There are signs that the Ebola outbreak in the Democratic Republic of Congo may not be as big as was once feared, World Health Organization officials indicated Thursday.

Fourteen suspected cases have tested negative for the deadly virus, Alison Clements-Hunt, a WHO spokeswoman currently in Likati, the epicenter of the response, told STAT in an interview.

So far there have been two confirmed cases, four probable cases, and four deaths. Another 40 people are currently listed as suspected cases, said Clements-Hunt. Roughly 300 people who are contacts of known or suspected cases are being monitored to see if they develop symptoms.

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Clements-Hunt cautioned, though, that in an outbreak the net is cast wide to try to find anyone who might have Ebola, so that they can be isolated and tested. People who are sick with Ebola but are missed by surveillance can infect family members; if they die and are buried in traditional burial rites, those attending funerals can also be infected.

In the early stages of Ebola, symptoms are vague and could be misattributed to other conditions. In an outbreak, it is not uncommon for some suspect cases to later test positive for malaria, say, and negative for Ebola.

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A mobile laboratory is now operating in Likati, Clements-Hunt said. That will speed up the process of determining the actual scale of the outbreak. A response team of about 50 people from the DRC ministry of health, WHO, UNICEF, and Doctors Without Borders are in Likati, she said.

Among those who tested negative are five people who were being cared for in the Ebola treatment unit that was set up in Likati, Clements-Hunt said. Four have been released; one is still sick with something else and needs medical care.

Given what appears to be the limited scope of the outbreak, the use of an experimental Ebola vaccine may not be required.

“For the time, there doesn’t seem that there was really a necessity to do so. I hope it remains the case,” Dr. Marie-Paule Kieny, a WHO assistant director-general, told STAT.

That said, Kieny confirmed planning continues to allow for deployment of vaccine, if the government of DRC asks for it. But it may not, she acknowledged.

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“The logistics, all the preparations are moving forward, but you can imagine that without indication that this is spreading, that the government may decide that maybe it’s not reasonable to start a big vaccination operation. And actually, you don’t know who you would vaccinate,” Kieny said from Geneva.

The logistics of getting the vaccine to this remote part of DRC would be substantial. Clements-Hunt said getting from one village to another in this part of the country is incredibly difficult; there are no roads and response workers are being ferried along jungle paths on motorbikes.

“This is in the middle of nowhere,” said Kieny. ‘’It’s not a routine operation, so in order to go for it, they must be really sure that this is worth it.”

Some observers have questioned why the experimental Ebola vaccine, which was tested in Guinea in 2015, hasn’t been immediately sent to the DRC. There have been reports the government was hesitant about using an unlicensed product.

Kieny said this outbreak has galvanized awareness among the organizations that respond to Ebola outbreaks that the groundwork for use of the vaccine must be laid in advance in at-risk countries — places where Ebola outbreaks have happened in the past.

Regulatory agencies need to be asked to pre-approve vaccine use in emergencies; ethics committees that greenlight emergency use authorizations have to be asked to do this work in advance.

“This will move ahead as soon as this event is closed,” Kieny said. “After that we are having discussions about finalizing the preparations, making sure the protocol has been submitted in all the countries.”

An earlier version of this story incorrectly stated the surname of WHO spokeswoman Alison Clements-Hunt.