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流感引發的擔憂正在日漸消退，不過勤洗手的理由仍有很多。

能通過沒洗的手進行傳播的傳染病就像《圣經》中的埃及十災一樣多：包括葡萄球菌、鏈球菌、大腸桿菌、肝炎、抗藥性金黃葡萄球菌、感冒、流感和諾如病毒──即臭名昭著的常在游船上爆發的病毒。

從1847年開始，人們就已經認識到了洗手的重要性，當時維也納一位名叫塞麥爾維斯(Ignaz Semmelweis)的醫生懷疑，他醫院中孕婦死亡的原因是醫學生在處理過尸體后馬上就醫治孕婦。當他下了洗手令之后，死亡率大幅降低。

美國疾病控制預防中心表示，洗手是保持健康的最有效方法。不過很多人洗手不夠勤、洗的時間不夠長，所以并沒有起到作用。下面就介紹一下正確的洗手方法：

何時洗手。每次上完廁所后都要洗手。每個表面都可能為病菌的傳播提供機會。手部衛生研究機構Handwashing for Life Institute的執行董事吉姆•曼(Jim Mann)說，有誰想到要清潔衛生間門內側的插銷嗎？肯定沒人想到過。這個機構為全球食品服務提供商提供保持手部衛生的建議。

有關甲型H1N1流感病毒的報道占據了各大媒體的頭條，并且使人們再次意識到洗手的重要性。健康專欄作家Melinda Beck介紹了怎樣洗手才能洗掉病菌，預防傳染病的傳播。每次換尿布、揀拾動物糞便、打噴嚏、咳嗽或是擤鼻涕后都要洗手。乘坐公共交通、戴或是摘隱形眼鏡、準備食物、處理垃圾或是吃飯前也都要洗手。很少有人對此足夠注意。曼回憶說，有一次在手部衛生研討會上，所有的人都在握手，你講完后，所有人都去取食物，沒人洗手。

如何洗手。肥皂和水是黃金標準。在《臨床傳染病》(Clinical Infectious Diseases)期刊上最近登載的一篇研究報告中，澳大利亞的研究人員把20名醫護人員的手浸在人類H1N1流感病毒中。肥皂和水去除的病毒略多于三種含酒精的手部消毒液。當志愿者們不洗手時，大部分病毒一個小時之后仍然存在。

產生如此效果的是洗手的機械過程。肥皂分子包圍并把細菌拉起來，雙手的摩擦使細菌脫離皮膚，然后水把它們沖入下水道。

專家們建議使用溫水，主要是因為這會舒服一點兒，你會洗得久一些。如果可能的話，使用洗手液。肥皂能孳生細菌。

多用一些肥皂，洗出泡沫。雙手手指交叉，把所有的皮膚表面都洗到。把一只手的指尖在另一只手的手掌里搓洗，反過來再做一遍。這樣反復搓洗，時間要可以唱兩遍《生日快樂歌》。（一些專家更喜歡《劃船歌》，不過什么歌都可以，只要至少洗15秒鐘。）

沖洗干凈。殘余的肥皂會讓手痛。洗完后不要關水龍頭，用紙巾擦完手后墊著紙巾把水龍頭關掉。拿著這片紙巾，握門把手的時候還要用到。

如何弄干。很多手部衛生專家不建議使用干手器，主要是因為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。干手器還能把殘余的細菌吹到最遠6英尺的地方。

抗菌肥皂？2005年，美國食品和藥物管理局(FDA)一個小組以11：1的票數表決，抗菌肥皂在保持人體健康上并不比普通肥皂更有效。或許還有一些弊病。一些抗菌成分（比如三氯沙）能殘留在皮膚上繼續殺菌。批評人士擔心殘留下來的細菌可能會產生抗藥性，不只是對肥皂而且是對抗菌素。哥倫比亞大學護理及公共衛生學院教授伊蘭•拉森(Elaine Larson)說，據我們所知，還沒有發生這樣的事，不過理論上講是可能的。

手部消毒液。個人護理產品獲得總統的支持可不常見。美國疾病控制預防中心建議，在弄不到肥皂和水來防止甲型H1N1流感的傳播時，要使用含酒精的手部消毒液。當奧巴馬總統響應這一建議后，一些藥店都售磬了。

專家們說，手部消毒液必須至少有60%的酒精成分才能殺菌。拉森說，酒精能破壞細菌的細胞膜，導致細菌破裂。

奇怪的是，美國食品和藥物管理局不允許非處方手部消毒液產品宣稱有殺菌作用。美國疾病預防控制中心發言人尼科爾•考芬(Nicole Coffin)說，該機構的建議是根據美國食品和藥物管理局上述決定發布后公布的信息做出的。

洗手可能會過度嗎？是的。拉森說，要在強迫癥式和合理程度的洗手之間達到平衡。如果爆發了某種疫情，比如流感或是非典型肺炎，那么應該更加小心。