The last week has brought some unfortunate firsts for the United States.

A patient from Liberia became the first person to die of Ebola in the U.S. and a nurse treating him became the first person infected with the virus on U.S. soil.

The Texas nurse, Nina Pham, is unlikely to be the last person to contract Ebola in the country. About 70 other hospital staff members were involved in the case of Ebola patient Thomas Eric Duncan. Researchers targeted the United States as a likely place for future cases, given the amount of air travel to the country. The Centers for Disease Control and Prevention urged hospitals to "think Ebola."

Ebola has killed more than 4,000 people in West Africa, according to reports from the World Health Organization, and those numbers are expected to increase. In the next two months, the organization reported there could be 10,000 new Ebola cases each week. The crisis prompted Facebook CEO Mark Zuckerberg and his wife to donate $25 million to the CDC Foundation.

Although this is the most serious outbreak of Ebola on record, there have been plenty of cases before now. Some previous outbreaks saw a more deadly virus. In previous outbreaks, the percentage of deaths for cases has been between 25 and 90. About half of cases in this outbreak result in death, according to the World Health Organization.



Cases have been concentrated in Liberia, Sierra Leone and Guinea. The number of cases has escalated steadily since May. The WHO declared the outbreak an international health emergency in August.

Courtesy WHO

The maps below, from WHO, show cases of Ebola by country.



Courtesy WHO

As shown in the key below, the center of the circles show the cases occurring in the past 21 days. In many areas, the circles are completely dark red, showing the fast spread of the virus.

Courtesy WHO

Courtesy WHO

Through a collaboration with Northeastern University, the ISI Foundation, and others, researchers have built a model to predict the progression of the disease in West Africa, if the disease continues at its current pace.

Courtesy Mobs Lab

Using flight patterns, they also predict which countries are likely to see Ebola cases in the future.

Courtesy Mobs Lab

They calculated the importation risk for Ebola without a travel reduction and with an 80 percent travel reduction. The United States is at the top of both lists.

Courtesy Mobs Lab

This map from Tennessee Department of Health shows the health evaluation levels for patients returning from foreign countries. West African countries have a level three warning to avoid nonessential travel. For countries in the Middle East, the map advocates enhanced precautions for Ebola.