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The Ebola virus is spreading exponentially across Liberia as patients fill taxis in a fruitless search for medical care, the World Health Organization said Monday.

In Sierra Leone, a doctor working for WHO tested positive and was preparing to be evacuated from the country. Meanwhile, the newest U.S. patient, a doctor infected in Liberia, was feeling a little better and could even eat a little, doctors treating him in Nebraska said.

The various reports illustrated in the clearest possible way the disparities driving the epidemic in West Africa, where there’s almost no medical system structure. The three patients evacuated to the United States have all begun to recover quickly once they get good supportive care, which includes around-the-clock nursing care and good nutrition.

WHO and other groups have been warning that the situation in Liberia and Sierra Leone and Guinea is dire. It’s especially bad in Liberia, WHO said Monday.

“Transmission of the Ebola virus in Liberia is already intense and the number of new cases is increasing exponentially,” WHO said in a statement.

"No free beds for Ebola treatment exist anywhere in the country.”

“In Monrovia, taxis filled with entire families, of whom some members are thought to be infected with the Ebola virus, crisscross the city, searching for a treatment bed. There are none. As WHO staff in Liberia confirm, no free beds for Ebola treatment exist anywhere in the country.”

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For example, in Montserrado county, 1,000 beds are urgently needed but only 240 beds are available. WHO has said more than 3,600 people have been infected with Ebola in this West African epidemic, and 2,000 have died, but the organization predicts as many as 20,000 will be sickened before it’s over. Half of those infected have been dying.

“According to a WHO staff member who has been in Liberia for the past several weeks, motorbike-taxis and regular taxis are a hot source of potential Ebola virus transmission, as these vehicles are not disinfected at all, much less before new passengers are taken on board,” WHO said.

“When patients are turned away at Ebola treatment centers, they have no choice but to return to their communities and homes, where they inevitably infect others, perpetuating constantly higher flare-ups in the number of cases.”

The need for beds, supplies and staff have “completely outstripped” capacity, both of the Liberia government and of outside groups such as Who and Medecins Sans Frontieres (Doctors Without Borders) to help.

Healthcare workers are being especially hard hit. “Some 152 health care workers have been infected and 79 have died,” WHO said. When the outbreak began, Liberia had only one doctor to treat nearly 100,000 people in a total population of 4.4 million people. Every infection or death of a doctor or nurse depletes response capacity significantly.”

"Motorbike-taxis and regular taxis are a hot source of potential Ebola virus transmission."

One WHO doctor in Sierra Leone is sick and will be sent out of the country for treatment, WHO said, but declined to say where the doctor was from.

Three of the healthcare workers affected were American medical missionaries working for the groups Samaritan’s Purse and SIM USA in Monrovia. All three were evacuated to the U.S. Dr. Kent Brantly and Nancy Writebol have recovered, while Dr. Rick Sacra is being treated at the University of Nebraska’s special biocontainment unit.

Debbie Sacra said her husband, a 51-year-old family physician, was eating and listening to music while he receives an experimental drug.

“He had some breakfast this morning, which is a change,” Debbie Sacra said in a statement. “He hasn’t been able to eat much since he got here, but he had some toast and apple sauce. He also tolerated the research drug well — better than he had the previous doses he was given.”

The hospital hasn’t said what treatment Sacra is receiving. Brantly and Writebol each received one treatment course of ZMapp, an experimental drug made by Mapp Biopharmaceutical Inc, but doctors stress they cannot tell if it helped.

“It’s hard to derive a lot of meaningful data from the care of just two patients,” said Dr. Aneesh Mehta, one of the medical team at Emory University Hospital who treated Brantly and Writebol. High quality nutrition given intravenously may have helped, Mehta said, as did carefully balanced fluid replacement formulas. Ebola patients often suffer intense vomiting and diarrhea.

The epidemic has demonstrated “how one disease outbreak can cause a whole country to go into crisis,” said Dr. Barbara Knust, team leader for the U.S. Centers for Disease Control and Prevention’s Ebola response.

“The Ebola outbreak has just driven home the inadequacy that’s there,” Knust told an American Society for Microbiology meeting.