AUDIE CORNISH, HOST:

Now to the Democratic Republic of Congo, where for months health workers have been struggling to contain an Ebola outbreak. Despite the fact that more than 100,000 people have been vaccinated, there's been a surge of new cases. And more than 1,300 people have been infected so far. The biggest obstacle to stopping the outbreak - armed groups who keep attacking health workers. In just the last few days, there were two assaults. Here to tell us more is NPR's Nurith Aizenman. Welcome to the studio.

NURITH AIZENMAN, BYLINE: Hi, Audie.

CORNISH: Give us the latest on these attacks first.

AIZENMAN: Well, the first one was on Friday afternoon. It was at a local hospital in a city called Butembo. That's one of the current epicenters of the outbreak. And about 20 members of one of the local Ebola response teams were having a meeting. And witnesses say two gunmen burst in. They took everyone's cell phones and other equipment. They started shooting, injured two people. And they killed the team leader. His name was Dr. Richard Valery Mouzoko. He was an epidemiologist from Cameroon who'd been deployed by the World Health Organization to help fight Ebola.

And then, just a few hours later, there was an attack on another local command center. This one was at a hospital in a nearby suburb called Katwa. It's one of the worst hotspots in the outbreak zone. And this one was around 3 a.m. Saturday morning. Four people tried to set fire to that command center. Police fought them off. They killed one assailant, and they captured the rest.

CORNISH: Are these centers being targeted on purpose? And if so, how come?

AIZENMAN: It seems so, yes. And it's not clear exactly who was behind each of these attacks. But I spoke with Dr. Michel Yao, who is leading the Ebola response for the World Health Organization. And he says witnesses in that first attack told him that the gunmen were shouting, Ebola doesn't exist; you're just here to make money off of us. And it fits into a larger problem of mistrust in the local population. There have been years of armed conflict in this part of Congo. And people feel victimized by the government. So they don't trust authorities and, by extension, health workers.

CORNISH: What does this mean for the effort to try and contain the outbreak?

AIZENMAN: Well, there's a lot of concern because this is just the latest in a series of violent incidents that directly target health workers. Since February, two Ebola treatment centers have been attacked. Dr. Mouzoko, the doctor who was killed on Friday, he had only arrived four weeks ago. And he apparently told colleagues that he was really worried. He's left behind a wife and four children in Cameroon. And so each time there's been an attack, the health workers need to regroup. They slow down their efforts to vaccinate people who've been exposed.

And then you see the effect in the outbreak. It gets worse. Basically, more people start to get sick. And, you know, to give you an example, in February, just before these attacks on the Ebola treatment centers started, they were seeing about 30 new cases a week. And then this month, we're already up to 70 new cases every week, even as high as 100 new cases every week.

CORNISH: If this violence continues, is there a chance that the outbreak could grow into a catastrophe similar to what we saw in 2014 in some West African countries?

AIZENMAN: There are some really important differences. First of all, the WHO and the government have been on this from the beginning. There's also a vaccine now, which has been a game changer. As you noted, they've managed to get more than 100,000 people to take it. And the evidence is it's highly effective. So there are still reasons to be hopeful, despite this latest violence.

CORNISH: That's NPR's Nurith Aizenman. Thank you for explaining it to us.

AIZENMAN: Glad to do it. Transcript provided by NPR, Copyright NPR.