U.S. health officials on Monday announced steps aimed at reducing the risk of Ebola in the United States amid international concerns over a new outbreak in the Democratic Republic of Congo, even as it told Americans the immediate risk was low.

CDC officials said they will screen and monitor travelers who have departed from, or were present in, the Democratic Republic of Congo, Uganda, and South Sudan during the past 21 days.

The measures will not apply to U.S. citizens, U.S. nationals, and lawful permanent residents, according to the CDC’s statement on its order, which is in effect for 30 days.

“The risk of Bundibugyo virus disease introduction into the United States is heightened by the virus’s incubation period, which can extend up to 21 days, allowing infected individuals to travel internationally while asymptomatic and therefore unlikely to be detected through routine symptom-based screening measures,” the CDC said.

U.S. officials will also ramp up contact tracing, laboratory testing capacity and hospital readiness nationwide, it added.

The CDC’s statement comes as medical personnel rushed to the frontlines of the outbreak in eastern DRC after the World Health Organization declared it a public health emergency over concern the disease could spread further after two cases were confirmed in neighboring Uganda.

(Reporting by Susan Heavey; editing by Katharine Jackson and Michelle Nichols)