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.'

    它們潛伏在廚房的洗碗布上、你的電腦鍵盤和臟衣服上。沖完馬桶后，它們還可以飛升到空氣中。陌生人把它們留在飛機上、加油站、購物推車、咖啡館柜臺和電梯按鈕上。你的臺式電腦、辦公室微波爐把手、健身房里的動感單車上都覆蓋著它們。更別提日托中心的玩具，或是孩子操場上的器械了。

    微生物──微觀世界中能使人致病的細菌、病毒、真菌和原生動物──會附著在最常見的物體表面，然后會"搭便車"到我們的手上。美國疾病控制及預防中心（Centers for Disease Control and Prevention）警告說，在甲型H1N1流感在全球人群中傳播之際，它最經常的是通過咳嗽或打噴嚏傳播，不過也可能傳染給那些接觸了有流感病毒的物體之后又接觸自己的嘴巴和鼻子的人。就像一位不受歡迎的訪客一樣，流感病毒可以很多天賴在那里。

    難怪極端恐懼細菌的人（我就是一個）會高度戒備，把每個物體的表面都視為可能致命的細菌培養皿。我們用胳膊肘按電梯按鈕，對首次見面的人避免行握手或親吻禮，并且對看到的任何東西都瘋狂地消毒。據位于芝加哥的研究公司Information Resources的數據，截至9月的第一周，含酒精的洗手液銷量較去年同期增長了近17%.營銷人士也在充分利用我們的疑神疑鬼，推出了可以用洗碗機清洗的抗菌鍵盤、可機洗的皮鞋、抗菌的文件夾、甚至還有不用手的教堂圣餐發放器。

    不過，在我們周圍洶涌澎湃的細菌海洋面前，人類到底有多脆弱呢？我們的免疫系統可以保護我們不受大部分細菌的侵犯，在一些細菌孳生的地方，比如家里的地漏，細菌傳播的風險較低。專家們說，沒有理由恐慌，不過注意還是應該的，原因是細菌的傳播常常與廁所不干凈和人體排泄物中的細菌有關。

    疾病控制及預防中心醫療質量推廣部傳染病控制副主任貝爾（Michael Bell）說，我們每天會接觸數不清的微生物，我們也通常會受到排泄物中微生物的包圍。他說，這正好證明了人體自身有著防御系統，如果細菌總是讓我們生病，沒有人會有機會活下來。

    就算是最恐怖的細菌通常也可以通過傳統的洗手加以消除。貝爾說，不管你接觸過什么東西，確保定時洗手，這樣你就降低了通過嘴巴、鼻子、眼睛或皮膚傷口把細菌傳播到體內的機會。他建議經常用肥皂或含酒精的洗手液徹底洗手，可能需要每日洗手10次甚至更多，這要取決于你的活動。

    他說，清潔并為桌子和門把手等物體進行消毒在保護我們也發揮著作用，不過只專注于一個表面就錯了，原因是任何表面都有細菌。（疾病控制及預防中心網站CDC.gov提供有關防止家里細菌傳播，如何正確洗手，流感疫苗的重要性和其他防病的免疫措施等信息。）

    此外，并非所有的細菌都對人體有害；我們的皮膚上需要有"友好"的細菌來幫助抵抗"壞"的細菌，口腔和腸胃里的細菌可以幫助我們消化食物，防止疾病。

    不過，我希望知道我的家里、辦公室和更廣闊的世界里，有哪些地方我需要大力使用消毒紙巾和洗手液。我給專家打電話咨詢后，發現了一些令人吃驚的問題：經常被警告要注意的公共廁所很可能比辦公室里的桌子要干凈。廚房里的洗碗布和切菜板存在最大的危險，同樣，像電梯按鈕、公共的咖啡壺和健身房器械也是如此，這些東西很多人都會接觸，而很少清潔。

    亞利桑那大學土壤、水和環境科學系微生物學家革巴（Charles Gerba）說，我們現在共同接觸到的物體表面比以往任何時候都要多，在室內呆的時間更多，坐更大的飛機和游船出行，在更大的寫字樓里辦公。他說，風險最高的地方是那些有很多人接觸的地方，比如在你之前有數百人都接觸過的那個自動扶梯的扶手。

    最讓人恐怖的細菌培養器之一可能是你的辦公室。在隔壁小間里吃東西的同事不僅是在用炸洋蔥刺激你的嗅覺，他還留下了可以孳生細菌的食物殘渣。革巴說，加上人把手上的細菌傳播到了鍵盤、電話和電腦鼠標上，普通的辦公桌孳生的細菌可能比普通馬桶上的高400倍，原因是辦公桌和表面可能很少被清潔，而衛生間往往會定期消毒。

    在對5個城市113個辦公室的表面和物品進行過化驗后，亞利桑那大學的研究人員發現，女性辦公室的細菌數量是男同事的兩倍。化妝盒、電話和錢包的細菌數量最多；而男性則是錢包、手持電子設備和電話。女性辦公室的霉菌和酵母菌數量較多，主要是來自抽屜中的食品。但在6%的辦公室中發現的超級病菌葡萄球菌則更多出現于男性的辦公室中，主要是在電話、電腦鼠標、電腦和抽屜的底部。

    這些研究是由寶潔公司（Procter & Gamble）和高樂氏（Clorox）等消毒劑制造商資助的，它們消毒產品的有效性也被進行了測試，并將普通清潔方法與漂白劑等消毒方法進行了比較。革巴說，需要對表面細菌與疾病之間的聯系進行更多的研究，因為不可能說明誰就會生病。

    他說，有些人不管做什么或不做什么都永遠不會生病，而有些人幾乎每次都會生病。

    在家里，廚房可能是細菌最多的地方。約有50%至80%的食物傳播的疾病都發生在家里，微生物可以從菜板、盤子和案臺上的生肉和蔬菜傳播，然后傳播到手上。罪魁禍首是那些危險的細菌，如大腸桿菌、沙門氏菌和彎曲桿菌。它們每年令7,600萬人患上食物傳染的疾病，使其中30萬人到醫院就診，5,000人死亡。

    一個問題是隨意地清潔；英國的衛生理事會（Hygiene Council）進行的一項研究發現，在12%的情況下，看起來很干凈的家居用品表面其實布滿細菌。海綿和抹布可能附著了上次清潔時的細菌，所以為了安全起見，該組織建議，最好使用紙巾、一次性抹布或凈化和烘干后可以重復使用的抹布。美國疾病控制及預防中心建議將海綿放到微波爐中消毒30秒，或每隔一天左右放到洗碗機中清洗，具體取決于你的使用頻率。

    在洗衣間，你每次洗滌的衣服中不僅僅包含咖啡污漬。衛生理事會警告說，其中可能還有來自衣服、毛巾和床單上的大腸桿菌等細菌。在冷水中洗滌并不能殺死病菌；如果你要在較低溫度下洗滌，可以添加些衣物消毒劑。該組織建議，向洗衣機添加衣物后要洗手，并立即烘干衣服，因為細菌和真菌在潮濕物品上會大量繁殖。

    在浴室中，牙刷架也會成為細菌的樂園；美國疾病控制及預防中心建議，如果你們使用同一個牙刷架，不要讓牙刷彼此接觸。但它也說，沒有證據支持在微波爐或市面上銷售的紫外線設備中對牙刷消毒。最好的策略：每幾個月換一個新牙刷，并在使用后進行徹底清洗。

    把牙刷放得離便桶遠一些，尤其飛機上那種沖力很強的馬桶。一些研究表明，沖廁所時飛濺的水花中帶有細菌，會附著在人體和周圍的物體上。

    一般說來，只有患有腸道疾病或腹瀉的人的糞便微粒才有害，但我聽到的最佳建議是把所有飛機廁所的表面都視為具有放射性一樣；沖水時蓋上蓋子，洗手后通過紙巾接觸蓋子、水龍頭和門把手，然后回到座位上再使用洗手液作為額外預防措施。

    雖然物體表面往往是細菌的主要來源，但要記住，細菌在我們可能無意中吞下的公眾泳池（如果你在其中看到了沒戴游泳尿布的嬰兒，就千萬不要進入）和水上樂園（想想所有那些可能不勤于個人衛生的人）的水中也大量存在。酒店的熱水管上寄居了大量能引發皮疹的綠膿桿菌，因為氯和其他消毒劑在高溫下揮發得更快。公共浴室可能會有足部真菌。

    在研究了所有這些令人緊張的信息后，我求助于我的醫生──紐約傳染病專家內巴特（Eric Neibart）,他讓我在某種程度上變得現實了一些。從我們日常接觸的細菌中患上傳染病的概率有多大？

    內巴特建議，數百萬人每天都會與病菌接觸，但都安然無恙，所以只要按常識行事即可。與之相比，在出租車內受傷的概率反倒更大一些。