Beni, August 11, 2018,(AltAfrica) — Armed groups, dense populations and mass displacement make Congo’s latest deadly outbreak of the Ebola virus more challenging than ever to contain, the World Health Organization’s chief said Friday.

Dr. Tedros Adhanom Ghebreyesus spoke after vaccinations began this week, with support from a U.N. peacekeeping mission, in Congo’s restive northeast where multiple rebel groups pose a threat and a heavily traveled border with Uganda is nearby.

Tedros and Congo’s health minister on Saturday planned to visit the village where the latest outbreak, Congo’s tenth, was declared on Aug. 1. The ministry says 48 cases have been reported, 21 of them confirmed as Ebola, including 11 deaths.

This outbreak is different from the one in Congo’s northwest that was declared over a week before this one began, Tedros said. “And that may require actually a stronger response.”

The use of the experimental vaccine and a swift international response were key in stopping the earlier outbreak, which killed 33 people. Health officials are using the same strategy now, first vaccinating health workers, contacts of Ebola cases and their contacts while finding and monitoring nearly 1,000 people so far.

“The vaccination alone cannot help,” Tedros warned, adding that finding and monitoring people is crucial, along with community awareness programs. WHO has said more than 3,000 doses of the Ebola vaccine are available in Congo.

The region’s shifting population poses a challenge. North Kivu province, where most of the cases in the new outbreak have been reported, hosts about 1 million internally displaced persons because of the regional insecurity, according to the U.N.’s migration agency.

The U.N. refugee agency on Friday said Ebola screenings are being carried out at transit points while an estimated 250 to 300 people a day cross into Uganda seeking refuge. Officials have said travel restrictions in response to the outbreak are not necessary.

Some worried Congolese have called for mass vaccinations in the border region, which the health minister said could not be done.

Others want more security.

“We call on the Congolese army to strengthen their presence and guard convoys of aid workers who are treating Ebola in the Beni region,” pastor Gilbert Kambale told The Associated Press.

Civil society groups have pointed out the threat from Allied Democratic Forces rebels who have killed more than 1,500 people in and around Beni in less than two years.