The species of Ebola virus causing an outbreak in Congo that has killed nearly 120 people is less common than other Ebola viruses, which is complicating the response because there are no specific treatments or vaccines.

Health officials say hundreds of suspected cases have been recorded in mining towns in eastern Congo’s Ituri province; tests point to the Bundibugyo strain, for which there is no…

The surge in cases marks the 17th Ebola outbreak in the Congo since 1976.