They also say that Nebraska is the largest of the 4, with 10 bio-secure units... so our setup to contain major outbreaks has 40 or less level 4 biocontainment beds throughout the country....He was sent to Nebraska because the University of Nebraska Medical Center has a high-level biocontainment patient care unit, one of four in the nation.
Another one is in Atlanta, where the two missionaries were sent. Other units are in Montana and Maryland.
The guy in Dallas is in Dallas because that's where he arrived from out of the country and that's where he started showing symptoms.
Here's a story about the Nebraska unit.