Conservationists say the dreaded Ebola virus along with decades of hunting and logging are putting some ape species on the brink of extinction in Central Africa.

Ebola, which kills through massive internal bleeding, has long been known to infect primates in Africa. It was first identified in 1976 and has since killed about 1,000 people, some of whom are believed to have contracted the disease by consuming or handling infected meat from wild animals.

Most at risk are western lowland gorillas and the Central African chimpanzee, both of which live in the dense rain forests of Central Africa, Conservation International said in a statement late Tuesday.

Christophe Boesch of the Wild Chimpanzee Foundation, who worked with Conservation International on a study, said Wednesday that Ebola was reported in May for the first time in Republic of Congo’s Odzala National Park, which contains the world’s largest concentration of western lowland gorillas.

“The fact that it has reached this important park is extremely worrying,” Boesch by telephone from Leipzig, Germany. “Ebola has been around the region, it’s not something new. But it’s worsening.”