A mutated strain of the coronavirus first found in South Africa has been detected for the first time in the United States, reported the Associated Press Thursday.

Two cases were found in South Carolina Thursday, and public health officials are certain there are more coming that simply have not been identified yet. They are also concerned that this version spreads more easily and that vaccines could be less effective against it.

The two cases were found in two adults from different regions of the state who have no connection to one another. Neither of them have traveled recently.