The rapid spread of a rare strain of Ebola in Central and East Africa now constitutes the third-largest Ebola outbreak on record. There have been more than 1,000 confirmed cases and hundreds of fatalities so far, with most cases concentrated in eastern Democratic Republic of Congo.
Here's what to know about what's driving the current Ebola outbreak, the scale of the crisis, and what it means for the state of global health infrastructure and preparedness: