The agency reiterated that the Canadians were being brought back to Canada early after it was discovered several people at the hotel where they were staying were infected with Ebola.
Earlier Wednesday the U.S. Centers for Disease Control revealed it had flown two CDC scientists back to Atlanta from Kailahun in response to the same incident.
The Public Health Agency had initially spoken of three infections there and while Wednesday's statement did not repeat that number, sources say that there are indeed reports of three sick people at the hotel.
The Public Health Agency would not grant interviews about the situation. Instead it released a six-paragraph statement late in the day saying the Canadians are in good health and believed to be at low risk of infection.
"As an added precaution, the employees will not be travelling on a commercial flight to Canada, will be monitored closely on their journey home and after they return to Canada, and will be in voluntary isolation," the statement said.
The Public Health Agency said for privacy purposes it won't release the names of the scientists or reveal when they are returning to Canada or their destination in Canada.
It said Canada remains committed to helping in the outbreak response and will send another lab team to Sierra Leone "once appropriate steps have been taken to ensure a safe living environment."
The WHO announced Tuesday it was temporarily removing its staff at Kailahun, after a Senegalese epidemiologist working as part of the WHO team contracted Ebola. He was deployed with the WHO through its Global Outbreak Alert and Response Network — known as GOARN. On Wednesday, the man was medevaced to Hamburg, Germany, for care.
Three WHO staff were sent to Sierra Leone's capital, Freetown, for rest and observation. But the U.S. Centers for Disease Control flew two people it had working at Kailahun back to the United States after one was confirmed to have had what is considered low-risk contact with a person who contracted Ebola.
The CDC did not identify the responder who had become infected at Kailahun, but it is believed to have been the Senegalese epidemiologist.
A spokesperson for the CDC said one of its people was at the end of a mission and due to come home, and the other was approaching the end of his or her time in the country. Neither is showing signs of being sick.
The person due to leave had worked in an office setting with the GOARN worker who became ill, Tom Skinner said.
"The person had a low-risk exposure. In other words they were near this person, within three feet" — roughly a metre — "at times for a prolonged period," he said, adding this interaction happened when the infected person was already feeling unwell.
People with Ebola are believed to be contagious only when they are sick and not during the time before symptoms commence. The time from exposure to evident infection can range from two to 21 days. The virus is transmitted through contact with body fluids.
The WHO declared the Ebola outbreak a public health emergency of international concern on Aug. 8. When it did, it issued a number of recommendations including one stipulating that people who are contacts of known cases should not fly on commercial flights during the 21 days in which they might be incubating the virus. The recommendation is aimed at preventing further spread of the virus.
Skinner said because of that recommendation, the agency chartered a plane to transport its two staff members home.
He noted the CDC remains committed to the fight against Ebola in West Africa. The CDC currently has 29 staff members in Sierra Leone, with nine more preparing to be deployed to the country.
The WHO's director of communications, Christy Feig, said in an interview Wednesday that the organization is investigating how the epidemiologist became infected.
The unit where he, the Canadians and the Americans were working did not treat patients; it was a support unit for a nearby treatment centre operated by Medecins Sans Frontieres (Doctors Without Borders).
"It could have been a straightforward thing; he was exposed in an accident with an infected patient, it could have been that simple," Feig said Wednesday in an interview from Liberia.
"But it also is a little unusual so we want to give it a close look so we can make sure there's not something about the setup there that's putting more people at risk."
Earlier this week a spokesperson for the Department of Foreign Affairs, Trade and Development said the federal government has been working on plans to repatriate Canadians from the Ebola zone of West Africa, in case the need arose.
"Considerable planning has been undertaken in the event that a Canadian becomes sick abroad and asks for assistance with repatriation," spokesperson Beatrice Fenelon said in an email.
"DFATD has identified commercial medical air evacuation companies to fly a sick person home to Canada and has been in discussion with provincial health ministries about where possible patients could safely receive care."
The WHO has not updated case numbers in a week and has said several times that it believes the figures it has underestimate the scope of the outbreak. Its last figures, from Aug. 20, suggest more than 2,600 people have been infected in this outbreak and more than 1,400 have died.
Health-care workers continue to make up an alarming percentage of the cases. As of Aug. 25, the WHO said there had been 240 infections in health-care workers, and more than 120 of those people had died.
In related news, the WHO announced Wednesday that it had been informed by the Democratic Republic of Congo that it has an Ebola outbreak as well. The WHO said there have been 24 suspected cases and 13 deaths.
The event appears not to be connected with the West African outbreak. The Democratic Republic of Congo has had multiple Ebola outbreaks since the virus first hit the world's radar in 1976.
The global health agency said the first case was in a woman who had butchered a bush animal. The woman later died. Neither she nor her contacts had a history of travel to the countries affected by the ongoing Ebola outbreak, nor are they known to have had contact with people from those countries.
The WHO said samples have been sent to laboratories in the capital, Kinshasha, and in Gabon for confirmation and, if positive, to determine the specific strain of virus responsible for the outbreak.