ABUJA, Nigeria (AP) — The World Health Organization has declared the Ebola disease outbreak in Congo and Uganda a public health emergency of international concern.

Africa’s top public health body confirmed the outbreak in Congo’s Ituri province on Friday. By the following day, authorities said 336 suspected cases and 88 deaths had been reported. Congo’s health minister, Samuel Roger Kamba, said Tuesday that 134 people have died.

Health authorities say the outbreak is caused by Bundibugyo, a rare type of Ebola that has no approved medicines or vaccines. The outbreak is occurring in a part of Congo facing violent conflict with armed groups and a humanitarian crisis, complicating the response.

“This is a context that is incredibly complicated to try to manage,” said Lina Moses, an epidemiologist and disease ecologist at Tulane University who worked as a first responder coordinating contact tracing during the 2014 West Africa Ebola outbreak.

Here’s what to know:

How Ebola can spread
The Ebola virus is highly contagious and can be transmitted to people from wild animals. It spreads in the human population through contact with bodily fluids such as vomit, blood or semen, and with surfaces and materials such as bedding and clothing contaminated with these fluids.

The disease it causes is a rare but severe and often fatal illness in people. Symptoms include fever, vomiting, diarrhea, muscle pain and at times internal and external bleeding.

The virus was first discovered in 1976 near the Ebola River in what is now Congo. The first outbreaks occurred in remote villages in Central Africa, near tropical rainforests.

Read More: What to know about the outbreak of a rare kind of Ebola as cases and deaths rise