What do you get when you combine cell phone data from 15 million people in Kenya with detailed information on the regional incidence of malaria? Answer: new research that reveals how human travel patterns are contributing to the spread of malaria, according to researchers from the Harvard School of Public Health (HSPH).
The findings of the study, which appear in the Oct. 12 issue of the journal Science, indicate that malaria emanates from Kenya's Lake Victoria region and spreads east, chiefly toward the capital, Nairobi. The article's authors argue that human movements contribute to the transmission of malaria on spatial scales that exceed the limits of mosquito dispersal.
HSPH researchers believe identifying the sources and "sinks" (areas that mostly receive disease) of imported infections due to human travel and locating high-risk sites of parasite importation could greatly improve malaria control programs. Malaria kills about 1 million people each year--90 percent are children under age 5 in sub-Saharan Africa--and threatens over 3 billion globally.
"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," senior author Caroline Buckee, an assistant professor of epidemiology at HSPH, said in a statement.
Researchers mapped calls and texts made by nearly 15 million Kenyan mobile phone subscribers to one of almost 12,000 cell towers located in 692 different settlements. Every time an individual left his or her primary settlement, the destination and duration of each journey was calculated. Using a malaria prevalence map provided by co-authors at the Kenya Medical Research Institute and the Malaria Atlas Project, researchers inferred each resident's probability of being infected and the daily probability that visitors of particular areas would become infected.
Researchers found that a surprisingly large fraction of "imported" infections--that is, infections that are carried by people moving from one place to another--wind up in Nairobi, with infected residents returning there after journeys to spots such as Lake Victoria or the coast.
Researchers at St. George's, University of London and U.K. last month announced plans to build a mobile device that uses nanotechnology to diagnose and treat drug-resistant malaria.