Using old-fashioned detective work, public health workers in Mali, one of the world’s poorest nations, working with the Centers for Disease Control and Prevention and the World Health Organization, tracked and quarantined 108 people in two cities and a few roadside towns who may have had contact with a 2-year-old girl from Guinea who died of Ebola on Oct. 24.

There was even a car chase: The last bus the family traveled on during a 700-mile journey from Guinea was stopped on a rural highway, emptied out and disinfected.

A 21-day quarantine since the little girl’s death on Oct. 24 is almost over, and 41 of the 108 Malians in quarantine are due to be released Tuesday, and the remainder by Friday. Since none are showing symptoms, health officials are allowing themselves to hope that their quick response has kept Mali’s first outbreak to a single case.

If so, Mali will join Senegal and Nigeria in having proved yet again that rapid reactions can stop Ebola. In contrast, the initial outbreak in Guinea festered unaddressed for months before it exploded.