A health worker wearing protective gear at an Ebola Donka treatment center in Conakry, capital of Guinea, in December. (Cellou Binani/AFP)

There was a time not long ago when Tom Frieden looked at Conakry, the capital of Guinea, and saw the same conditions that allowed Ebola's terrible march through Monrovia and Freetown, the capitals of Liberia and Sierra Leone, where the virus's toll has been much greater.

"I was terrified Conakry was going to be the next Freetown or Monrovia," the director of the Centers for Disease Control and Prevention said Friday after returning from a trip to Guinea.

That didn't happen. "They've walked back from the precipice of a massive city-wide outbreak," he said. In part, that was because Conakry had a better disease reporting system than the other two West African cities when the worst Ebola outbreak on record began early last year. And in part, he said, it was because Guinea's public health system was a little bit more robust than Liberia's or Sierra Leone's.

Substantial progress has been made, Frieden said, especially in getting the virus out of Guinea's forest lands.

[Guinea, ground zero for Ebola outbreak, hopes the end is near]

Still, Ebola is smoldering in Guinea, resisting the determined efforts of local and western health workers to stamp it out as they have in Liberia or bring it further under control as they have in Sierra Leone. Liberia discharged its last Ebola case March 5 and has not seen a new once since. Sierra Leone reported 58 new confirmed cases in the week before March 8, according to the World Health Organization but Frieden said 60 to 80 percent of them are the result of known contacts, a sign that authorities are getting a handle on the outbreak.

Guinea also had 58 new cases that week, according to the WHO, but there the prospects aren't as bright, Frieden said. Guinea never experienced the big spike in cases that Liberia and Sierra Leone suffered during the heights of their epidemics, but Ebola has proved quite persistent there. (Overall, Ebola has infected 24,509 people and killed 10,096 of them, all but a handful in the three West African nations.)

Frieden pointed to two main problems. (My colleague Amy Brittain also explored this terrain in a story last month):

• The sheer size of Guinea makes the effort more difficult. The country is physically about the size of Liberia and Sierra Leone combined, and it has more people than the other two combined.

• Resistance to anti-Ebola campaigns in Guinea has been greater than in Liberia or Sierra Leone. In September, eight people were killed with machetes and stones in the village of Womey when they arrived as part of a “sensitization” effort. According to the WHO, during one recent week, residents of 27 towns in Guinea resisted Ebola-eradication efforts.

[As Ebola recedes, Liberian capital begins to come to life]

The reasons, Frieden said, can be different in each village. In one, a burial team may have been insensitive. In another, some residents may have fallen ill after a team disinfected with chlorine, prompting villagers to believe the virus had been sprayed on their homes. Frieden said he heard the story of a soldier who threatened to kill health workers if his Ebola-stricken wife didn't recover; when she did, residents attributed her survival to the threat.

Some signs of a turnaround are present, he said. Imams have gotten involved in the effort, and more aid teams are being allowed into communities to conduct tests and isolate the infected.

"We'll take things one day at a time, and until it's out of the region, all of the countries remain at risk," Frieden said.

"There's no magic bullet," he added. "We need to do what we're doing, consistently, quickly, and stick with it."