Graphical representation of the genome of the first fully sequenced isolate of the virus SARS-CoV-2, the cause of Covid-19. The SARS-CoV-2 genome consists of RNA (ribonucleic acid). The length of the path seen here is proportional to the size of the genome. It is colour-coded according to the percentage of the nucleotide bases guanine (G) and cytosine (C) present, with 20% as red, through orange (30%), yellow, green (40%) and blue to purple (50%). The curvature of the path is proportional to the number of repeats in the genome and the curvature direction is determined by whether the GC content is higher or lower than average. SARS-CoV-2 emerged in Wuhan, China, in December 2019 and spread worldwide infecting tens of millions of people and causing over one million deaths.