Illustration of the structure of a coronavirus spike (S) protein. S proteins are found in the viral membrane, they bind to receptors on host cell membranes and facilitate the virus's entry to the cell. Once inside the cell, the virus uses the cells' machinery to make more copies of itself. Different strains of coronavirus are responsible for diseases such as the common cold, gastroenteritis and SARS (severe acute respiratory syndrome). A new coronavirus (2019-CoV) emerged in Wuhan, China, in December 2019. The virus causes pneumonia and can be fatal in some cases.