E-Mail Research from the University of Kent, Goethe-University in Frankfurt am Main, and the Philipps-University in Marburg has provided crucial insights into the biological composition of SARS-CoV-2, the cause of COVID-19, revealing vital clues for the discovery of antiviral drugs. Researchers compared SARS-CoV-2 and the closely related virus SARS-CoV, the cause of the 2002/03 SARS outbreak. Despite being 80% biologically identical, the viruses differ in crucial properties. SARS-CoV-2 is more contagious and less deadly, with a fatality rate of 2% compared to SARS-CoV's 10%. Moreover, SARS-CoV-2 can be spread by asymptomatic individuals, whereas SARS-CoV was only transmitted by those who were already ill. Most functions in cells are carried out by proteins; large molecules made up of amino acids. The amino acid sequence determines the function of a protein. Viruses encode proteins that reprogramme infected cells to produce more viruses. Despite the proteins of SARS-CoV-2 and SARS-CoV having largely the same amino acid sequences, the study identifies a small subset of amino acid sequence positions that differ between them and are responsible for the observed changes in the behaviour of both viruses.