The nuns in the hospital at the center of the outbreak put up a sign that said "anybody who passes this fence will die." CDC/Joel G. Breman, M.D., D.T.P.H. This summer, a small Ebola outbreak in the Democratic Republic of the Congo was quickly and effectively contained — clear proof of how much scientists have learned about the deadly virus since it appeared in 1976.

The most recent outbreak occurred in a province that neighbors a small village called Yambuku, where the disease first reared its head.

When Ebola started to kill patients in a missionary hospital, a Flemish nun was infected and samples of her blood were sent to Belgium. Scientists soon realized they were dealing with something unknown.

After a harrowing experience with the virus in the lab, Peter Piot, a 27-year-old doctor who was one of the first to examine Ebola, left his pregnant wife in Belgium and set off for the Congo, then called Zaire, to track down the source of the outbreak. There he joined researchers from around the world in a terrifying hunt for the origin of the disease.

We still don't know what the original host of Ebola was, and the highly contagious disease continues to threaten devastation in the areas where it appears. Between 2014 and 2016, the world saw the biggest and most complex Ebola epidemic ever.

Piot wrote about his experience traveling in the Congo in his book "No Time to Lose: A Life in Pursuit of Deadly Viruses." Using photos from the CDC's Public Health Image Library, we've illustrated the team's first several expeditions.