A missionary organization announced that another American doctor has become infected with the Ebola virus, and the international group Doctors Without Borders warned Tuesday that the world is losing the battle against Ebola, The New York Daily News reported.

The missionary, a male obstetrician, has not yet been identified by the group Serving In Mission. The group did not specify how he contacted Ebola, since he did not work in an Ebola ward, but it can be spread through vaginal fluids.

Bruce Johnson, president of the group, said the organization was surrounding the missionary and Liberian nationals with prayer.

Organization President Joanne Liu said Doctors Without Borders is overwhelmed by the Ebola outbreak in West African countries. She said treatment centers offer barely anything more than palliative care and called on other countries to pitch in civilian and military medical personnel familiar with biological disasters like Ebola.

World Health Organization Director Margaret Chan warned that the outbreak would get worse before it will get better and would require a larger worldwide response. Though she thanked countries that lend a helping hand, she said more is needed from them. She also urged countries to step in to help if they haven't already.

Two Americans were evacuated to the United States last month after contracting Ebola in Liberia. The two received an experimental new drug called ZMapp and fully recovered. According to the manufacturer, it has depleted supplies of the drug and will take months to produce more.

The Ebola outbreak in West Africa has killed more than 1,500 people across Sierra Leone, Nigeria, Guinea and Liberia. Residents of the once-quarantined Liberian slum, West Point, are now allowed to leave the neighborhood. A curfew remains in effect.

The U.N. Food and Agriculture Organization warned that food goods in countries hit by Ebola are rising in price and will become scarcer because famers can't reach their fields.