Could the Ebola outbreak spread to the U.S.?

[link to thechart.blogs.cnn.com]

Could this outbreak spread to the U.S. or other distant countries?

Experts think it's unlikely the current outbreak would spread to the United States. While the only example of transmission of Ebola in the United States came with the importation of research monkeys (no humans were sickened), there was a situation four years ago where two tourists traveling in Uganda were infected with Marburg hemorrhagic fever.

Both patients returned to their home countries, according to the CDC. One survived and the other died, but nobody else was infected because proper protections were taken during treatment.

When is an outbreak considered 'finished'?

The incubation period for Ebola is two to 21 days, according to the WHO. Health officials tell CNN an outbreak is considered to be over following two incubation periods after the last person becomes ill - a total of 42 days.