Interpreting the Omicron drama

Omicron variant of SARS-CoV-2 emerged in southern Africa in November 2021, showing more mutations on the spike protein gene than other variants, high efficiency in transmission, immune evasion, causing a mild disease, mostly upper respiratory and low mortality. Its proximate parent is unknown. We argue that its evolutionary pathway was reverse zoonosis in rodents, acquiring rodent adaptation mutations and subsequently infecting humans as zoonosis – conceptually a ‘deviant’ with antigenic shift rather than variant with antigenic drift; its pathogenesis is modified by its cell entry pathway resulting in the absence of syncytia, low virus load, sparing lungs of pneumonia and hypoxia