They lurk on the kitchen sponge, your computer keyboard and the dirty laundry. Flush the toilet and they become airborne. Strangers leave them behind on airplanes, gas pumps, shopping carts, coffeeshop counters and elevator buttons. Your desktop, office microwave handles, and the exercise bike at the gym are covered with them. Don't even think about the toys at day-care centers or the kids' playground equipment.

Germs -- the microscopic bacteria, viruses, fungi and protozoa that can cause disease -- cling to the most common surfaces and then hitch a ride on our hands. As swine flu spreads from person to person around the world, it is most often being transmitted by coughing or sneezing, but it can also infect people who touch something with flu virus on it and then touch their mouth or nose, the Centers for Disease Control and Prevention warns. And like an unwelcome house guest, a flu virus can hang around for days.

No wonder germophobes -- including me -- are on high alert, viewing every surface as a potentially lethal petri dish. We're using our elbows to push elevator buttons, forgoing the handshake and social kiss for the fist bump, and fanatically disinfecting everything in sight. Sales of alcohol-based hand sanitizers were up nearly 17% as of the first week of September compared to the same period last year, according to Chicago-based research firm Information Resources. And marketers are taking full advantage of our paranoia, introducing anti-bacterial dishwasher-safe keyboards, machine-washable leather shoes, germ-resistant paper file folders and even hands-free communion wafer dispensers for churches.

But how vulnerable are we to the sea of germs swirling around us? Our immune system protects us from most of them, and in some spots that harbor germs, like household drains, the risk of transfer is low. Experts say there's no reason to panic -- even though there may be good reasons to be grossed out, since the spread of germs is often linked to poor bathroom hygiene and bacteria from human waste.

'We take in humongous amounts of live organisms every day, and we are all routinely covered in fecal organisms,' says Michael Bell, associate director for infection control at the Centers for Disease Control and Prevention's Division of Healthcare Quality Promotion. 'It's a testament to our body's own defenses -- if they routinely made us ill, none of us would have a chance.'

Even the scariest bugs can usually be vanquished through old-fashioned hand washing. 'Regardless of what you touch, make sure you clean your hands on a regular basis so you have a better chance of not delivering bacteria into your body through your mouth, nose and eyes or a cut on your skin,' Dr. Bell says. He advises thorough and frequent hand cleaning -- which may be needed 10 times or more daily depending on your activities -- with soap or alcohol-based hand sanitizer.

Cleaning and disinfecting things like desks and doorknobs can play a role in protecting us, he says, but 'focusing on one surface misses the point, because no surface is not germy.' （The CDC.gov Web site offers information on keeping germs at bay in the home, how to wash your hands correctly, and the importance of flu vaccines and other immunizations in preventing disease.）

Also, not all germs are harmful; we need friendly bacteria that live on our skin to help fight off bad bugs, and bacteria in our mouth and gut help digest our food and prevent illness and disease.

Still, I wanted to know where in my home, office and wider world I should most forcefully brandish my disinfectant wipes and hand-sanitizer. My calls to experts turned up some surprising culprits: the public toilet seats I'd always been warned about are likely cleaner than the desks in my workplace. My kitchen sponge and cutting board harbor the biggest dangers, as do places like elevator buttons, communal coffee carafes and gym equipment, that are touched by many hands and are rarely cleaned.

'We are sharing more surfaces than ever before in history, spending more time indoors, travelling on bigger planes and cruise ships and working in bigger office complexes,' says Charles Gerba, a microbiologist at the University of Arizona's Department of Soil, Water and Environmental Science. 'The biggest risks are in areas of high contact -- like the hundreds of people who have touched that escalator rail before you did.'

One of the scariest germ incubators may be the office. Your co-worker eating at the next cubicle isn't just annoying you with the smell of fried onions -- he's leaving behind particles of food that can be breeding ground for bacteria. Add in the microbes transferred from workers' hands to keyboards, phones and the computer mouse, and the average office desk is may harbor 400 times more germs than the average toilet seat, since office desks and surfaces may be rarely cleaned, while bathrooms tend to be disinfected regularly, Dr. Gerba says.

After testing surfaces and objects in 113 offices in five cities, the Arizona researchers found that women's offices had more than twice the bacteria of their male counterparts. Makeup cases, phones and purses had the highest number of bacteria; for men it was wallets, hand-held electronic devices and phones. Women's offices had higher numbers of mold and yeast, mostly from food kept in drawers. But the superbug MRSA, isolated in 6% of offices, was found more often in men's offices on the phone, computer mouse, desktop and the bottom of desk drawers.

The studies are funded by makers of disinfectants including Procter & Gamble and Clorox, whose products were also used to test the effectiveness of cleaning and compare regular cleaning regimens to disinfecting with substances like bleach. Dr. Gerba says more research is needed on the link between surface germs and disease, since it's impossible to say who will get sick.

'Some people will never get ill no matter what they do or don't do, and others will get ill almost every time,' he notes.

At home, the kitchen may be the germiest room. About 50% to 80% of food-borne illnesses happen in the home, where micro-organisms can be spread from raw meat and vegetables on chopping boards, utensils and counters, and then spread on hands. The culprits are dangerous bacteria such as e. coli, salmonella and campylobacter. They cause food-borne illnesses that strike 76 million people each year, sending 300,000 of them to the hospital and killing 5,000.

One problem is haphazard cleaning; a study by the U.K.-based Hygiene Council found that in 12% of cases, surfaces that looked clean in homes were heavily contaminated. Sponges and cleaning cloths can be swarming with bacteria from previous wipe-ups, so to be on the safe side, it's best to use paper towels, disposable cloths or reusable ones that have been decontaminated and dried, the group advises. The CDC advises microwaving sponges for 30 seconds or putting them in the dishwasher every other day or so depending on how often you use them.

In the laundry room, your average load of wash contains more than coffee stains. The Hygiene Council also warns it can be packed with bacteria such as e. coli from clothing, towels and linens. Washing in cold water doesn't kill the germs; if you have to wash at lower temperatures, add a laundry disinfectant. Wash your hands after loading the washing machine and dry clothes immediately, since bacteria and fungi build up on damp items, the group advises.

In the bathroom, the family toothbrush holder can also harbor bacteria; if you have to all share the same one, don't allow the brushes to touch each other, the CDC recommends. But it also says there is no evidence to support disinfecting toothbrushes in the microwave or with ultraviolet devices on the market. Best strategy: Get a new one every few months and rinse thoroughly after using.

And keep your toothbrush away from the commode -- especially the powerful flush of toilets on airplanes. Some studies have shown that flushing sends a spray of water containing bacteria that settles on people and surrounding surfaces.

In general, fecal particles are only worrisome if they've come from someone with intestinal illness or diarrhea, but the best advice I ever heard was to treat all airplane bathroom surfaces as if they are radioactive; keep the lid closed when flushing, use a paper towel to handle lid, faucets and door handles after washing hands, then use hand sanitizer once back at the seat as an extra precaution.

While surfaces are often the leading source of germs, remember germs can thrive in water we may inadvertently swallow at public swimming pools （don't ever get in one if you see a baby without a swim diaper） and waterparks （think of all those people who may not be diligent about personal hygiene）. Hotel hot tubs can be bubbling cauldrons of rash-causing Pseudomonas aeruginosa, as chlorine and other disinfectants evaporate more quickly in high temperatures. And communal showers may harbor foot fungus.

After reviewing all this depressing information, I turned to my own doctor, New York infectious disease specialist Eric Neibart, who helped bring me down to earth -- sort of. What are the chances of picking up an infectious disease from the germs we come in contact with daily?

'Millions of people touch things every day and nothing happens, so just use common sense,' Dr. Neibart advises. 'There's a bigger risk of being injured in a taxicab.'

它们潜伏在厨房的洗碗布上、你的电脑键盘和脏衣服上。冲完马桶后，它们还可以飞升到空气中。陌生人把它们留在飞机上、加油站、购物推车、咖啡馆柜台和电梯按钮上。你的台式电脑、办公室微波炉把手、健身房里的动感单车上都覆盖着它们。更别提日托中心的玩具，或是孩子操场上的器械了。

微生物──微观世界中能使人致病的细菌、病毒、真菌和原生动物──会附着在最常见的物体表面，然后会"搭便车"到我们的手上。美国疾病控制及预防中心（Centers for Disease Control and Prevention）警告说，在甲型H1N1流感在全球人群中传播之际，它最经常的是通过咳嗽或打喷嚏传播，不过也可能传染给那些接触了有流感病毒的物体之后又接触自己的嘴巴和鼻子的人。就像一位不受欢迎的访客一样，流感病毒可以很多天赖在那里。

难怪极端恐惧细菌的人（我就是一个）会高度戒备，把每个物体的表面都视为可能致命的细菌培养皿。我们用胳膊肘按电梯按钮，对首次见面的人避免行握手或亲吻礼，并且对看到的任何东西都疯狂地消毒。据位于芝加哥的研究公司Information Resources的数据，截至9月的第一周，含酒精的洗手液销量较去年同期增长了近17%.营销人士也在充分利用我们的疑神疑鬼，推出了可以用洗碗机清洗的抗菌键盘、可机洗的皮鞋、抗菌的文件夹、甚至还有不用手的教堂圣餐发放器。

不过，在我们周围汹涌澎湃的细菌海洋面前，人类到底有多脆弱呢？我们的免疫系统可以保护我们不受大部分细菌的侵犯，在一些细菌孳生的地方，比如家里的地漏，细菌传播的风险较低。专家们说，没有理由恐慌，不过注意还是应该的，原因是细菌的传播常常与厕所不干净和人体排泄物中的细菌有关。

疾病控制及预防中心医疗雷竞技百科 推广部传染病控制副主任贝尔（Michael Bell）说，我们每天会接触数不清的微生物，我们也通常会受到排泄物中微生物的包围。他说，这正好证明了人体自身有着防御系统，如果细菌总是让我们生病，没有人会有机会活下来。

就算是最恐怖的细菌通常也可以通过传统的洗手加以消除。贝尔说，不管你接触过什么东西，确保定时洗手，这样你就降低了通过嘴巴、鼻子、眼睛或皮肤伤口把细菌传播到体内的机会。他建议经常用肥皂或含酒精的洗手液彻底洗手，可能需要每日洗手10次甚至更多，这要取决于你的活动。

他说，清洁并为桌子和门把手等物体进行消毒在保护我们也发挥着作用，不过只专注于一个表面就错了，原因是任何表面都有细菌。（疾病控制及预防中心网站CDC.gov提供有关防止家里细菌传播，如何正确洗手，流感疫苗的重要性和其他防病的免疫措施等信息。）

此外，并非所有的细菌都对人体有害；我们的皮肤上需要有"友好"的细菌来帮助抵抗"坏"的细菌，口腔和肠胃里的细菌可以帮助我们消化食物，防止疾病。

不过，我希望知道我的家里、办公室和更广阔的世界里，有哪些地方我需要大力使用消毒纸巾和洗手液。我给专家打电话咨询后，发现了一些令人吃惊的问题：经常被警告要注意的公共厕所很可能比办公室里的桌子要干净。厨房里的洗碗布和切菜板存在最大的危险，同样，像电梯按钮、公共的咖啡壶和健身房器械也是如此，这些东西很多人都会接触，而很少清洁。

亚利桑那大学土壤、水和环境科学系微生物学家革巴（Charles Gerba）说，我们现在共同接触到的物体表面比以往任何时候都要多，在室内呆的时间更多，坐更大的飞机和游船出行，在更大的写字楼里办公。他说，风险最高的地方是那些有很多人接触的地方，比如在你之前有数百人都接触过的那个自动扶梯的扶手。

最让人恐怖的细菌培养器之一可能是你的办公室。在隔壁小间里吃东西的同事不仅是在用炸洋葱刺激你的嗅觉，他还留下了可以孳生细菌的食物残渣。革巴说，加上人把手上的细菌传播到了键盘、电话和电脑鼠标上，普通的办公桌孳生的细菌可能比普通马桶上的高400倍，原因是办公桌和表面可能很少被清洁，而卫生间往往会定期消毒。

在对5个城市113个办公室的表面和物品进行过化验后，亚利桑那大学的研究人员发现，女性办公室的细菌数量是男同事的两倍。化妆盒、电话和钱包的细菌数量最多；而男性则是钱包、手持电子设备和电话。女性办公室的霉菌和酵母菌数量较多，主要是来自抽屉中的食品。但在6%的办公室中发现的超级病菌葡萄球菌则更多出现于男性的办公室中，主要是在电话、电脑鼠标、电脑和抽屉的底部。

这些研究是由宝洁公司（Procter & Gamble）和高乐氏（Clorox）等消毒剂制造商资助的，它们消毒产品的有效性也被进行了测试，并将普通清洁方法与漂白剂等消毒方法进行了比较。革巴说，需要对表面细菌与疾病之间的联系进行更多的研究，因为不可能说明谁就会生病。

他说，有些人不管做什么或不做什么都永远不会生病，而有些人几乎每次都会生病。

在家里，厨房可能是细菌最多的地方。约有50%至80%的食物传播的疾病都发生在家里，微生物可以从菜板、盘子和案台上的生肉和蔬菜传播，然后传播到手上。罪魁祸首是那些危险的细菌，如大肠杆菌、沙门氏菌和弯曲杆菌。它们每年令7,600万人患上食物传染的疾病，使其中30万人到医院就诊，5,000人死亡。

一个问题是随意地清洁；英国的卫生理事会（Hygiene Council）进行的一项研究发现，在12%的情况下，看起来很干净的家居用品表面其实布满细菌。海绵和抹布可能附着了上次清洁时的细菌，所以为了安全起见，该组织建议，最好使用纸巾、一次性抹布或净化和烘干后可以重复使用的抹布。美国疾病控制及预防中心建议将海绵放到微波炉中消毒30秒，或每隔一天左右放到洗碗机中清洗，具体取决于你的使用频率。

在洗衣间，你每次洗涤的衣服中不仅仅包含咖啡污渍。卫生理事会警告说，其中可能还有来自衣服、毛巾和床单上的大肠杆菌等细菌。在冷水中洗涤并不能杀死病菌；如果你要在较低温度下洗涤，可以添加些衣物消毒剂。该组织建议，向洗衣机添加衣物后要洗手，并立即烘干衣服，因为细菌和真菌在潮湿物品上会大量繁殖。

在浴室中，牙刷架也会成为细菌的乐园；美国疾病控制及预防中心建议，如果你们使用同一个牙刷架，不要让牙刷彼此接触。但它也说，没有证据支持在微波炉或市面上销售的紫外线设备中对牙刷消毒。最好的策略：每几个月换一个新牙刷，并在使用后进行彻底清洗。

把牙刷放得离便桶远一些，尤其飞机上那种冲力很强的马桶。一些研究表明，冲厕所时飞溅的水花中带有细菌，会附着在人体和周围的物体上。

一般说来，只有患有肠道疾病或腹泻的人的粪便微粒才有害，但我听到的最佳建议是把所有飞机厕所的表面都视为具有放射性一样；冲水时盖上盖子，洗手后通过纸巾接触盖子、水龙头和门把手，然后回到座位上再使用洗手液作为额外预防措施。

虽然物体表面往往是细菌的主要来源，但要记住，细菌在我们可能无意中吞下的公众泳池（如果你在其中看到了没戴游泳尿布的婴儿，就千万不要进入）和水上乐园（想想所有那些可能不勤于个人卫生的人）的水中也大量存在。酒店的热水管上寄居了大量能引发皮疹的绿脓杆菌，因为氯和其他消毒剂在高温下挥发得更快。公共浴室可能会有足部真菌。

在研究了所有这些令人紧张的信息后，我求助于我的医生──纽约传染病专家内巴特（Eric Neibart）,他让我在某种程度上变得现实了一些。从我们日常接触的细菌中患上传染病的概率有多大？

内巴特建议，数百万人每天都会与病菌接触，但都安然无恙，所以只要按常识行事即可。与之相比，在出租车内受伤的概率反倒更大一些。