A second U.S. citizen working in Liberia has tested positive for the Ebola virus, a charitable organization working in the county said on Sunday. The latest victim is Nancy Writebol, who was helping a joint Serving In Mission/Samaritan's Purse team in Liberia to help treat victims of the deadly disease at a Case Management Center in Monrovia, according to a statement from Samaritan’s Purse. Writebol was with her husband in the country working as a personnel coordinator for SIM, according to the organization’s website.

Meanwhile, an American doctor earlier infected with the disease was receiving intensive treatment Sunday and was in stable condition, even talking to his medical team and working on his computer, a spokeswoman for Samaritan’s Purse said. Dr. Kent Brantly, 33, is the medical director for the North Carolina-based Samaritan's Purse. Both Brantly and Writebol are in stable condition and receiving intensive treatment, said Melissa Strickland, a spokesperson for the group.

The highly-contagious virus is one of the most deadly diseases in the world. The World Health Organization said the latest outbreak is the largest ever recorded, killing more than 670 people in Liberia, Guinea and Sierra Leone since it began earlier this year.

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— The Associated Press