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FREETOWN, Sierra Leone -- A third top doctor has died from Ebola in Sierra Leone, a government official said Wednesday, as a leading American health official warned that the outbreak sweeping West Africa would get worse before it gets better.
The disease has already killed more than 1,400 people in Guinea, Liberia, Nigeria and Sierra Leone, and experts have said it could take months to bring it under control.
"I wish I didn't have to say this, but it is going get worse before it gets better," Dr. Tom Frieden said.
He is the director of the U.S. Centers for Disease Control and Prevention, and discussed the outbreak at the end of a visit to Liberia, where he described the situation as dire.
Frieden travels next to Sierra Leone, where the loss of a third senior doctor has raised concerns about the country's ability to fight the outbreak.
Dr. Sahr Rogers had been working at a hospital in the eastern town of Kenema when he contracted Ebola, said Sierra Leonean presidential adviser Ibrahim Ben Kargbo on Wednesday.
Rogers' death marks yet another setback for Sierra Leone, a country still recovering from years of civil war, where there are only two doctors per 100,000 people, according to WHO. By comparison, there are 245 doctors per 100,000 in the United States.
Health workers have been especially vulnerable because of their close proximity to patients, who can spread the virus through bodily fluids. WHO has said that at least 240 health workers have been infected in this outbreak, more than in any other. One of those is an epidemiologist working with the WHO in Sierra Leone, who has been evacuated for treatment in Germany.
"The international surge of health workers is extremely important and if something happens, if health workers get infected and it scares off other international health workers from coming, we will be in dire straits," said Christy Feig, director of WHO communications.
A team of two experts was sent Tuesday to investigate how the Senegalese epidemiologist became infected, said Feig. In the meantime, the WHO has pulled out its team from Kailahun, where he was working.
The epidemiologist had been doing surveillance work for the U.N. health agency, said Feig. The position involves coordinating the outbreak response by working with lab experts, health workers and hospitals, but does not normally involve direct treatment of patients.
There is no proven treatment for Ebola, so health workers primarily focus on isolating the sick. But a small number of patients in this outbreak have received an experimental drug called ZMapp.
Health officials in Liberia said two recipients of ZMapp in Liberia -- a Congolese doctor and a Liberian physician's assistant -- have recovered. Both are expected to be discharged from an Ebola treatment center on Friday, said Dr. Moses Massaquoi, a Liberian doctor with the treatment team.
The drug has never been tested in humans, and it is unclear if it is effective. Only a handful of people have received ZMapp in this outbreak, and some have recovered while others have died.
Other Ebola developments:
-- The World Health Organization said it was notified Tuesday of an unrelated Ebola outbreak in Congo. The agency said Wednesday that 13 of the 24 people sickened there have died.
-- The U.S. Agency for International Development announced it is giving an additional $5 million to provide health equipment and emergency supplies, train and support health care workers, and help build emergency response systems.
-- The Nigerian Ministry of Health has ordered all primary and secondary schools to remain closed until Oct. 13 to help ensure that Ebola does not spread any further in the country. Five people have died from Ebola in Nigeria, and officials have expressed optimism the disease can be contained.
-- Air France temporarily suspended its three flights a week to Sierra Leone because of the outbreak. The French national carrier is maintaining its flights to Conakry, Guinea, and to Lagos, Nigeria.