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Coloured transmission electron micrograph (TEM) of SARS-CoV-2 coronavirus particles isolated from a US case of the disease Covid-19. SARS-CoV-2 (previously 2019-nCoV) was first identified in Wuhan, China, in December 2019. It is an enveloped RNA (ribonucleic acid, dark) virus. The coronaviruses take their name from their crown (corona) of surface proteins, which are used to attach and penetrate their host cells. Covid-19 is a respiratory infection that can lead to fatal pneumonia. As of the 18th February 2020, over 70,000 have been infected in China with over 1,700 deaths. There have been over 750 confirmed cases outside of China, with three deaths. In China travel restrictions and infection control measures have been put in place to slow the spread of the virus. (KEYSTONE/SCIENCE PHOTO LIBRARY/NATIONAL INSTITUTES OF HEALTH-RML/SCIENCE PHOTO LIBRARY)