A study being published today in the journal Science used millions of cell phone records to document the impact human movement has on malaria disease patterns in the fast-growing nation of Kenya.
The study, whose lead author is graduate student Amy Wesolowski of Carnegie Mellon University, also suggests new strategies for handling the malaria epidemic, a mosquito-borne disease that infects an estimated 216 million people worldwide and kills 655,000 a year, most of them children.
The part of Kenya with the highest malaria infection rate is the western edge around Lake Victoria. The study suggests the best plan for attacking the disease would be to concentrate on that area, because many of its residents carry the infection with them when they visit surrounding regions with a much lower disease rate.
In the past, governments and other organizations often have concentrated their malaria control efforts in low-infection regions, said Ms. Wesolowski, a Ph.D. student in CMU's Department of Engineering and Public Policy.
Those initiatives cost less and give people a sense of accomplishment, she said, but ultimately may be doomed to fail because those areas get so many travelers from high-infection areas.
Another potential benefit from the study might be to send text messages to people traveling from high-infection zones to other parts of the country, urging them to use bed nets at night, said Caroline Buckee, a professor at the Harvard School of Public Health and another author of the study.
It's important for people who are already infected with the malaria parasite to use bed nets, she said. If they don't, mosquitoes can bite them and spread the parasite to scores of other people.
The study tracked the cell phone records of nearly 15 million people over one year.
As expected, they found there was a lot of travel between outlying areas and the south central capital of Nairobi, which has 3 million residents.
But they were surprised by how much the entire population traveled from one region to the other, and particularly from the Lake Victoria area to districts around it.
David Zarembka, a Quaker peacemaking activist who lives in the Lake Victoria area, said much of that is related to Kenyan culture.
"Part of the culture of Kenya is keeping up with your family and neighbors," he said in an interview this week. "My wife was sick recently and all kinds of people came to visit her each day, including people from fairly far away."
The study, which also involved researchers from Johns Hopkins University in Baltimore, the University of Florida, the National Institutes of Health and the University of Oxford in England and Kenya, is part of a fast-growing trend known as mHealth, which uses mobile phones for research, diagnosis and treatment of diseases.
Amesh Adalja, a University of Pittsburgh infectious disease specialist not involved with the study, said other researchers are using the content of cell phone messages to track the outbreak of epidemics. There are experiments in using cell phones with special software to analyze blood samples and transmit the results to remote hospitals.
In Africa, there were 280 million mobile phone subscribers in 2008, Ms. Buckee said, and there will be an estimated 735 million users by the end of this year.
The the growth of cell phone use, she said, "is really incredibly rapid and is reaching all sectors of society."
Mark Roth: email@example.com or 412-263-1130.