Health workers in protective gear pose at the entrance of the Ebola treatment unit of the John F. Kennedy Medical Center, in the Liberian capital Monrovia, on October 13, 2014. Health workers across Liberia went on strike on Monday to demand danger money to care for the sick at the heart of a raging Ebola epidemic that has already killed dozens of their colleagues. Doctors, nurses and carers in west Africa are on the frontline of the worst-ever outbreak of Ebola, which has killed more than 4,000 people, mostly in Guinea, Sierra Leone and the hardest-hit, Liberia. [AFP PHOTO / ZOOM DOSSO]