The highly virulent Ebola virus has seen a few major outbreaks since it first appeared in 1976 -- with the worst epidemic occurring in 2014. How does the virus spread, and what exactly does it do to the body? Alex Gendler details what Ebola is and why it's so hard to study.

Lesson by Alex Gendler, animation by Andrew Foerster. View full lesson:
http://ed.ted.com/lessons/what-we-know-and-don-t-know-about-ebola-alex-gendler