President Joe Biden on Monday will formally reinstate coronavirus disease 2019 (Covid-19) travel restrictions on non-US travelers from Brazil, Ireland, the United Kingdom and 26 other European countries that allow travel across open borders, according to two White House officials.

The officials, who spoke on the condition of anonymity to discuss the order, also confirmed Sunday that South Africa would be added to the restricted list because of concerns about a variant of the virus that has spread beyond that nation.

Biden is reversing an order from President Donald Trump in his final days in office that called for the relaxation of the travel restrictions as of Tuesday.

The decision to reverse the order is not surprising, but the addition of South Africa to the restricted travel list highlights the new administration’s concern about mutations in the virus.

The South Africa variant has not been discovered in the United States, but another variant — originating in the United Kingdom — has been detected in several states.

Reuters was first to report Biden’s decision to add South Africa to the list.

Biden last week issued an executive order directing federal agencies to require international air travelers to quarantine upon US arrival. The order also requires that all US-bound passengers ages 2 and above get negative Covid-19 test results within three days before traveling.