Even if the CDC lab worker does contract Ebola, the possibility of an outbreak in the United States is incredibly unlikely. Eight of the nine Ebola patients treated in the United States have survived, and only one, Thomas Duncan, transmitted the disease to other people.
As Vox's Amanda Taub wrote earlier this year, the United States has the health infrastructure necessary to halt the disease in its tracks:
In the United States, we have everything we need to make that system work: the health-care workers, the facilities and equipment, the disease surveillance mechanisms, the public sanitation, the education and communications infrastructure — and the public trust that lets all of those individual components work together, as a whole system that is more powerful than the sum of its parts. By contrast, the worst-affected countries in this outbreak — Guinea, Liberia, and Sierra Leone — all lack those resources. Their systems don't work, and that has left thousands of people in terrible danger from this disease.