Canada will temporarily bar foreign nationals who have recently visited the Democratic Republic of the Congo (DR Congo) from entering the country as the death toll from an Ebola outbreak continues to rise.

The measure takes effect at 11:59 PM on Monday and applies to foreigners who have been in DR Congo during the previous 21 days, the Public Health Agency of Canada (PHAC) announced on Sunday. Airlines have been ordered to prevent affected passengers from boarding flights to Canada.

Canadian citizens and permanent residents returning from DR Congo, Uganda or South Sudan will remain eligible for entry but must undergo health assessments and quarantine for 21 days. Canada initially suspended immigration documents for residents of the three countries in May after outbreaks of the Bundibugyo strain of Ebola were declared in DR Congo and Uganda.

PHAC said the new measures will remain in place until August 29, despite noting that the health risk posed by the disease to Canadians is considered low and that no travel-related cases have been reported in the country.

The agency said the move “is intended to increase the effectiveness and sustainability of border measures that can safely process travelers arriving in Canada, including our returning humanitarian workers.”

However, the World Health Organization (WHO) has warned that such restrictions risk fueling stigma against people from affected regions and African communities, stressing that Ebola transmission “is not determined by nationality or ethnicity.”

“Stigma discourages people from seeking care and can make outbreaks harder to control,” the WHO said in a statement last month.

Ebola spreads through direct contact with the blood or other bodily fluids of an infected person, or with contaminated objects and surfaces. DR Congo had recorded 2,344 confirmed infections and at least 930 deaths as of Saturday, according to the country’s Health Ministry. Uganda has reported 20 confirmed cases and two deaths. Its last patient was discharged on Thursday, beginning a 42-day countdown before the outbreak can be declared over.

No licensed vaccine or specific treatment exists for the Bundibugyo strain. Last week, Oxford University launched a Phase I human trial to assess the safety and immune response of its ChAdOx1 BDBV vaccine as a possible means of preventing the disease.

The US has barred American citizens departing DR Congo from returning directly, requiring them to spend 21 days in another country as part of measures it says are aimed at containing the outbreak.