10/06/2014 11:41 EDT | Updated 12/06/2014 05:59 EST

Ebola update: Centers for Disease Control news conference

The U.S. Centers for Disease Control and Prevention (CDC) is giving another update on Ebola, as a fifth American to contract the virus in West Africa arrived back home for treatment on Monday.

A private plane carrying Ashoka Mukpo, a freelance cameraman for NBC News who contracted Ebola in Liberia, landed in Omaha en route to the Nebraska Medical Center, NBC reported. 

Dr. Thomas Frieden, director of the CDC, said on Monday said his agency would work "very closely" with the Nebraska hospital, which treated another Ebola patient in recent weeks.

Meanwhile, Dallas Ebola patient Thomas Eric Duncan remained in critical condition, Frieden said.

Duncan became ill after arriving in Texas from Liberia two weeks ago, heightening concerns that the worst Ebola epidemic on record could spread from West Africa, where it began in March.

Frieden said health officials were closely monitoring 10 people who had contact with Duncan and are considered at greatest risk. Another 38 people who potentially had contact with Duncan are also being tracked, he said.

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.

It has killed more than 3,400 people since it began in West Africa in March and has now begun spreading faster, infecting almost 7,500 people so far.