(ABC News) -- The relief organization whose doctor is being treated for Ebola in Liberia announced today that another American who was working at the same facility has tested positive for the disease.
Nancy Writebol is employed by SIM in Liberia and was helping the joint SIM/Samaritan's Purse team that is treating Ebola patients at the Case Management Center in Monrovia.
SIM manages ELWA Hospital in Morovia, and the two organizations have been working closely to combat Ebola since the current outbreak began in Liberia in March.
Writebol is married with two children.
Dr. Kent Brantly, 33-year-old American doctor who was treating Ebola patients, also tested positive for the deadly disease. He was reported to be sitting up in his isolated hospital bed and working on his computer after he contracted the deadly virus this week.
Brantly, from Fort Worth, Texas, has been living and working in Monrovia, Liberia since last October, when he moved there with his wife and two young children as part of a post-residency program set up by Samaritan's Purse, a nondenominational evangelical Christian organization that aims to provide international aid.
The World Health Organization reported that 964 people in three African countries have contracted the disease and 603 have died from it, as of July 12. The Ebola virus is spread through close contact between people, including bodily fluids and secretions, and health workers are one of the most at risk populations.
On Saturday, Dr. Samuel Brisbane, a senior doctor at Liberia's largest hospital, became the country's first doctor to die of Ebola.