Coloured transmission electron micrograph (TEM) of a cell infected with SARS-CoV-2 coronavirus particles (red). SARS-CoV-2 (previously 2019-nCoV) was first identified in Wuhan, China, in December 2019, and has been declared a pandemic. It is an enveloped RNA (ribonucleic acid) virus. It causes Covid-19, a respiratory infection that can lead to fatal pneumonia. Social restrictions and infection control measures have been put in place to slow the spread of the virus.