今天看到一篇来自剑桥大学Peter Forster的文章。这篇调查报告也在Proceedings of the National Academy of Sciences（PNAS）上有所登载https://www.pnas.org/content/early/2020/04/07/2004999117。
我是在剑桥自己的网站上看到对于这篇文章的介绍https://www.cam.ac.uk/research/news/covid-19-genetic-network-analysis-provides-snapshot-of-pandemic-origins。发表时间在PNAS刊登之后两天（4/9）。
文章的概要为
In a phylogenetic network analysis of 160 complete human severe acute respiratory syndrome coronavirus 2 (SARS-Cov-2) genomes, we find three central variants distinguished by amino acid changes, which we have named A, B, and C, with A being the ancestral type according to the bat outgroup coronavirus. The A and C types are found in significant proportions outside East Asia, that is, in Europeans and Americans. In contrast, the B type is the most common type in East Asia, and its ancestral genome appears not to have spread outside East Asia without first mutating into derived B types, pointing to founder effects or immunological or environmental resistance against this type outside Asia. The network faithfully traces routes of infections for documented coronavirus disease 2019 (COVID-19) cases, indicating that phylogenetic networks can likewise be successfully used to help trace undocumented COVID-19 infection sources, which can then be quarantined to prevent recurrent spread of the disease worldwide.
意思是说：作者在对160个完整的人类严重急性呼吸系统新冠病毒2（SARS-Cov-2）基因组进行的系统进化网络分析，我们发现了三个主要的变异体，它们的氨基酸变化不同，我们将其命名为A，B和C，其中A为与蝙蝠的型冠状病毒最为接近的。 A和C类型在东亚以外地区（即欧洲人和美国人中）的比例很高。相比之下，B型是东亚最常见的类型，而B型的祖先在没有变异成B型之前并没有在东亚以外传播，这表明在亚洲以外的地区对该类型具有影响力或免疫或环境抵抗力。该网络分析忠实地跟踪了已经记录在案的冠状病毒病2019（COVID-19）病例的感染途径，这表明系统发育网络同样可以成功地用于帮助跟踪未记录的COVID-19感染源，然后可以对其进行隔离以防止疾病的再次传播全世界。
这和原先听到日本和台湾的报告：一共有五种变异，中国有三种不同；但是和最早的病毒初始地点不在中国相吻合。我没有去找日本和台湾的报告的出处，因为我在这里更想翻译Peter Forster的文章。
原报告中并没有说明病毒的原始地点，也没有过多的介绍A类型。对于A型的介绍为：
There are two subclusters of A which are distinguished by the synonymous mutation T29095C. In the T-allele subcluster, four Chinese individuals (from the southern coastal Chinese province of Guangdong) carry the ancestral genome, while three Japanese and two American patients differ from it by a number of mutations.
患有A的两个子群病毒的患者中：有四个中国人（来自中国南方沿海省份广东省）带有祖传基因组，另外还有三名日本人和两名美国病人，他们的病毒都有许多突变。
It is noteworthy that nearly half (15/33) of the types in this subcluster, however, are found outside East Asia, mainly in the United States and Australia.
值得注意的是，该子集群中将近一半（15/33）类型来自于东亚以外地区，主要出现在美国和澳大利亚。
关于B型，报告提到：
For type B, all but 19 of the 93 type B genomes were sampled in Wuhan (n = 22), in other parts of eastern China (n = 31), and, sporadically, in adjacent Asian countries (n = 21). Outside of East Asia, 10 B-types were found in viral genomes from the United States and Canada, one in Mexico, four in France, two in Germany, and one each in Italy and Australia. Node B is derived from A by two mutations: the synonymous mutation T8782C and the nonsynonymous mutation C28144T changing a leucine to a serine. Cluster B is striking with regard to mutational branch lengths: While the ancestral B type is monopolized (26/26 genomes) by East Asians, every single (19/19) B-type genome outside of Asia has evolved mutations. This phenomenon does not appear to be due to the month-long time lag and concomitant mutation rate acting on the viral genome before it spread outside of China.
在对于93个B型病毒的基因采样中，有74个来自于亚洲：武汉22个，中国东部的其他地方31个，临近的其它亚洲国家31个。亚洲之外，美国和加拿大有10个B型病毒；墨西哥1个，法国4个，德国2个，意大利和澳大利亚各1个。B型是A型在经历了两次变异之后形成的。B型值得注意的地方是，虽然初始形态的B型都是在东亚地区，每一个在东亚以外的B型病毒，都是经过基因变异。这种现象感觉并不是因为在中国国内以月计算的时间之内传播，变异所造成的。
剑桥的文章中说到C型主要出现在欧洲：法国，意大利，瑞但，英国等地。中国大陆并没有有C型病毒的报告，但是新加坡，香港，韩国都有。意大利最早的被记录的病例来自于德国，但是也有可能跟新加坡的病毒群有关联。在发表在PNAS的文章里面，作者写道意大利的病毒源的时候，还提到了，墨西哥的病例传到了意大利，剑桥的文章里面并没有写。
The 'C' variant is the major European type, found in early patients from France, Italy, Sweden and England. It is absent from the study’s Chinese mainland sample, but seen in Singapore, Hong Kong and South Korea.
随着时间的推移，越来越多的科学研究和报告被发表出来了。到底病毒的来源在哪，我们就静观以待吧。
文章原稿 https://www.pnas.org/content/pnas/early/2020/04/07/2004999117.full.pdf