Fans of the scaly anteater otherwise known as the pangolin can take heart in Nature‘s latest report, that might not have been the source of coronavirus after all. But then what was?:
Researchers at the South China Agricultural University in Guangzhou suggested pangolins as the animal source at a press conference on 7 February. Pangolins are highly sought-after in China for their meat and their scales; the latter are used in traditional medicine. Although sales of the animal are forbidden in China as part of a worldwide ban, they are still smuggled in from a handful of southeast Asian and African countries. The researchers said they had found a coronavirus in smuggled pangolins that was a 99% genetic match to the virus circulating in people.
But the result did not actually refer to the entire genome. In fact, it related to a specific site known as the receptor-binding domain (RBD), say the study’s authors, who posted their analysis1 on the biomedical preprint server bioRxiv on 20 February. The press-conference report was the result of an “embarrassing miscommunication between the bioinformatics group and the lab group of the study”, explains Xiao Lihua, a parasitologist at the South China Agricultural University and a co-author of the paper. A whole-genome comparison found that the pangolin and human viruses share 90.3% of their DNA.
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Two other papers published on 20 February, from groups in China, also studied coronaviruses from smuggled pangolins. The viruses were 90.23%3 and 91.02%4 similar, respectively, to the virus that causes COVID-19.
The genetic similarity should be higher than reported in these studies before the host can be identified, says Arinjay Banerjee, who studies coronaviruses at McMaster University in Hamilton, Canada. He notes that the SARS virus shared 99.8% of its genome with a civet coronavirus, which is why civets were considered the source. If pangolins are the origin of the current outbreak, says Banerjee, it is not the pangolins in these studies.
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Bats could have passed the virus to humans, but there are key differences between the RBD sites in the two viruses. This suggests that this specific bat coronavirus did not directly infect people, but could have been transmitted it to people through an intermediate host, say researchers.
The papers raise more questions than they answer, says Jiang Zhigang, an ecologist at the Chinese Academy of Sciences Institute of Zoology in Beijing.