3.5. Animal Reservoirs
In 2010, Shi et al. isolated a SARS-like coronavirus which was highly homologous to the SARS-CoV, confirming that Rhinolophus sinicus (Chinese rufous horseshoe bat) was a natural host of the SARS-CoV [46]. Bats are known to be hosts for 30 coronaviruses based on complete genomic sequences analysis [47]. Epidemiological investigations have shown that civet cats in the wildlife market were the direct source of SARS-CoV [48]. Among the four patients with SARS discovered during the winter of 2003-2004, two were waitresses at a restaurant in Guangzhou, China, and one was a customer who ate in the restaurant a short distance from a civet cage. All six civets in this cage were tested positive for SARS-CoV [48].
The new emerging SARS-CoV-2 shares about 80% of the gene sequence of SARS-CoV, released by the Military Medical Research Institute of Nanjing Military Region in 2003 [28]. Recently, Shi et al. reported that the sequence similarity of coronavirus between SARS-CoV-2 and the coronavirus isolated from Rhinolophus affinis is 96.2%, and suggested that bats may be the source of the virus [49]. So far, the intermediate hosts of SARS-CoV-2 are elusive and have been reported to be snakes, minks, or variable others [50,51]. Recently, a research group of South China Agricultural University reported that pangolins may be one of the intermediate hosts for SARS-CoV-2, by analyzing more than 1,000 metagenomic samples, because they found that 70% of pangolins are positive for the coronavirus. Moreover, the virus isolate from pangolin shared 99% sequence similarity with the current infected human strain SARS-CoV-2 [52]. Taking this recent research into consideration, we agreed that pangolin is more likely to be one of intermediate hosts of SARS-CoV-2.