The United States (US) has temporarily expanded its Ebola-related travel restrictions to include lawful permanent residents, commonly known as green card holders, who recently travelled to three African countries affected by the outbreak.

According to a Reuters report, the new measure applies to people who have been in the Democratic Republic of the Congo, Uganda or South Sudan within the previous 21 days.

The restriction was announced by the Centers for Disease Control and Prevention, which said the decision was aimed at preventing the virus from entering the country and easing pressure on emergency response systems.

Previously, US citizens, nationals and green card holders were exempt from the 30-day Ebola travel restrictions introduced earlier this week under Title 42 public health authority.

The move comes after the World Health Organization raised the risk level of the rare Bundibugyo strain of Ebola spreading into a national outbreak in Congo to “very high” and declared the outbreaks in Congo and Uganda a public health emergency of international concern.

Reuters also reported that the CDC had earlier directed US citizens and lawful permanent residents returning from the affected countries to enter America only through Washington Dulles International Airport for enhanced health screening.

Health officials say the risk of Ebola spreading widely in the United States remains low. Earlier this week, the CDC confirmed that one American working in Congo tested positive for Ebola and was transferred to Germany for treatment.