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.
In previous outbreaks, a cleared pocket like Macenta would be easy to keep clear.
This time, the virus is traveling effortlessly across borders by plane, car and foot, shifting from forests to cities and springing up in clusters far from any previously known infections. Border closures, flight bans and mass quarantines have been ineffective.
"Everything we do is too small and too late," said Poncin. "We're always running after the epidemic."
Ebola has been able to follow its own course because West Africa lacks the health care workers it needs to monitor potential carriers and train communities in how to avoid catching the disease. People in contact with the sick have evaded surveillance, moving at will and hiding their illnesses until they infect others in turn. Whole villages, stricken by fear, have repeatedly shut themselves off for days or weeks, giving the virus more opportunities to whip around and skip someplace else.
Dr. Peter Piot, who co-discovered Ebola, said Ebola isn't striking in a "linear fashion" this time. It's hopping around, especially in Liberia, Guinea and Sierra Leone.
"The epidemic is now so vast and so extensive that one should consider that in the three (hardest-hit) countries, everybody is now at risk and it won't be over until the last case has survived and six weeks have passed," said Piot, who runs London's School of Hygiene and Tropical Medicine.
In mid-August, Guinea's health ministry announced 30 new cases in the Macenta region, the first recorded in months. Many were Guinean citizens who had been living in Liberia and were therefore allowed to return through closed border crossings. These returnees infected their families and neighbors, and so now there is active transmission in Macenta, said Michael Kinzer, who has led the U.S. Centers for Disease Control and Prevention's team in Guinea in recent weeks.
Doctors Without Borders has returned to Macenta as well, opening a transit center more than a week ago at the site of its old clinic where it screens patients. As of the beginning of this month, the Health Ministry said 45 people from Macenta were being treated at an expanded treatment center at Gueckedou. The charity would like to open treatment centers in both towns, but it does not have enough staff.
Authorities are now restricting access to the region's main city, also called Macenta, where fear has again taken hold.
"I have the impression that time has stopped in Macenta, that the city has shrunk," said Siniman Kouroumah, a 42-year-old teacher. "We are afraid to walk the city, to eat anywhere, to drink anywhere."
Poncin said he, too, has felt a shift, but for the better: People in Macenta are now afraid of dead bodies, running away from them rather than scooping them up for traditional burials. Villagers who used to throw stones at the health workers tracing contacts now seek their help.
Communities in many parts of Guinea are Ebola-free now, said Dr. Tom Frieden, the CDC's director, said on a recent visit to Guinea. "The challenge is that the region is really one entity, and it's so important that we get it right in all places."
"This is really the first epidemic of Ebola the world has ever known," Frieden said. "By epidemic what we mean is it's spreading widely through society, but not spreading through new ways according to everything we know. It's spreading from just two roots: people caring for other people in hospitals or homes, and unsafe burial practices where people may come in contact with body fluids of someone who has died from Ebola."
Getting it right in all places requires simultaneously imposing the same three measures anywhere Ebola appears, Poncin said: isolating the sick, tracing and monitoring everyone they have come into contact with, and ensuring infected bodies are buried safely.
Guinea is doing this fairly well, but Sierra Leone isn't doing enough, and Liberia is barely doing any contact-tracing, Poncin said.
That means officials don't know where people are at risk, making it almost impossible to prevent or at least contain new cases. The World Health Organization says it believes that the true spread in hard-hit areas may be two or four times bigger than what's known.
And if Liberia and Sierra Leone aren't keeping up, the public health work in Guinea - and Nigeria and Senegal - is for naught.
"As long there is one case of Ebola virus disease anywhere in the world and people are allowed to travel," Nigeria's health minister, Onyebuchi Chukwu, said recently, "every country in the world remains at risk."