COVID-19 infections in the U.S. continue to rise, with omicron BA.5 causing an estimated 82% of cases, according to the Centers for Disease Control and Prevention (CDC). It may be the most dominant strain, but it’s not the only one public health officials are monitoring. Omicron is a variant of COVID-19. BA.5 and BA.2.75 refer to as subvariants or strains of omicron. Variant basically means a mutation that occurs in the virus over time.