据2019年10月下旬的一则报道，在中国武汉出现不明病毒导致的肺炎患者，随后确定了一种新型冠状病毒为致病病原体并临时命名为2019新冠状病毒（2019-nCoV）。截至到2020年2月3日16点40分，全国确诊病例已经达到17267例，成为了一场真正席卷全国的传染病。

2019-nCoV是一种新型的冠状病毒，并且是很容易发生变异的RNA单链病毒。冠状病毒已在数种禽类及哺乳动物中被发现，包括骆驼、蝙蝠、果子狸、老鼠、狗和猫等。而新型的哺乳动物冠状病毒也被陆续鉴定出。例如，2018年蝙蝠起源的HKU2相关冠状病毒导致了猪的致命性急性腹泻综合征。

那么这次如此大范围传播的新型冠状病毒到底有哪些特征呢？对此，一项最新的研究就9例确诊患者肺泡细胞中提取出的2019-nCoV，通过基因组学的分析寻找到病毒的起源以及如何与人体内细胞结合的途径。

从这9例患者的样本分析得到了8个完整的两个部分的2019-nCoV基因组序列，这些数据已保存在中国国家微生物数据中心（登录号NMDC10013002和基因组登录号NMDC6001300

2-01至NMDC60013002-10），而BGI的数据已保存在中国国家基因库（登录号CNA0007332–35）。

基于这些基因组分析，在所有样品中鉴定出的一些重叠群均与蝙蝠SARS乙型冠状病毒bat-SL- CoVZC45密切相关，8个完整的基因组在整个基因组中几乎是相同的，这表明2019-nCoV有极大的可能是来源于蝙蝠。

并且从结果来看，人身上的新型冠状病毒和这组基因数据很相似，表明2019-nCoV很可能是最近才发生了变异从而可以在人身上进行传播，这进一步落实了之间的推测。

对2019-nCoV和蝙蝠中的基因组进行测序对比（图片来源：参考文献1）

对2019-nCoV完整基因组进行的Blastn搜索显示，GenBank上最紧密相关的病毒是bat-SL-CoVZC45（序列同一性87.99％；查询覆盖率99％）和另一种蝙蝠起源的SARS样乙型冠状病毒， bat-SL-CoVZXC21（登录号MG772934；序列同一性87.23％；查询覆盖率98％）。在五个基因区域（E，M，7，N和14）中，序列同一性大于90％，在E基因中最高（98·7％）。2019-nCoV的S基因与bat-SL-CoVZC45和bat-SL-CoVZXC21表现出最低的序列同一性，仅占75％左右。此外，1b中的序列同一性（约86％）低于1a中的序列同一性（约90％）。大多数编码蛋白在2019-nCoV和相关的蝙蝠衍生冠状病毒之间显示出高度的序列同一性。

冠状病毒需要感染人体，那么就需要和人体的细胞相结合——结合细胞上的受体。包膜棘突蛋白（S）介导受体结合和膜融合，对于确定宿主的选向性和传递能力至关重要。

进一步的分析表明，与其它乙型冠状病毒一样，受体结合域由核心和外部亚域组成。值得注意的是，2019-nCoV受体结合结构域的外部子结构域与SARS-CoV的结构域更相似。该结果表明，2019-nCoV也可能使用血管紧张素转化酶2（ACE2）作为细胞受体。而ACE2 广泛存在于人的肺毛细血管内皮细胞上，这也是为什么此次新冠病毒会造成严重的肺炎的原因。

目前基本上可以确定2019-nCoV是来自于蝙蝠，而可以结合的细胞种类也和我们之前猜想的类似。但是作为一种典型的单链RNA病毒，其可怕的变异性才最值得我们警惕——几乎每个周期都可能会发生变异，这就意味着随着传播人数的增多，其变异性可能会大大增加。

不论是传染性的升高和致死率的提高，都不是我们希望看到的结果。而我们需要更加审慎的一点是：在野生动物上隐藏的病毒库，可能在不经意间传播到人类这个群体中来，病毒的变异性很可能会给人类群体引发严重的后果。

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