为什么蝙蝠携带大量病毒却自己不生病？

小白老师说：据科学报道，蝙蝠不生病是因为蝙蝠的免疫系统是24小时工作的，从来不休息。另外，蝙蝠体温较高，飞行时体温可接近40度，可以有效抵抗病毒。反过来，由于病毒长期处于蝙蝠体内这样的恶劣环境中，也练就了病毒比较生猛的抵抗力。这也是为什么感染人之后人受不了的原因。高致病率，高死亡率。

点击这里播放音频：▼

注：以下文字和音频内容大体一致，但不是逐词对应的。英文来自NPR News，中文为小白老师翻译。

Like Ebola virus in Africa and the Nipah virus in Asia, the new coronavirus — 2019-nCoV — appears to have originated in bats.

与非洲的埃博拉病毒和亚洲的尼帕病毒一样，新型冠状病毒——2019年nCoV——似乎起源于蝙蝠。

Chinese researchers took samples of the coronavirus from patients in Wuhan, the city in central China where the outbreak was first detected.

中国研究人员从武汉患者身上采集到冠状病毒的样本，武汉是中国中部地区冠状病毒最先爆发的城市。

They compared the genetic sequence of the new coronavirus—2019-nCoV—to a library of known viruses and found a 96% match with a coronavirus found in horseshoe bats in southwest China. The findings were published in a study in Nature this week.

他们将新冠状病毒2019-nCoV的基因序列与已知病毒库进行了比较，发现96%与中国西南地区马蹄蝠中发现的冠状病毒相匹配。该发现发表在本周的《自然》杂志上。

“They’re too close in terms of their pure genetics to say they’re not related, or that they didn’t have a common ancestor,” says Vineet Menachery, a virologist at the University of Texas Medical Branch at Galveston who was not affiliated with the study.

德克萨斯大学加尔维斯顿分校的病毒学家 Vineet Menachery 说：“从纯粹的遗传学角度来说，两者太接近了，不能说它们没有亲缘关系，也不能说它们没有共同的祖先。”

Menachery and many other researchers think this new coronavirus spread from bats to humans, with a possible stop with another animal in between.

Menachery和其他许多研究人员认为，这种从蝙蝠传播到人类身上新型冠状病毒，中间可能还存在着另一种动物。

It’s happened with other coronaviruses. In the case of the SARS (Severe Acute Respiratory Syndrome) outbreak, from 2002-2003, a bat coronavirus jumped to civets, a member of the mongoose family, and was sold to people as food at markets. The MERS (Middle East Respiratory Syndrome) outbreak, first detected in 2012, was caused by a coronavirus that jumped from bats to camels to people who maybe drank raw camel milk or ate undercooked meat.

其他冠状病毒也有这种情况。在2002-2003年爆发的SARS，起因是一种蝙蝠冠状病毒传染给了猫鼬属的果子狸，果子狸又作为食物在市场上出售。于2012年首次发现的MERS（中东呼吸综合征）疫情，也是由冠状病毒引起的，这种病毒由蝙蝠传播给给骆驼，然后传染给了饮用生骆驼奶或食用未煮熟肉类的人。

First, bats carry a great variety of viruses — and the viruses they carry seem more likely to spread to people. Kevin Olival, vice president of research at EcoHealth Alliance, U.S.-based nonprofit, says scientists aren’t completely sure why, but it may have to do with the families of viruses that some bats tend to carry. There are over 130 different kinds of viruses found in bats.

首先，蝙蝠携带各种各样的病毒——它们携带的病毒似乎更容易传播给人类。美国非营利组织生态健康联盟研究副主席Kevin Olival说，科学家们还不能完全确定原因，但这可能与一些蝙蝠携带的病毒家族有关。蝙蝠体内有130多种不同的病毒。

Second, bats and humans have a lot of contact. There are billions of bats and more than 1,300 different species living on every continent except Antarctica. “There’s a lot of viruses we’re finding in bats because there’s a lot of bats out there,” says Rebekah Kading, who researches emerging infectious pathogens at Colorado State University.

其次，蝙蝠和人类有很多接触。除南极洲外，每个大陆上都生活着数十亿只蝙蝠和1300多种不同的物种。“我们在蝙蝠身上发现了很多病毒，因为那里有很多蝙蝠，” 科罗拉多州立大学研究新出现的传染病原体的Rebekah Kading说。

They roost in huge, crowded colonies together. Members of different bat species share caves and hollowed out trees in groups up to the millions, where viruses can pass easily between them through close contact with each other.

它们聚集在巨大拥挤的栖息地。不同蝙蝠种类的成员共享洞穴和被掏空的树木，成百上千万，病毒可以通过彼此的密切接触在蝙蝠之间轻易传播。

They have long lifespans relative to their size, and can live for more than 30 years. “So there’s a long time for them to be persistently infected with the virus and shed it into the environment,” Kading says. Bat viruses are shed through urine, feces and saliva. Outbreaks of Nipah virus in Bangladesh have been linked with date palm sap collected from trees that bats had licked or urinated on.

蝙蝠的寿命相对于它们的体型来说很长，可以活30年以上。“因此，他们很长一段时间内会持续感染病毒，并将其释放到环境中” ，卡丁说。蝙蝠病毒通过尿液、粪便和唾液传播。孟加拉国尼帕病毒的爆发与从蝙蝠舔过或尿过的树上采集的椰枣汁有关。

Meanwhile, you might be wondering: Why aren’t the bats themselves affected by the viruses?

讲到这里，你可能有这样的疑惑：为什么蝙蝠自己不受病毒的影响？

It turns out that the answer to that question has to do with the bat’s status as the world’s only flying mammal.

事实证明，这个问题的答案与蝙蝠是世界上唯一的飞行哺乳动物的地位有关。

During flight, a bat’s body temperature spikes to over 100 degrees Fahrenheit. Its heart rate can surge to more than 1,000 beats per minute. “For most land mammals, these are signals that would trigger death,” says Linfa Wang, who studies bat viruses at Duke-NUS Medical School in Singapore. But bats live it every day.

在飞行时，蝙蝠的体温会飙升至100华氏度以上。它的心率可以高达每分钟1000次以上。新加坡杜克国立医学院研究蝙蝠病毒的王林发说：“对大多数陆生哺乳动物来说，这些都是引发死亡的信号。” 但蝙蝠每天都活得好好的。

Wang says it seems that bats have developed special immune systems to deal with the stress of flying. Their bodies make molecules that other mammals don’t have, which help repair cell damage. And their systems don’t overreact to infections, which keeps them from falling ill from the many viruses they carry (and also prevents conditions like diabetes and cancer).

王林发说，蝙蝠似乎已经形成特殊的免疫系统来应对飞行的压力。它们的身体能制造其他哺乳动物没有的分子，这些分子能帮助修复细胞损伤。而且蝙蝠的免疫系统不会对感染反应过度，这能让它们不会因为携带众多而生病（还可以预防糖尿病和癌症等疾病）。

This shows that it’s not always the virus itself but the body’s response to the virus that can make us sick, explains Wang.

王林发解释说，这表明，让我们生病的不仅仅是病毒，有时是人体对病毒的反应让我们生病。

Olival at EcoHealth Alliance says let’s be clear: it’s not the bats’ fault that people are getting diseases. “They’ve just sort of coevolved with these viruses and these bugs that basically don’t cause them any harm.” The problem, he says, is when the viruses jump to new species. And it’s human activity that makes that likely to happen.

生态健康联盟的Olival说，必须澄清的是：“人类得病不是蝙蝠的错。” 它们只是在与这些病毒、以及这些基本上不会对它们造成任何伤害的疾病共同进化。” 他说，问题是病毒何时会传播给新物种。其实，正是人类自己的活动，让人类染上了病毒。

In wildlife markets, like the one in Wuhan, Olival says animals that would rarely mix in nature come together. A bat in a cage could be stacked over a civet. And those animals are then mixed with humans — for example, butchers handling animals without gloves.

Olival说，在野生动物市场上（比如武汉的野生动物市场），在自然界很少有交集的动物会被混在一起。笼子里的蝙蝠可以堆在果子狸上。然后这些动物又与人类混合——比如屠夫在不戴手套宰杀动物。

“The way that we’re coming into contact with these animals, hunting, selling, and trading them is to a scale that really we haven’t seen before,” he says.

他说：“我们与这些动物接触、捕猎、出售和交易的方式，达到了我们闻所未闻的规模。”。

Investigators found traces of the virus in 22 stalls and a garbage truck at the Huanan Seafood Market in Wuhan, which also sold live animals. The market was shut down in early January, as it was tied to many of the early cases.

调查人员在武汉华南海鲜市场的22个摊位和一辆垃圾车中发现了病毒的痕迹，该市场还出售活体动物。市场在一月初被关闭，因为它与许多早期病例有关。

While the animal in the middle is still a mystery (some early reports point to pangolin), Wang says it’s easy to imagine how an infected animal could spread the virus to humans. “The animal can sneeze, the animal can urinate,” he says, “If a human touches [it] and blows their nose or whatever — they’ve got it.” Infection could also spread through eating undercooked meat.

虽然中间的动物仍然是一个谜（一些早期报告认为是穿山甲），但王林发说，很容易想象被感染的动物如何将病毒传播给人类。” “动物会打喷嚏，动物会小便”，他说，“如果有人碰了它，擤了擤鼻子什么的——他们就染上病毒了。” 感染也可能通过吃未煮熟的肉传播。

And bat researchers stress that bats aren’t just a possible source of viruses. They play a hugely important role in Earth’s ecosystem. They eat tons of insects and pollinate plants and disperse seeds for hundreds of plant species. And they’ve found a way to coexist with the viruses they carry — which means, says Wang, that even though bats may be the source of viruses that affect humans, they could also be the source of potential therapies if we study their immune systems.

蝙蝠研究人员强调蝙蝠不仅仅是病毒的可能来源。它们在地球生态系统中扮演着极其重要的角色。它们以昆虫为食，为植物授粉，并为数百种植物散布种子。它们找到了与自身携带的病毒共存办法，这意味着，既然蝙蝠可能是影响人类的病毒来源，那么如果我们研究其免疫系统，它们也可能成为潜在疗法的来源。