Evolution and spread of SARS-CoV-2 likely to be affected by climate

COVID-19 pandemic has been a subject of extensive study. However, it is still unclear why it was restricted to higher latitudes during the initial days and later cascaded in the tropics. Here, we analyzed 176 SARS-CoV-2 genomes across different climate zones and Koppen's climate that provided insights about within-species virus evolution and its relation to abiotic factors. Two genetically variant groups, named G1 and G2, were identified, well defined by four mutations. The G1 group (ancestor) is mainly restricted to warm and moist, temperate climate (Koppen's C climate) while its descendent G2 group surpasses the climatic restrictions of G1, initially cascading into neighboring cold climate (D) of higher latitudes and later into the hot climate of the tropics (A). It appears that the gradation of temperate climate (Cfa-Cfb) to cold climate (Dfa-Dfb) drives the evolution of G1 into the G2 variant group, which later adapted to tropical climate (A) as well. It seems this virus followed an inverse latitudinal gradient in the beginning due to its preference towards temperate (C) and cold climate (D). Our work elucidates virus evolutionary studies combined with climatic studies can provide crucial information about the pathogenesis and natural spreading pathways in such outbreaks, which is hard to achieve through individual studies. Mutational insights gained may help design an efficacious vaccine.