https://mp.weixin.qq.com/s/muHHsE1BESbQiPNfFEqpWg
At the beginning of 2020, people's knowledge of infectious diseases has risen to a new height. This time count Wuhan novel coronavirus pneumonia, in our mind, in recent decades the world has experienced many dangerous infectious disease outbreaks.
In fact, much more than the memory of the Chinese people, "SARS", in 1994, the Australian Hendra virus outbreak, three years after the outbreak of the virus high Menan, 1998, the Nipah virus outbreak in Malaysia and Tioman (Malaysia islands) virus .
Then later we are more familiar with SARS, MERS, and the comeback of Ebola virus and Marburg virus, as well as Hantavirus, Lassa virus, rabies virus, and so forth.
These viruses are spread by animal hosts to humans, as they say on the general medical emerging viruses or new viruses. Strangest of all (note the all) of the above-mentioned virus associated with bats. Bat what is special ability to attract so many terrible virus of all ages?
01
We start with the people most familiar with "SARS" Speaking of, it can be considered the most immediate memories of the occasion.
About SARS virus traced the source, then the mainstream view is that the source of the virus is on the civets' game market " . In critical situations, come only in the preliminary speculation and lack of evidence, the relevant departments of the sale of civet cats on the market on a large scale culling.
However, the identity of the "murderers" of civet cats has been unable to take real, although similar to a virus similar to isolate the SARS virus from their body, but further study found that the incidence of the virus in civet cats who do not, even artificial infections We can not succeed, but can not find evidence that civets infect humans.
Bats have been back for the pot of civet cats
There are indications that the civet cat may not be the real source of the virus. So after "SARS" calm years, epidemiologists have also been no drop this pending case.
2013, University of Hong Kong, Professor Yuen Kwok-yung pointed out, SARS virus in civet cats are not the natural host is more likely to be "Chinese horseshoe bat" bat called. However, as the coming of "suspects", the source said the bat is also facing difficulties then insufficient evidence of civet cats, the study found the presence of the SARS virus to infect humans critical difference separated from the body of the Chinese horseshoe bat coronavirus, people can not use and civet cats receptors, which means that the virus is limited to internal communication bat.
University of Hong Kong, Professor Yuen Kwok-yung
Despite evidence to "conviction" is not found, but this hypothesis given scientists detected the correct direction. In order to solve the awful "outstanding issues", Wuhan Institute of Virology Danzheng Li and Cui Jie, a large number of horseshoe bat around the country sampling. They bats living in the cave for as long as five years of monitoring, collecting fresh bat droppings and anal swab samples. Finally found a coronavirus similar to the human version of the virus strains in a cave in Yunnan Province.
They genomic sequence analysis of 15 strains from these bats and found that they all contain common components constituting the genome of the human version of the virus. Although no single bat contain exactly the same with the human SARS coronavirus strains, but these strains showed that frequent restructuring. This finding confirms the basic Professor Yuen Kwok-yung guess the origin of the bat.
Chinese rufous horseshoe bat
Wuhan recent outbreak of novel coronavirus as having high similarity to the SARS virus, so now the scientific community is also suspected of Wuhan bats are the natural hosts of coronaviruses, but further studies are needed to determine the good.
02
Indeed bat in the food chain of the virus in the extraordinary position, is known as the "nature of live virus", SARS only one of many living In one bats only.
In 1994, a racecourse town of Hendra outbreak of a disease in Australia, killing 14 horses and one person. Leading to the outbreak of the virus is called Hendra virus, from bats are suspected. In the course of the investigation, researchers found that the presence of Hendra virus antibodies central flying foxes, Gray-headed flying fox, red fox small bat, flying fox four kinds of glasses flying foxes vivo. Since then, isolated Hendra virus in a pregnant gray-headed flying foxes reproductive tract.
虽然没有发现这种病毒从狐蝠直接传播给马，但在实验室的感染研究表明，可能是马取食的牧草被携带病毒的狐蝠胎儿组织或胎水污染导致病毒传播。另一种可能的途径是马采食狐蝠吃剩的果实而被感染，病毒在马群中通过尿液和鼻腔分泌物传播，人则是通过接触病马感染。
亨德拉病毒相关信息
亨德拉病毒的“近亲”尼帕病毒是世界上最危险的病毒之一，被列为生物安全 4 级病原。尼帕病毒最初在 1998 年到 1999 年间暴发于马来西亚和新加坡，感染猪群和猪农，276 人被感染，其中 105 人死亡。
由于尼帕病毒与亨德拉的亲缘关系，蝙蝠成为第一个怀疑目标。马来西亚蝙蝠种类很多，有 13 种食果蝙蝠和 60 多种食虫蝙蝠，研究证实，有 4 种食果蝙蝠和 1 种食虫蝙蝠体内有尼帕病毒的抗体。2004 年孟加拉国中部也暴发了尼帕疫情，感染者病死率高达 75%，“凶手”也是蝙蝠。
狐蝠
除此之外，包括埃博拉病毒、马尔堡病毒这些令人闻风丧胆的杀手级病毒的自然宿主也都是蝙蝠。
这两种病毒同属于丝状病毒科，都能引起非常烈性的人类疾病。自 1976 年埃博拉病毒首次爆发以来，它的致死率高达惊人的 83%，当然这当中也有对其认识不足和医疗水平不足的因素，但不可否认的是埃博拉的确是最致命的一种传染病，同属的马尔堡病毒也同样非常烈性。
1995 年，扎伊尔地区暴发埃博拉感染疫情，造成 315 人感染，254 人死亡。研究人员随即对采于该地区的 3066 份脊椎动物样本进行了病毒检测和病毒分离，所有结果均是阴性。
埃博拉病毒伪彩色电镜照片，很容易知道它为什么属于丝状病毒属
研究人员用病毒感染了 24 种植物和 19 种脊椎动物和无脊椎动物，发现只有蝙蝠支持埃博拉病毒的复制，但没有表现出明显症状，因此研究推测蝙蝠可能是埃博拉病毒的自然宿主。
国际病毒分类委员会列出有 25 个科的病毒能够感染脊椎动物，其中有 10 个科的病毒与蝙蝠有关。这 10 个科的病毒种又有 9 个科是属于 RNA 病毒科。为什么是蝙蝠？为什么是 RNA 病毒？
03
最浅显的道理很容易得出，蝙蝠数量巨大种类繁多，在全世界约有 1107 种，据估计全部哺乳类当中有近五分之一，是仅次于啮齿目的第二大类群。
而且蝙蝠还是除人类之外分布范围最广的哺乳类动物类群，除了南北极全世界都能找到蝙蝠的踪迹，甚至包括沙漠。这就意味着蝙蝠与更广泛分布的人类接触的概率相当大。另外，蝙蝠群居的习性给病毒的传播提供了完美的环境，超高密度的亲密群居让病毒能够快速地传播。
飞行则是另外一个重要的因素，在游戏《瘟疫公司》当中，鸟类传播是传染病的重要传播手段，而蝙蝠同样也会像候鸟一样随季节变化而迁徙，极大地增加了病毒传播的范围。
但飞行的秘密还不仅仅在于活动范围这一点。为了适应飞行的生存方式，蝙蝠的代谢率比起同体型的哺乳动物甚至要更高，这也意味着更容易产生遗传物质的损伤，因此在漫长的进化征途中，蝙蝠发展出了超强的 DNA 损伤修复能力。
他们几乎不会患癌症，并且寿命比同体型的哺乳动物长很多，寿命最长的小棕蝠能存活超过 35 年，绝大多数的品种寿命也都在 10 年以上，相比之下，同等体型的啮齿类大约只有 2 年的寿命。
超强的 DNA 修复能力让蝙蝠的免疫系统变得十分神奇，修复基因在完成本职工作之外还能显著抑制病毒的复制。
另外蝙蝠细胞耐热性很高，在 40℃的体温下仍然能保持相当稳定的状态，这也一定程度地抑制了病毒的复制，当然百万年的共同生活让一些病毒已经适应了高体温，这意味着在感染人类后，我们身体常规的发热机制可能无法对病毒的复制造成有效的干扰。
更重要的一点是，在蝙蝠体内长治久安的这些 RNA 病毒拥有非常高的遗传多样性，RNA 基因组大小很大，并且具有很高的重组率，有很大机率突然获得感染蝙蝠外其他哺乳动物的能力。因此来自蝙蝠的这些新兴病毒来势汹涌，防不胜防，往往都会造成重大突发公共卫生安全事件。
数百万年来这些病毒也将蝙蝠当作一个温馨的港湾，在它们的体内成长进化，直到有朝一日某个能走出家门的子孙诞生。目前我们能做的就是继续研究蝙蝠组学，以及加强民众对突发公共卫生安全事件的应对防范意识，虽然我们可能无法阻止下一种未知病毒的到来，但我们一定希望下一次的损失更小。