The Delta variant is a strain of the SARS-CoV-2 virus, which causes COVID-19. First identified in India in late 2020, it quickly became a dominant variant in many countries due to its increased transmissibility. This means it spreads more easily from person to person compared to earlier strains. In addition to being more contagious, the Delta variant may lead to more severe illness in some individuals. Vaccines remain effective against it, particularly in preventing severe disease and hospitalization. Public health measures, such as wearing masks and practicing social distancing, continue to be important in controlling its spread.