The Trump administration on Friday said that it would block entry into the country for some legal permanent residents who had been in the Democratic Republic of Congo, Uganda or South Sudan, citing a limited ability to screen and monitor people who may have been exposed to Ebola.

The announcement by the Centers for Disease Control and Prevention was a response to a rapidly accelerating Ebola epidemic in the Democratic Republic of Congo, which is estimated to have sickened 750 people and killed 177. Health officials think that the deadly virus may have been spreading for weeks or even months. Two cases have been reported in neighboring Uganda.

Earlier this week, the Trump administration invoked a public health law, known as Title 42, to bar entry into the United States to immigrants who had been in Congo, Uganda or South Sudan over the previous 21 days. That order, which exempted U.S. citizens and legal permanent residents, is in effect for 30 days, but the administration could decide to extend it.

The policy announced on Friday would expand the ban, giving health officials the authority to bar legal permanent residents “who originate from or have recently traveled through” Congo, Uganda and South Sudan, according to an interim final rule posted in the Federal Register. The C.D.C. said the residents would be barred “for a limited period of time.”

South Sudan has not reported confirmed cases in the current outbreak, but it is considered at high risk because of its border with Congo and Uganda, and its limited health care infrastructure, according to the document.

The rule would still allow American citizens to return to the United States from those countries. But one American doctor who developed symptoms after treating a patient with Ebola was transported to Germany for medical care, as were his wife and their four children. Another physician who is thought to have been exposed was flown to the Czech Republic.