When should we be worried about the Ebola outbreak? According to an article on the NPR website, it's when the virus is spreading in a crowded urban environment that's a major transportation hub and has dilapidated, ill-equipped healthcare facilities.
Unfortunately, that's what's happening right now in the northwest of the Democratic Republic of the Congo, the article said.
The epicenter of the outbreak is in an extremely rural, remote part of the Equateur province. But patients have appeared up nearly a hundred miles away in Mbandaka, a city of more than a million on the banks of the Congo River.
When there are cases in urban areas, the number of contacts can amplify much more quickly. The increase in the transmission can be much more exponential rather than linear.