Buckee noted that the study doesn't involve finding someone with malaria and tracking their movements.
Rather, it uses the data that local officials have about malaria prevalence and population density and combines it with the location information from the phone companies. That's combined with mathematical models of malaria transmission. There's no information about individual people.
Skeeters Skirting Malaria Prevention
Aside for malaria, Buckee said there has been interest from other researchers in applying this method to studies of dengue, another mosquito-borne disease that tends to show up in tropical countries. Dengue, in fact, might be even easier to study as it tends to show up in urban areas where there are more cell phone towers, and thus better data on human movement.
Top image: Sources and sinks of people and parasites. The left map shows ranked sources (red) and sinks (blue) of human travel, while the right one shows the sources and sinks of parasites. The biggest source of parasites center on Lake Victoria, which is on the western side of the country, and the sink is in the area around Nairobi, in the south-central part of the map. Travelers, by contrast, move from Nairobi to Lake Victoria and back again.