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Nati Harnik, Associated Press
Dr. Ali Khan, Dean of the College of Public Health at the Nebraska Medical Center, speaks during a news conference in Omaha, Neb., Friday, Oct. 3, 2014, to discuss Ebola patient, journalist Ashoka Mukpo, who is expected to arrive from Liberia at the Medical Center on Monday.

OMAHA, Neb. — A plane carrying an American photojournalist who contracted Ebola while working in Liberia landed Monday in Nebraska, where he will undergo treatment for the deadly disease.

The specially equipped plane transporting Ashoka Mukpo landed at Eppley Airfield in Omaha at around 7:30 a.m. Monday. An ambulance was waiting to take him to the Nebraska Medical Center's specialized isolation unit, which is about a 20-minute ride from the airport.

Mukpo was working in Liberia as a freelance cameraman for NBC News when he became ill last week.

He is the fifth American to return to the United States for treatment since the start of the latest Ebola outbreak, which the World Health Organization estimates has killed more than 3,400 people. Meanwhile, a Liberian man with Ebola who started showing symptoms while visiting the U.S. is in critical condition at a Dallas hospital.

The Nebraska hospital's biocontainment unit was created in 2005 specifically to handle this kind of illness, Dr. Phil Smith, who oversees the unit, said in a news release Friday.

Mukpo's father, Dr. Mitchell Levy, told NBC Sunday that his son was "counting the minutes" until he could leave Liberia, but that he was not feeling that ill Sunday. Levy said the family was travelling from Rhode Island to Nebraska.

Doctors at the isolation unit — the largest of four nationwide — will evaluate Mukpo before determining how to treat him. They said they will apply the lessons learned while treating American aid worker Rick Sacra, who was allowed to return home to Massachusetts after three weeks, on Sept. 25.

Sacra received an experimental Tekmira Pharmaceuticals drug called TKM-Ebola, as well as two blood transfusions from another American aid worker who recovered from Ebola at an Atlanta hospital. The transfusions are believed to help a patient fight off the virus because the survivor's blood carries antibodies for the disease. Sacra also received supportive care, including IV fluids and aggressive electrolyte management.

Sacra was admitted to UMass Memorial Medical Center on Saturday after he came in complaining about a cough and low-grade fever and was put in isolation as a precaution. The hospital said weekend test results came back negative for Ebola, and the Centers for Disease Control and Prevention confirmed that Sacra's symptoms weren't caused by the virus.

In Dallas, another man who recently traveled to the U.S. from Liberia was listed in critical condition Sunday. Thomas Eric Duncan has been hospitalized at Texas Health Presbyterian Hospital since Sept. 28. Dr. Tom Frieden, the CDC's director, said he was aware that Duncan's health had "taken a turn for the worse," but he declined to describe Duncan's condition further.

The virus that causes Ebola is not airborne and can only be spread through direct contact with the bodily fluids — blood, sweat, vomit, feces, urine, saliva or semen — of an infected person who is showing symptoms.

Duncan arrived in Dallas on Sept. 20 and fell ill a few days later. Officials say 10 people definitely had close contact with Duncan and a further 38 may have been around him when he was showing symptoms of the disease.

Associated Press writers Nomaan Merchant in Dallas and Emily Schmall in Fort Worth, Texas, contributed to this report.