The head doctor who was leading the fight to control the deadly tropical virus Ebola has caught the disease himself in Sierra Leone, the government said Tuesday. The outbreak has killed 206 people in the West African country, with 90 percent of infected patients dying since there is no cure or vaccine.

Sheik Umar Khan, 39, has been hailed as a "national hero" by the health ministry for fighting the deadly virus, Reuters reported. Some of Africa's poorest countries are experiencing extreme strain on the health systems as more than 600 people have died from the illness across Guinea, Liberia and Sierra Leone, according to the World Health Organization.

Khan, a Sierra Leonean virologist credited with treating more than 100 Ebola victims, has been transferred to a treatment ward run by medical charity Medecins Sans Frontieres, according to the statement released late on Tuesday by the president's office. Describing Khan as a national hero, Health Minister Miatta Kargbo said she would "do anything and everything in my power to ensure he survives".

In late June, Khan told Reuters that he was anxious and worried about contracting the disease while treating infected patients. "I am afraid for my life, I must say, because I cherish my life," he said in an interview, showing no signs of ill health at the time. "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."

Additionally, three nurses working alongside Khan in the same Ebola treatment center died from the disease three days ago, according to Reuters.

The Ebola outbreak started in Guinea's remote southeast in February and has since spread across the region. Symptoms of the highly infectious disease are diarrhea, vomiting and internal and external bleeding.