Officials have decided to evacuate volunteers from the ebola-stricken regions of Liberia, Sierra Leone, and Guinea, after two Americans were stricken by the deadly virus. As reported by CNN, the two victims are improving slightly, but remain in serious condition.

Two American aid workers have contracted the deadly ebola virus in Liberia as the outbreak continues to worsen in West Africa. Over 670 people have died since March in Guinea, Sierra Leone, and Liberia. NPR reports that the virus has probably now spread to Nigeria.