Q&A: The novel coronavirus outbreak causing COVID-19

What is COVID-19, and what do we know so far about its clinical presentation? The virus responsible for COVID-19, SARS-CoV-2, is in the species SARS-like corona viruses. At 125 nm, it is slightly larger than influenza, SARS and MERS viruses. It is almost certainly a descendant from a bat corona virus of which there are many. The closest is a virus that originated from the Rhinolophus bat which is > 96% homologous with the current SARS-CoV-2 virus. It is only 79% homologous with the original SARS CoV [1]. The near identical gene sequences of 90 analysed cases from outside of China suggests it has likely emerged after a solitary species jump in early December 2019 from an unknown (likely mammalian) intermediate host [2]. Pangolins are an endangered ant-eating mammal from which scientists in Guangzhou have shown a coronavirus with 99% homology, with a receptor binding domain identical to that of SARS-CoV-2. However, this has not been confirmed, and, in addition, the pangolin's rarity means this may not be the only mammal involved.