據(jù)2019年10月下旬的一則報道，在中國武漢出現(xiàn)不明病毒導(dǎo)致的肺炎患者，隨后確定了一種新型冠狀病毒為致病病原體并臨時命名為2019新冠狀病毒（2019-nCoV）。截至到2020年2月3日16點40分，全國確診病例已經(jīng)達到17267例，成為了一場真正席卷全國的傳染病。

2019-nCoV是一種新型的冠狀病毒，并且是很容易發(fā)生變異的RNA單鏈病毒。冠狀病毒已在數(shù)種禽類及哺乳動物中被發(fā)現(xiàn)，包括駱駝、蝙蝠、果子貍、老鼠、狗和貓等。而新型的哺乳動物冠狀病毒也被陸續(xù)鑒定出。例如，2018年蝙蝠起源的HKU2相關(guān)冠狀病毒導(dǎo)致了豬的致命性急性腹瀉綜合征。

那么這次如此大范圍傳播的新型冠狀病毒到底有哪些特征呢？對此，一項最新的研究就9例確診患者肺泡細胞中提取出的2019-nCoV，通過基因組學的分析尋找到病毒的起源以及如何與人體內(nèi)細胞結(jié)合的途徑。

從這9例患者的樣本分析得到了8個完整的兩個部分的2019-nCoV基因組序列，這些數(shù)據(jù)已保存在中國國家微生物數(shù)據(jù)中心（登錄號NMDC10013002和基因組登錄號NMDC6001300

2-01至NMDC60013002-10），而BGI的數(shù)據(jù)已保存在中國國家基因庫（登錄號CNA0007332–35）。

基于這些基因組分析，在所有樣品中鑒定出的一些重疊群均與蝙蝠SARS乙型冠狀病毒bat-SL- CoVZC45密切相關(guān)，8個完整的基因組在整個基因組中幾乎是相同的，這表明2019-nCoV有極大的可能是來源于蝙蝠。

并且從結(jié)果來看，人身上的新型冠狀病毒和這組基因數(shù)據(jù)很相似，表明2019-nCoV很可能是最近才發(fā)生了變異從而可以在人身上進行傳播，這進一步落實了之間的推測。

對2019-nCoV和蝙蝠中的基因組進行測序?qū)Ρ龋▓D片來源：參考文獻1）

對2019-nCoV完整基因組進行的Blastn搜索顯示，GenBank上最緊密相關(guān)的病毒是bat-SL-CoVZC45（序列同一性87.99％；查詢覆蓋率99％）和另一種蝙蝠起源的SARS樣乙型冠狀病毒， bat-SL-CoVZXC21（登錄號MG772934；序列同一性87.23％；查詢覆蓋率98％）。在五個基因區(qū)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基因與bat-SL-CoVZC45和bat-SL-CoVZXC21表現(xiàn)出最低的序列同一性，僅占75％左右。此外，1b中的序列同一性（約86％）低于1a中的序列同一性（約90％）。大多數(shù)編碼蛋白在2019-nCoV和相關(guān)的蝙蝠衍生冠狀病毒之間顯示出高度的序列同一性。

冠狀病毒需要感染人體，那么就需要和人體的細胞相結(jié)合——結(jié)合細胞上的受體。包膜棘突蛋白（S）介導(dǎo)受體結(jié)合和膜融合，對于確定宿主的選向性和傳遞能力至關(guān)重要。

進一步的分析表明，與其它乙型冠狀病毒一樣，受體結(jié)合域由核心和外部亞域組成。值得注意的是，2019-nCoV受體結(jié)合結(jié)構(gòu)域的外部子結(jié)構(gòu)域與SARS-CoV的結(jié)構(gòu)域更相似。該結(jié)果表明，2019-nCoV也可能使用血管緊張素轉(zhuǎn)化酶2（ACE2）作為細胞受體。而ACE2 廣泛存在于人的肺毛細血管內(nèi)皮細胞上，這也是為什么此次新冠病毒會造成嚴重的肺炎的原因。

目前基本上可以確定2019-nCoV是來自于蝙蝠，而可以結(jié)合的細胞種類也和我們之前猜想的類似。但是作為一種典型的單鏈RNA病毒，其可怕的變異性才最值得我們警惕——幾乎每個周期都可能會發(fā)生變異，這就意味著隨著傳播人數(shù)的增多，其變異性可能會大大增加。

不論是傳染性的升高和致死率的提高，都不是我們希望看到的結(jié)果。而我們需要更加審慎的一點是：在野生動物上隱藏的病毒庫，可能在不經(jīng)意間傳播到人類這個群體中來，病毒的變異性很可能會給人類群體引發(fā)嚴重的后果。

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