Health workers carry the body of an Ebola virus victim in Kenema, Sierra Leone. (REUTERS/Umaru Fofana)

The doctor leading Sierra Leone's fight against the deadliest Ebola outbreak in history has contracted the virus himself, government officials said.

Sheik Umar Khan, 39, was on the front lines of battling the disease that has so far claimed 632 lives in three West African states, according to the World Health Organization.

He is credited with treating more than 100 victims.

And now he is one himself.

In late June, Khan seemed keenly aware of the risk he faced. "I am afraid for my life, I must say, because I cherish my life," he told Reuters. "Health workers are prone to the disease because we are the first port of call for somebody who is sickened by disease.

"Even with the full protective clothing you put on, you are at risk."

Nurses treating Ebola cases at the government hospital in Kenema, one of the centers of the outbreak, went on strike Monday after three fellow nurses were believed to have died of the virus, according to the BBC.

Sierra Leone alone has suffered 206 deaths, with hundreds more affected. Doctors and public health officials are scrambling to combat the disease, which is spreading quickly in the eastern part of the country.

Sheik Umar Khan in June. (REUTERS/Umaru Fofana)

Those who can't be saved are being buried in makeshift graves near a treatment center. Some who die at home remain there until public health officials can be alerted.

Khan is being treated in a ward run by the medical charity Medecins Sans Frontieres (Doctors Without Borders) in Kailahun. The charity is also evaluating the Ebola case management center at the government hospital in Kenema and will report back to the Ministry of Health.

Sierra Leone's health minister, Miatta Kargbo, pledged to "do anything and everything in my power to ensure he survives," Reuters reported.

The virus, which is contracted by contact with infected bodily fluids of humans or animals, causes death in 90 percent of cases, according to the World Health Organization. Early treatment can, however, improve chances of survival.

It can incubate for up to 21 days before symptoms begin to arrive: First fever, pain and headaches, then diarrhea, vomiting and rashes. In some cases, bleeding both inside and outside the body might occur.

There is no known cure or vaccine, though several are being tested.

"We are running behind Ebola," said Anja Wolz, emergency coordinator with MSF, which runs the Ebola treatment center in Kailahun, according to the WHO. "We came too late when villages already had dozen of cases and right now we don't know where all chains of transmission are taking place."

[This post has been updated.]