This is how badly infectious epidemics have devastated humans in history (graphic)

See National Geographic for full graphic. 

Today, nations are struggling to get Ebola under control. This week saw New York City's first case, while the World Health Organization declared Nigeria and Senegal free of Ebola. (See "From Senegal and Nigeria, 4 Lessons on How to Stop Ebola.")

How much higher this epidemic's death toll might climb remains to be seen. In late September, the U.S. Centers for Disease Control and Prevention estimated that in a worst-case scenario, the total number of cases (not deaths) could reach 1.4 million by late January...