Coronavirus host cell receptor with antibody, illustration. Molecular model of the angiotensin II type 2 receptor (ribbons) in a host cell membrane binding to an antibody (molecular model). This type of receptor is the entry point for the Covid-19 coronavirus. Antibodies are part of the immune system and help to fight disease. Covid-19, which emerged in Wuhan, China, in December 2019, is a mild respiratory illness that can develop into pneumonia and be fatal in some cases. It is caused by the SARS-CoV-2 (previously 2019-nCoV) coronavirus. As of March 2020, the virus has spread to many countries worldwide and has been declared a pandemic. Over 100,000 have been infected with several thousand deaths.