Today, the World Health Organization releases its annual report on malaria. The disease kills some 600,000 people every year — most of them in Sub-Saharan Africa. Part of fighting any disease is understanding how populations move. And now, there’s a tech device now being used to tackle this challenge. It’s called… a cell phone.

An epidemiologist at Harvard named Caroline Buckee has been looking at massive amounts of cell phone data. Think the phone calls and texts of 15 million cell phone users in Kenya, for instance, with their locations triangulated by the phone company.

“So we combine that human mobility model with clinical information about the malaria parasite, and we use mathematical models to predict how people are going to spread it when they travel,” Buckee says. 

Think of plotting Malaria cases on a map and then overlaying data showing where people are moving, which helps make better predictions about where the disease might go next. Dr. Buckee points out that this data is thoroughly anonymous – they just see a bunch of dots. Still there are challenges.

“The challenges are the very poorest populations, and that the density of cell towers determines how high a resolution you can get your estimates,” Buckee says. “So, in some of the most rural and underserved populations, we have the hardest time.”

Buckee hopes those phones could someday warn people of an outbreak.