Coronavirus particle, illustration. Different strains of coronavirus are responsible for diseases such as the common cold, gastroenteritis and SARS (severe acute respiratory syndrome). 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. The coronaviruses take their name from their crown (corona) of surface proteins, which are used to attach and penetrate their host cells. Once inside the cells, the particles use the cells' machinery to make more copies of the virus. This image is based on one that shows the ultrastructural morphology of the virus, and was created at the Centers for Disease Control and Prevention (CDC) in the USA.