Tanzania has confirmed a new case of Marburg virus disease in the northwestern Kagera region, following 25 negative tests. Dozens of individuals remain under observation as the government works to contain the outbreak.

Tanzania’s president says one sample from a remote northern part of the country has tested positive for Marburg disease.

A case of the bleeding virus Marburg has been confirmed in Tanzania, a week after authorities denied there was an outbreak. The deadly illness similar to Ebola is highly infectious, and can kill up to 88% of people without treatment.