CORONAVIRUS

Variant first found in South Africa detected in the United States.

COLUMBIA, S.C. — A new variant of the coronavirus emerged Thursday in the United States, posing yet another public health challenge in a country already losing more than 3,000 people to COVID-19 every day.

The mutated version of the virus, first identified in South Africa, was found in two cases in South Carolina. Public health officials said it’s almost certain that there are more infections that have not been identified. They are also concerned that this version spreads more easily and that vaccines could be less effective against it.

The two cases were discovered in adults in different regions of the state and do not appear to be connected. Neither of the people infected has traveled recently, the South Carolina Department of Health and Environmental Control said Thursday.

“That’s frightening,” because it means there could be more undetected cases within the state, said Dr. Krutika Kuppalli, an infectious diseases physician at the Medical University of South Carolina in Charleston. “It’s probably more widespread.”

The arrival of the variant shows that “the fight against this deadly virus is far from over,” Dr. Brannon Traxler, South Carolina’s interim public health director, said in a statement. “While more COVID-19 vaccines are on the way, supplies are still limited. Every one of us must recommit to the fight by recognizing that we are all on the front lines now. We are all in this together.”

Viruses constantly mutate, and coronavirus variants are circulating around the globe, but scientists are primarily concerned with the emergence of three that researchers believe may spread more easily. Other variants first reported in the United Kingdom and Brazil were previously confirmed in the United States.

In South Carolina, the state health agency said the variant was found in one person from the state’s coastal region and another in its northeastern corner. The state gave little other information, citing privacy concerns, though Traxler said neither of the people was contagious any longer.

“Both were tested very early in the month, and my understanding is that both are doing well,” Traxler said.

Scientists last week reported preliminary signs that some of the recent mutations may modestly curb the effectiveness of two vaccines, although they stressed that the shots still protect against the disease. There are also signs that some of the new mutations may undermine tests for the virus and reduce the effectiveness of certain treatments.

The Centers for Disease Control and Prevention has reported at least 315 cases of the U.K.-discovered variant in the United States. Those reports have come from at least 28 states, and health officials believe it could become the dominant strain in the U.S. by March. That variant has been reported in at least 70 countries.

The first U.S. case of the variant found in Brazil was announced earlier this week by health officials in Minnesota. It was a person who recently traveled to that South American nation. That version of the virus has popped up in more than a half-dozen countries.

Biden on Monday reinstated COVID-19 travel restrictions on most non-U.S. travelers from Brazil, the U.K. and South Africa.