Ebola has officially hit the US. On Sunday, the Centers for Disease Control and Prevention confirmed that a nurse in Dallas contracted the vicious disease from a patient who was infected in Liberia and traveled to Texas before showing symptoms.
Ebola is still mostly concentrated in West Africa, and as long as the outbreak there continues, it's likely that the virus will keep popping up in other countries - though the risk of a widespread outbreak here remains very low.
"Germs have always traveled," Howard Markel, a professor of the history of medicine at the University of Michigan, told The New York Times. "The problem now is they can travel with the speed of a jet plane."
Here's a look at which countries have seen Ebola cases so far:
Only one area - West Africa - is in the real danger zone of widespread transmission. The healthcare system in that region is severely lacking, which has made the disease difficult to contain. And the international response was minimal until the outbreak had already spun out of control.
So far, Ebola hasn't spread much outside of the epicenter of the outbreak. Spain was the first country outside of Africa with a locally acquired case. The US has seen one local transmission so far - the Dallas nurse - and one death from someone who contracted the disease in Liberia and then started showing symptoms after he traveled to the US to visit family and friends. Thomas Eric Duncan died in Dallas last week.
The US, along with some European countries, has also seen some "medically evacuated" cases, meaning that people contracted Ebola in West Africa and were then evacuated to their home countries for care. These cases include an NBC cameraman as well as doctors and aid workers who were working in West Africa.
More than 4,000 people have died in what's been the worst Ebola outbreak the world has ever seen. The Ebola crisis is by far the most serious in Guinea, Liberia, and Sierra Leone, where more than 8,000 people have contracted the disease. Those numbers include 401 healthcare workers who have been infected; 232 of them have died.
As long as the outbreak rages on in West Africa, "we can't make the risk zero here," CDC Director Tom Frieden has said. "We wish we could."
Ebola's death rate in the current outbreak has been about 70%. The disease begins with flu-like symptoms and in many cases escalates to internal and external bleeding and organ failure.