Health officials say a second, more serious outbreak of Ebola in Mali started about two weeks ago, when a clinic made a mistake while treating a grand imam.

Doctors at the Pasteur Clinic in Bamako, Mali's capital, diagnosed the imam with kidney failure and never bothered to test him for Ebola—even after he died from the virus.

Immediately after the imam's death—and at a time when the virus is most contagious—dozens of people reportedly came into contact with his body.

"Because of his religious status as a Grand Imam, his body was transported to a mosque in Bamako for a ritual washing ceremony. The body was then returned to the native village of Kourémalé for formal funeral and burial ceremonies. Although these events are still under investigation, WHO staff assume that many mourners attended the ceremonies."

Since then, the imam's wife, daughter, and nurse have all died from "unexplained illnesses." His brother, his brother's wife, and their child are also reportedly being treated in an Ebola ward, as is a doctor who worked with the imam's nurse.

Authorities say the imam fell ill on Oct. 17 but wasn't diagnosed until Nov. 10, making it difficult to track the number of people who might have come into contact with him. Nearly 100 people have been quarantined so far.

Until this week, Mali had been on track to isolate its sole case of Ebola—a two-year-old Guinean girl who died Oct. 24.