Health-care workers dress in protective gear recently at the ALIMA Ebola Treatment Unit in Nzerekore, Guinea. (Jane Hahn for The Washington Post)

Scientists are launching tests of two experimental Ebola vaccines in West Africa. In one of the countries, Guinea, they are turning to a method that helped wipe smallpox off the globe.

In the 1960s, as smallpox raged across parts of Africa, Asia and South America, the leading global strategy was to vaccinate masses of people against the disease. Smallpox, which is caused by the variola virus, spreads by direct contact or through droplets of saliva transmitted in a person's breath.

In Nigeria at about that time, a medical missionary named Bill Foege was faced with the challenge of containing a smallpox outbreak. He questioned the strategy of mass vaccinations and helped develop a different approach. It reflected his experience as a young man fighting forest fires in the Pacific Northwest. The thought was pretty simple: A fire can’t live without fuel or oxygen.

“And so you develop a ring around the fire,” he said in a recent interview. If you created a ring of immunity — in this case, of vaccinated people around each smallpox case — the disease could be wiped out much more efficiently, he believed. Foege and his team sent messengers into remote Nigerian villages and mapped out a plan to vaccinate people who had come into contact with infected patients.

The strategy also became known as the "ring vaccination theory" or  "surveillance" or "targeted" vaccination. "The whole emphasis is not on protecting people en masse. It's on being so intelligent that you can out-think the virus ... and look at who is at risk and where the virus is," Foege said. "You protect those people rather than other people."

The success was soon evident.

"What surprised us was how fast the smallpox stopped," Foege said. Within six months, the outbreak in Nigeria had been contained. Foege went on to lead the U.S. Centers for Disease Control and Prevention and later earned the Presidential Medal of Freedom, largely for his work in developing the theory of ring vaccination. The World Health Organization officially declared smallpox eradicated in 1980. It had killed, by some estimates, more than 300 million people in the 20th century alone.

Defeating smallpox "stands as one of the greatest accomplishments of the 20th century, if not one of the greatest human accomplishments of all time," two authors wrote in the Journal of Clinical Medicine Research.

Of course, the Ebola epidemic in West Africa is completely different from the smallpox epidemic. Roughly 9,000 people have died in the region since the outbreak began in Guinea in 2013, with a death rate of about 60 percent for those diagnosed with Ebola. Unlike smallpox, there is no proven vaccine.

The Ebola outbreak has significantly receded in recent months. That makes testing treatments and vaccines for Ebola more difficult, as scientists need a good number of cases to scientifically prove that any of these interventions work.

Officials from the World Health Organization plan to set up 190 "rings" in Guinea to test two experimental Ebola vaccines. That means that they need 190 Ebola patients, who make up the center of the rings. They plan to start the trial later this month.

A spokeswoman for the WHO, Daniela Bagozzi, said that Donald Henderson, who directed the organization's Global Smallpox Eradication Program, has given advice for the ring vaccination plans in Guinea.

Health workers plan to identify new Ebola cases and then find the recent contacts of those patients, including family members, neighbors and co-workers. Half of the rings will be vaccinated immediately, while the other half will be vaccinated several weeks later. If the vaccines work, the immediate group would likely develop fewer cases of Ebola.

One person eagerly watching the developments is Foege, who is now 78 and lives in Washington state. “This is exactly what I've spent my life doing,” he said, referring to his work with infectious diseases. “I know it can be stopped.”