A leading physician in Sierra Leone's fight against Ebola has died from the disease, an official said.
The news came as it emerged that another top doctor had been considered to receive an experimental drug but did not get it and later died.
Ebola has killed more than 1,000 people in the current West African outbreak that has also hit Guinea, Liberia and Nigeria.
Many of the dead are health workers, who are often working with inadequate supplies and protection.
But despite the large number of deaths and infections among Africans, only two Americans and a Spaniard have received ZMapp, the unproven and experimental anti-Ebola drug made in the United States. That has stoked debate about ethics on who should be given the limited experimental treatment.
Doctors considered giving ZMapp to Sheik Humarr Khan, the chief doctor treating Ebola in Sierra Leone who had come down with the dreaded disease, but eventually decided against it, officials at the World Health Organisation (WHO) said.
WHO then tried to airlift Dr Khan out of the country, but "his condition had deteriorated too much to be transported safely". He died on July 29.
Doses of ZMapp for two Liberian doctors could arrive as soon as today in Liberia, according to the country's health minister Walter Gwenigale. They would be the first Africans known to receive the treatment.
The company that makes the drug, Mapp Pharmaceuticals, has said that its supplies are now exhausted, and it would take months to make even a modest amount.
Canada announced yesterday it would donate 800 to 1,000 doses of its experimental Ebola vaccine developed by the Public Health Agency of Canada to the WHO.
Dr Gregory Taylor, deputy head of the agency, said: "The trouble is, of course, with this very, very limited number of vaccines, who would you give that to?"
He said the agency has been advised that it makes the most sense to give the vaccine to health care workers in Africa who are among the most vulnerable because of their close contact with Ebola patients.
Meanwhile, yet another doctor in Sierra Leone, Modupeh Cole, died today, according to Sidie Yayah Tunis, director of communications for the Ministry of Health and Sanitation. Dr Cole, trained in the US, was one of the top doctors working in the Ebola isolation ward in Connaught Hospital in Freetown, the capital. He tested positive for the disease last week and was transferred to the eastern district of Kailahun, where Doctors Without Borders is running a treatment centre.
Dr Cole's sickness spread fear throughout the hospital where he worked, and staff there went on strike on Friday and Saturday after learning that he had tested positive for the deadly disease. They returned to work on Sunday.
Both Dr Cole's and Dr Khan's deaths are a major blow to Sierra Leone's health system, which is struggling to cope with the deadly outbreak.
The outbreak, which was first identified in March in Guinea, has strained the resources of the poor West African countries it has hit and of the international community, which is struggling to mobilise enough qualified doctors.
There is no known cure or licensed treatment for Ebola.