As the globally prominent BA.5 variant of the coronavirus continues to drive a surge in Covid-19 cases in many countries, a new sub-lineage known as BA.2.75 is also on the rise, particularly in India. Although health experts are not yet sure if the mutation can cause severe illness, its ability to spread rapidly and to make people sick even when they have been vaccinated or had previous infections. The experts say the strain underscores a continued need for booster shots and mask wearing to…