New research that combines cell phone data from 15 million people in Kenya with detailed information on the regional incidence of malaria has revealed, on the largest scale so far, how human travel patterns contribute to the disease’s spread. The findings from researchers at Harvard School of Public Health (HSPH) and seven other institutions indicate that malaria, in large part, emanates from Kenya’s Lake Victoria region and spreads east, chiefly toward the capital, Nairobi.

The study appears in the October 12, 2012 issue of the journal Science.

“This is the first time that such a massive amount of cell phone data—from millions of individuals over the course of a year—has been used, together with detailed infectious disease data, to measure human mobility and understand how a disease is spreading,” said senior author Caroline Buckee, HSPH assistant professor of epidemiology.

Malaria kills about 1 million people each year—90% are children under age 5 in sub-Saharan Africa—and threatens over 3 billion globally.

To estimate malaria’s potential spread, it’s important to factor in not only information about the location of the mosquitoes that carry the malaria parasite, but also the behavior of the people who might be infected, said Buckee. Since many infected people have no symptoms, they can unintentionally carry the parasite during their travels and infect hundreds of others.