法。不过很多人洗手不够勤、洗的时间不够长，所以并没有起到作用。下面就介绍一下正确的洗手方法：

何时洗手。每次上完厕所后都要洗手。每个表面都可能为病菌的传播提供机会。手部卫生研究机构Handwashing for Life Institute的执行董事吉姆•曼(Jim Mann)说，有谁想到要清洁卫生间门内侧的插销吗？肯定没人想到过。这个机构为全球食品服务提供商提供保持手部卫生的建议。

有关甲型H1N1流感病毒的报道占据了各大媒体的头条，并且使人们再次意识到洗手的重要性。健康专栏作家Melinda Beck介绍了怎样洗手才能洗掉病菌，预防传染病的传播。每次换尿布、拣拾动物粪便、打喷嚏、咳嗽或是擤鼻涕后都要洗手。乘坐公共交通、戴或是摘隐形眼镜、准备食物、处理垃圾或是吃饭前也都要洗手。很少有人对此足够注意。曼回忆说，有一次在手部卫生研讨会上，所有的人都在握手，你讲完后，所有人都去取食物，没人洗手。

如何洗手。肥皂和水是黄金标准。在《临床传染病》(Clinical Infectious Diseases)期刊上最近登载的一篇研究报告中，澳大利亚的研究人员把20名医护人员的手浸在人类H1N1流感病毒中。肥皂和水去除的病毒略多于三种含酒精的手部消毒液。当志愿者们不洗手时，大部分病毒一个小时之后仍然存在。

产生如此效果的是洗手的机械过程。肥皂分子包围并把细菌拉起来，双手的摩擦使细菌脱离皮肤，然后水把它们冲入下水道。

专家们建议使用温水，主要是因为这会舒服一点儿，你会洗得久一些。如果可能的话，使用洗手液。肥皂能孳生细菌。

多用一些肥皂，洗出泡沫。双手手指交叉，把所有的皮肤表面都洗到。把一只手的指尖在另一只手的手掌里搓洗，反过来再做一遍。这样反复搓洗，时间要可以唱两遍《生日快乐歌》。（一些专家更喜欢《划船歌》，不过什么歌都可以，只要至少洗15秒钟。）

冲洗干净。残余的肥皂会让手痛。洗完后不要关水龙头，用纸巾擦完手后垫着纸巾把水龙头关掉。拿着这片纸巾，握门把手的时候还要用到。

如何弄干。很多手部卫生专家不建议使用干手器，主要是因为很少有人有耐性把手完全吹干，最后只是在衣服上擦擦了事。干手器还能把残余的细菌吹到最远6英尺的地方。

抗菌肥皂？2005年，美国食品和药物管理局(FDA)一个小组以11：1的票数表决，抗菌肥皂在保持人体健康上并不比普通肥皂更有效。或许还有一些弊病。一些抗菌成分（比如三氯沙）能残留在皮肤上继续杀菌。批评人士担心残留下来的细菌可能会产生抗药性，不只是对肥皂而且是对抗菌素。哥伦比亚大学护理及公共卫生学院教授伊兰•拉森(Elaine Larson)说，据我们所知，还没有发生这样的事，不过理论上讲是可能的。

手部消毒液。个人护理产品获得总统的支持可不常见。美国疾病控制预防中心建议，在弄不到肥皂和水来防止甲型H1N1流感的传播时，要使用含酒精的手部消毒液。当奥巴马总统响应这一建议后，一些药店都售磬了。

专家们说，手部消毒液必须至少有60%的酒精成分才能杀菌。拉森说，酒精能破坏细菌的细胞膜，导致细菌破裂。

奇怪的是，美国食品和药物管理局不允许非处方手部消毒液产品宣称有杀菌作用。美国疾病预防控制中心发言人尼科尔•考芬(Nicole Coffin)说，该机构的建议是根据美国食品和药物管理局上述决定发布后公布的信息做出的。

洗手可能会过度吗？是的。拉森说，要在强迫症式和合理程度的洗手之间达到平衡。如果爆发了某种疫情，比如流感或是非典型肺炎，那么应该更加小心。