Illustration of a new gene (red) being inserted in the Covid-19 coronavirus particle's genome. The new coronavirus SARS-CoV-2 (previously 2019-CoV) emerged in Wuhan, China, in December 2019. The virus causes a mild respiratory illness (Covid-19) that can develop into pneumonia and be fatal in some cases. Some conspiracy theories suggest that the virus was created in a lab, possibly by genetically engineering an existing coronavirus.