Congo’s health ministry told Reuters earlier this week that malaria was the culprit: “The mystery has finally been solved. It’s a case of severe malaria in the form of a respiratory illness,” it said Tuesday in a statement, according to Reuters. The ministry did not respond to multiple inquiries from NBC News.

A man in western Congo has died with hemorrhagic fever symptoms. Health authorities say that has led them to suspect that a still-unidentified virus may be involved alongside malaria in a mysterious outbreak that has killed dozens of people.

Malaria has been identified as the likeliest cause of an illness that has killed more than 80 people in south-western Democratic Republic of Congo, Africa's main health agency said. Victims of the previously unknown disease had been suffering flu-like symptoms such as fever, headaches, breathing difficulties and anaemia.