Are you one of those hosts who's immediately gripped by this conundrum¹ as your guests step across the threshold into your home: Should you, or shouldn't you, ask them to remove their shoes?

客人跨进家门的时候，你是否也纠结过这个难题：应不应该让他们脱鞋呢？

On the one hand, it makes you look like a fussy² host. On the other, what about the legions of disease-causing bacteria that will gleefully leap off their shoes and inevitably³ infest⁴ your home?

一方面，这让你看起来像个挑剔的主人。另一方面，如果大量的致病细菌大踏步地随着鞋子进入你家，并开始滋生，可怎么办呢？

Avoiding bacterial⁵ invasion at the risk of a little social awkwardness seems like a no-brainer. But are shoe bacteria something we should really be worried about in our homes? Here's what science tells us about how to navigate⁶ this conundrum.

冒着一点社交尴尬的风险来避免细菌入侵，这似乎是一个挺容易的选择题。但是，我们真的需要担心鞋子带进家里的细菌吗？下面来看看科学家是如何破解这个难题的。

To start with, there's no point in sugarcoating the pill: the average shoe harbors "hundreds of thousands of bacteria per square inch," according to Jonathan Sexton, an environmental microbiologist and research specialist at the University of Arizona.

首先，没有必要掩饰事实：美国亚利桑那大学环境微生物学研究专家乔纳森·塞克斯顿表示，普通的鞋子上“每平方英寸有数十万的细菌”，The soles of our shoes are essentially⁷ a meet and greet for these microbes, and with each step we take, we pick up new attendants. "Pretty much wherever you go, you're going to be picking up stuff," Sexton told Live Science. (Beware, however: Some places like bathrooms do harbor more bacteria and a greater diversity, he said.)我们的鞋底通常都聚集着大量的细菌，我们每迈出一步，鞋底都会粘上新的细菌。塞克斯顿告诉趣味科学网站说：“不管你去哪里，鞋底都会粘上细菌。”（但要注意的是，浴室等地方的细菌更多，种类也更多。）But exactly what types of bacterial communities are hanging out on our shoes, and do they pose a legitimate⁸ health threat?

那么，我们的鞋底粘的是到底是哪种细菌？它们对我们有健康危害吗？

Well, previous studies have shown that almost all shoes in some research samples were coated with fecal bacteria, including one prominent bug called Escherichia coli (E.coli), which researchers discovered on 96 percent of shoe soles. While many types of E.coli are harmless to humans, some strains can cause severe diarrhea, urinary tract⁹ infections and even meningitis.

此前的研究显示，在一些研究样本中，几乎所有鞋子都带有粪便细菌，其中一种主要的细菌为大肠杆菌——研究人员在96%的鞋底上发现了这种细菌。虽然许多类型的大肠杆菌对人类无害，但某些菌株可能导致严重的腹泻、尿路感染甚至脑膜炎。

"Not necessarily on every shoe, but on a good majority, you can find some type of E.coli there," Sexton said.

塞克斯顿说：“并不一定在每只鞋子上，但在绝大多数鞋子上你都能发现某种大肠杆菌。”

Apart from this ubiquitous germ, other studies have also found evidence of things like Staphylococcus aureus, which underlies¹⁰ a wide range of skin infections, and more worryingly, infections of the blood and the heart.

除了这种普遍存在的细菌，还有一些研究发现了鞋子上存在金黄色葡萄球菌的证据。这种细菌可能导致多种皮肤感染疾病，更让人担忧的是，还会感染血液和心脏。

Another prominent study published in 2014 in the journal Anaerobe sampled 30 households in Houston, Texas, for the presence of Clostridium difficile (C. difficile), a bacterium¹¹ with a long lifespan that commonly causes bowel¹² problems like diarrhea.

在另一项重要的研究中，研究人员采集了30种家用物品的样本，以检验梭状芽胞杆菌是否存在。梭状芽胞杆菌的存活期很长，通常会导致痢疾等肠道疾病。这项研究在德克萨斯州休斯顿开展，研究结果于2014年发表在《厌氧菌》期刊上。

Of all the household items they sampled, the researchers found that shoes harbored more C. difficile than even the surface of a toilet — underscoring the power that grubby soles could have to spread germs through a home.

在采集的所有家用品样本中，研究人员发现鞋子里的梭状芽胞杆菌比马桶表面的还要多，这也证实了脏鞋子在家里传播细菌的能力。

But despite the horrifying¹³ picture this paints of microbe-infested interiors, the research doesn't actually give us anything too serious to worry about. While many of us might want to launch into a house-cleaning frenzy¹⁴ at the thought of a wayward shoe, the reality is that the load of bacteria our shoes bring indoors isn't typically high enough to make the average healthy person very sick.

尽管这幅微生物入侵的画面很可怕，但这项研究实际上并没有给我们带来任何值得担心的严重问题。许多人也许一想到鞋上的细菌就想来一场大扫除，但事实是，我们的鞋子带进室内的细菌数量一般都不足以让普通的健康人生病。

"For a healthy individual, bacteria on shoes likely pose no or minimal¹⁵ risk," said Kevin Garey, the author on the 2014 study and professor at the University of Houston College of Pharmacy¹⁶. Usually, a healthy person would need to come into contact with thousands of microbes from one harmful bacterial strain to actually become infected with something, Sexton added.

美国休斯敦大学药学院教授凯文·加里说：“对于健康的人来说，鞋子上的细菌并不会构成风险，或者说风险很小。”凯文·加里也是前述2014年研究报告的作者。塞克斯顿说，健康的人通常需要接触很多有害细菌菌株才会真正感染。

Another point is that most of us don't spend a lot of time on the ground, where shoe bacteria dwell. "The exposure makes the poison. So if you're not exposed to it, you're not going to get sick from it," Sexton said. In some cases, layers of bacteria coating the floor can become "re-aerosolized" and enter the air we breathe, lifted by the draft from a window, for instance, Sexton explained. That might increase infection risk. But the greatest threat really lies on the ground. "I'd be more worried about a child crawling around on the floor. For a healthy adult, it's not too big of an issue," Sexton said.

另一点是，大多数人不会在地面上待很久，而地面正是鞋子携带细菌的主要聚集场所。塞克斯顿说：“接触才会导致感染。所以如果你没有接触，就不会因此生病。”他解释说，在某些情况下，地面上覆盖的一层细菌可能会因从窗外进来的一股气流而“重新雾化”，从而进入我们呼吸的空气。这可能增加感染风险。但最大的威胁实际上还是在地面上。他说：“我更担心的是在地板上爬来爬去的孩子。而对于健康的成年人来说，这不是太大的问题。”

Another group of people who may need to take extra precautions are those who are immunocompromised, meaning their defenses against infection are lower than usual. "In a person who is at risk for infections — usually someone recently hospitalized — attention to good household cleaning can be important," said Garey.

免疫功能不全的人们也需要格外防范，他们抵抗感染的能力比普通人要低。加里说：“对于可能被传染（一般最近住过院）的人来说，注意室内卫生很重要。”

In summary, if you're at risk of infection, or you have a small child, "it would be a good idea to take your outdoor shoes off when you enter your home," Garey told Live Science. "For most healthy persons, however, you can make the decision as much based on preference and habit, as potential health concern."总而言之，加里告诉趣味科学网站说，如果你有感染的风险，或者你有年幼的小孩，“那么你在进屋时最好把鞋子脱掉，不过对大多数健康人来说，你可以根据潜在的健康考量来做决定，也完全可以按照个人喜好和习惯”。

And it's worth remembering that bacteria exist elsewhere than on our shoes: They're in the air, on our skin, in our hair and inside our very guts¹⁸. In fact, we live in a constantly swirling¹⁹ bacterial soup that would be impossible to completely disinfect.

要记住，细菌不仅存在于鞋子上：它们还存在于空气中、我们的皮肤上、头发上、还有肠道里。实际上，我们一直与细菌共存，完全彻底的消毒是不可能的。

"Healthy bacteria in our gut¹⁷, skin and elsewhere keep us healthy and protect us from other bacteria that can cause us illness," Garey said. "I don't think everyone appreciates that some bacteria are also good for us."加里说：“我们的肠道和皮肤等处都有有益健康的细菌，使我们保持健康，免遭致病细菌的侵害。我并不认为所有人都知道有些细菌对我们是有好处的。”