(WASHINGTON, D.C.) — With health officials keeping an eye on the rise in COVID-19 mutations, particularly the more transmissible U.K. and South African variant — the latter was found in two people in South Carolina on Thursday.

The two cases, reported in adults who live in two separate counties, has raised concern if the variant has already taken hold.

The state’s Department of Health and Environmental Control reports, “There is no known travel history and no connection between these two cases.”

The Centers for Disease Control and Prevention has consistently urged Americans to “avoid travel at this time,” especially to countries that have been affected with the new coronavirus variants.

The B.1.351 South African variant has already been located in 30 other countries, according to health officials.  The variant is not considered more deadly but is is more transmissible.

“Experts agree that existing vaccines work to protect us from this variant, even if we don’t know precisely how effective they are,” South Carolina officials said. “At this time, there’s no evidence to suggest that the B.1.351 variant causes more severe illness.”

 Dr. Anthony Fauci reacted to the news on Good Morning America on Thursday and said the South African variant in particular “troubles” him.

Saying vaccines are “diminished by multifold” when tested against the South African variant, Fauci added, “It’s still within the range of what you would predict to be protective… but I take no great comfort in that.”

Fauci says scientists are already hard at work developing a booster shot that will specifically target the South African variant.

COVID-19 has infected over 25.7 million Americans and killed over 433,000 people, reports Johns Hopkins University.