COVID-19 variants have helped the disease continue to spread because they carry mutations that can strengthen the virus’s ability to infect individuals. Infection can occur even in people who were vaccinated or who previously had COVID-19. Variants may also cause more severe disease or potentially escape certain treatments. Omicron, first detected in Botswana in November 2021, quickly became the primary strain circulating globally. Its sublineages included highly infectious BA.4 and BA.5 and BA.2, which gave rise to the highly transmissible XBB.1.5 variant.
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