Tanzania’s president said Monday that one sample from a remote part of northern Tanzania tested positive for Marburg disease, a highly infectious virus which can be fatal in up to 88% of cases without treatment.

President Samia Suluhu spoke in Dar es Salaam, the commercial capital, alongside World Health Organization chief Tedros Adhanom Ghebreyesus.

WHO was the first to report on Jan. 14 of a suspected outbreak of Marburg that had killed eight people in Tanzania’s Kagera region. Tanzanian health officials disputed the report hours later, saying tests on samples had returned negative results.

Suluhu said Monday that further tests had confirmed a case of Marburg. Twenty-five other samples were negative, she said.

Like Ebola, the Marburg virus originates in fruit bats and spreads between people through close contact with the bodily fluids of infected individuals or with surfaces, such as contaminated bed sheets.

Symptoms include fever, muscle pains, diarrhea, vomiting and in some cases death from extreme blood loss. There is no authorized vaccine or treatment for Marburg.