Molecular models of potential targets for drugs to treat infection with the SARS-CoV-2 coronavirus. From left to right they are; spike (S) protein, RNA-dependent RNA (ribonucleic acid) polymerase (RdRp) and main protease (Mpro). S proteins are found in the viral membrane, they bind to receptors on host cell membranes and facilitate the virus's entry in to the cell. RdRp catalyses the replication of RNA (the viral genome) from an RNA template. Mpro processes two long polyproteins that the virus needs to replicate new viruses. SARS-CoV-2s emerged in Wuhan, China, in December 2019, and causes a mild respiratory illness (Covid-19) that can develop into pneumonia and be fatal in some cases.