By Elise Viebeck - 08/04/14 01:06 PM EDT
A widening outbreak of Ebola flu in West Africa has killed nearly 900 people and sickened more than 1,600, the World Health Organization (WHO) reported Monday.
Most of the deaths have been concentrated in Liberia, Sierra Leone and Guinea, where the disease began to wreak havoc earlier this year.
The current outbreak is the worst on record, and governments in West Africa are struggling to contain it despite help from the WHO and U.S. health officials.
Nigeria reported Monday that it has confirmed a second case of Ebola, indicating the disease is spreading there.
Ebola jumps from an infected person through direct contact with bodily fluids. People who contract the virus are usually healthcare workers, family members of someone who is sick or outsiders involved in burials.
The virus kills nearly all of its victims, and neither a vaccine nor a cure exist.
Of the two Americans who have been infected in West Africa, one has already been transported to the United States for treatment and the other will follow early Tuesday.
A chartered evacuation plane landed late Monday afternoon in Monrovia, Liberia, to carry missionary Nancy Writebol to a hospital in Atlanta, according to The Associated Press.