Contrary to the belief that the Ebola virus episode is over, health officials in Sierra Leone have reportedly confirmed two new cases on Thursday.

Two Ebola aid workers from the United States and Britain have been infected with the deadly virus in Sierra Leone, reports say.

According to the National Institutes of Health (N.I.H) in Maryland, US, the unidentified American became infected while working at a treatment center and had been ordered flown back to the United States in isolation in a chartered plane.

The worker will be admitted on Friday to the hospital at the Institutes of Health, the Institute said in a statement.

The N.I.H. hospital has treated one other Ebola patient: Nina Pham, a nurse infected while caring for a Liberian patient in Dallas. She recovered. Two other health workers with possible exposure to the virus were also treated at N.I.H., but turned out not to be infected.

However, British officials said a Royal Air Force plane left Sierra Leone carrying three British military health workers, of whom one has tested positive for Ebola. The other two were under observation for signs of infection.

All three will be taken to the Royal Free Hospital in northwest London, which has a specialized isolation unit to treat Ebola patients. Two nurses, the only other Britons who have contracted the virus, survived infection last year after being treated at the hospital.

The World Health Organization said Thursday that the number of deaths in the Ebola epidemic that has afflicted Guinea, Liberia and Sierra Leone had surpassed 10,000.

While the number of new cases has fallen drastically in all three countries in recent months — and reached zero in Liberia last week — the transmission of the disease has been a resilient problem in the other two.