攜帶許多病毒的蝙蝠為什么不生病呢?

攜帶許多病毒的蝙蝠為什么不生病呢?

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

與非洲的埃博拉病毒和亞洲的尼帕病毒一樣，新的冠狀病毒——2019-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.

中國研究人員從武漢的患者身上提取了冠狀病毒樣本，武漢是中國中部首次發(fā)現(xiàn)疫情的城市。

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.

他們將新冠狀病毒2019-nCoV的基因序列與一個已知病毒文庫進行了比較，發(fā)現(xiàn)與中國西南部馬蹄蝠中發(fā)現(xiàn)的一種冠狀病毒有96%的匹配度。研究結果發(fā)表在本周的《自然》雜志上。

"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.

德克薩斯大學加爾維斯頓分校的病毒學家維尼特·梅納克里說：“就純遺傳學而言，它們太接近了，不能說它們沒有血緣關系，也不能說它們沒有共同的祖先。”他沒有參與這項研究。

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

梅納克里和許多其他研究人員認為，這種新的冠狀病毒從蝙蝠傳播到人類，可能會在另一種動物之間傳播。

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.

其他冠狀病毒也是如此。在2002年至2003年爆發(fā)的非典(SARS)疫情中，一種蝙蝠冠狀病毒感染了貓鼬家族的一員果子貍，并在市場上作為食物出售給人們。

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.

2012年首次發(fā)現(xiàn)的中東呼吸綜合征(MERS)疫情是由一種冠狀病毒引起的，這種病毒從蝙蝠傳播到駱駝，再傳播到可能飲用生駱駝奶或食用未煮熟的肉類的人身上。

So why do so many infectious diseases emerge from bats?

那么，為什么有那么多傳染病是從蝙蝠身上傳播出來的呢?

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，蝙蝠攜帶的病毒種類繁多，它們攜帶的病毒似乎更有可能傳染給人類。凱文·奧利瓦爾是美國非營利組織生態(tài)健康聯(lián)盟的研究副總裁，他說，科學家們還不完全確定原因，但這可能與一些蝙蝠傾向于攜帶的病毒家族有關。在蝙蝠身上發(fā)現(xiàn)了130多種不同的病毒。

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.

第二，蝙蝠和人類有很多接觸。除了南極洲之外，每個大陸上都生活著數十億只蝙蝠和1300多種不同的物種。“我們在蝙蝠體內發(fā)現(xiàn)了很多病毒，因為蝙蝠無處不在，”科羅拉多州立大學研究新出現(xiàn)傳染性病原體的麗貝卡·卡丁說。

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.

它們一起棲息在巨大而擁擠的群體中。不同蝙蝠物種的成員共享洞穴和被掏空的樹木，群體多達數百萬，在那里病毒可以通過密切接觸輕易地在它們之間傳播。

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.

與體型相比，它們的壽命更長，可以活30年以上。卡丁說:“因此，它們很長一段時間內會持續(xù)感染病毒，并將其釋放到環(huán)境中。”蝙蝠病毒通過尿液、糞便和唾液傳播。孟加拉國的尼帕病毒暴發(fā)與從被蝙蝠舔過或尿過的樹上采集的椰棗汁有關。

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

與此同時，你可能會想:為什么蝙蝠本身沒有受到病毒的影響?

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

事實證明，這個問題的答案與蝙蝠作為世界上唯一會飛的哺乳動物的地位有關。

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.

在飛行中，蝙蝠的體溫會飆升到超過100華氏度。它的心率可以達到每分鐘1000次以上。

"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.

“對大多數陸地哺乳動物來說，這些都是觸發(fā)死亡的信號，”在新加坡杜克大學-新加坡國立大學醫(yī)學院研究蝙蝠病毒的王林發(fā)說。但是蝙蝠每天都這樣。

Wang says it seems that bats have developed special immune systems to deal with the stress of flying.

王說，蝙蝠似乎已經發(fā)展出了特殊的免疫系統(tǒng)來應對飛行的壓力。

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).

它們的身體制造出其他哺乳動物沒有的分子，幫助修復細胞損傷。而且它們的系統(tǒng)不會對感染產生過度反應，這使它們不會因為攜帶的許多病毒而生病(也能預防糖尿病和癌癥等疾病)。

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.

王解釋說，這表明并不是病毒本身，而是身體對病毒的反應使我們生病。

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."

生態(tài)健康聯(lián)盟的奧利瓦爾說，讓我們明確一下：人們感染疾病不是蝙蝠的錯。“它們只是在某種程度上與這些病毒和細菌共同進化，基本上不會對它們造成任何傷害。”