Jenneh became a nurse in Sierra Leone 15 years ago with the hope of saving lives in one of the world's poorest countries. Now she fears for her own after three of her colleagues died of Ebola.

Health workers like Jenneh are on the front line of the battle against the world's worst-ever outbreak of the deadly hemorrhagic fever that has killed 729 people in Sierra Leone, neighboring Liberia, Guinea and Nigeria so far.

With West Africa's hospitals lacking trained staff, and international aid agencies already overstretched, the rising number of deaths among health care staff is shaking morale and undermining efforts to control the outbreak.