In this photo taken on Sunday, Sept. 7, 2014, a health worker, left, uses a thermometer to screen a man at a makeshift road block run by Guinean security forces outside the town of Forecariah, Guinea
Doctors Without Borders shuttered one of its Ebola treatment centers in Guinea in May. They thought the deadly virus was being contained there.
The Macenta region, right on the Liberian border, had been one of the first places where the outbreak surfaced, but they hadn't seen a new case for weeks. So they packed up, leaving a handful of staff on stand-by. The outbreak was showing signs of slowing elsewhere as well.
Instead, new cases appeared across the border in Liberia and then spread across West Africa, carried by the sick and dying. Now, months later, Macenta is once again a hotspot.
The resurgence of the disease in a place where doctors thought they had it beat shows how history's largest Ebola outbreak has spun out of control.
It began with people leaving homes in Liberia to seek better care or reunite with families back in Guinea, a pattern repeating itself all over.
"Currently in Guinea, all the new cases, all the new epidemic, are linked to people that are coming back from Liberia or from Sierra Leone," said Marc Poncin, the emergency coordinator for Doctors Without Borders in Guinea.
The epidemic also has touched Nigeria and Senegal while killing more than 2,000 people across West Africa. Never before has the disease struck such a densely populated region, where so many people are on the move. For four decades, the virus struck in relatively remote areas, where doctors could quickly isolate communities and stop its spread.