health headline of the year, ebola. one began as a single case in guinea last december has grown into an epidemic of unprecedented proportions. in the first of its kind maneuver, two aid workers, dr. kent brantly and nancy writebol were medevaced back to the united states. as 2014 comes to a close, the world health organization tallies more than 6,000 deaths among roughly 18,000 sick. the outbreak in west africa is far from over. but early stage vaccine trials are under way and they do look promising. >> my friend sanjay gupta. i wish him and his family a very merry christmas. as this clear comes to a close, check out more of our top ten list at cnn.com.