Molecular model of the SARS-CoV-2 coronavirus spike (S) protein (red) from the B.1.1.7 variant, showing its mutation sites. S proteins are found in the viral membrane, they bind to angiotensin converting enzyme 2 receptors (ACE2, blue) on host cell membranes and facilitate the virus's entry to the cell. The B.1.1.7 emerged in the UK, where, due to its increased transmissibility, it has become the predominant strain. SARS-CoV-2 emerged in Wuhan, China, in December 2019. The virus causes the disease Covid-19, a respiratory illness that can lead to pneumonia and can be fatal in some cases.