Tolima

Many of the yellow fever cases were clustered in the eastern part of Tolima province.

The team also explored places in Colombia that were previously closed to scientists, including Chaparral, a municipality in the Tolima region that was allowed to start welcoming tourists after the 2016 peace agreement.

Collaborating with three local universities -- University of La Salle, Universidad Distrital, and Universidad del Tolima -- the collective team traveled all across Colombia to collect more than 70 samples of bat species.

As part of the Escobar Lab's research staff, Alexander was able to study disease transmission in vampire bats and other local bat species, working with local communities in the Tolima region.

But some residents, including families who survived the devastating 1985 eruption by the Nevado del Ruiz, which straddles the border between Tolima and Caldas provinces, say they will not go.