Health officials in South Carolina confirmed that two people in the state have tested positive for a new coronavirus variant that was first identified in South Africa. These are the first two confirmed cases of the more infectious variant in the U.S. The South African strain, which is called B.1.351, is one of several new variants wthat have emerged around the world and are raising concern among government officials and medical experts over their transmissibility. The South Carolina Department of Health and Environmental Control confirmed the two cases in residents of the Lowcountry and the Pee Dee region in a news release on Thursday. Neither adult has a travel history, and they do not know each other, officials said. Health departments use genomic sequencing to identify new strains or variants among COVID-19 test samples; this is how the South Carolina health department identified both cases. Another variant, the B.1.1.7, which was first detected in the United Kingdom, has infected more than 300 people in the U.S. so far, according to the latest figures from the Centers for Disease Control and Prevention. This variant is also thought to be more infectious. This week, Moderna Inc. MRNA, +5.73% said a laboratory study demonstrated that its COVID-19 vaccine is less effective against the B.1.351 strain, and Regeneron Pharmaceuticals Inc. REGN, -0.49% said one of the two antibodies used in its COVID-19 treatment is also less effective against this strain of the virus.