Talking on cell phone

We often use our cell phones to locate restaurants or do some simple online banking while on the road. But a new study is using cell phone data to help curb the spread of malaria over vast areas of land.

A team of researchers combined cell phone data from 15 million people in Kenya with detailed information on the regional incidence of the disease. Scientists say the numbers reveal how human travel patterns contribute to malaria’s spread.

The study was conducted by researchers at Harvard School of Public Health (HSPH) and seven other institutions. It appears in the October 12, 2012 issue of the journal Science.

The team says that malaria, in large part, emanates from Kenya’s Lake Victoria region and spreads east – mainly toward the capital, Nairobi.

“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, in a news release.

Malaria is a potentially fatal blood disease. It is caused by a parasite that is transmitted to human and animal hosts by mosquitoes.

Malaria reportedly kills about 1 million people each year. Experts say 90% are children under age 5 in sub-Saharan Africa. It threatens more than 3 billion people globally. Until now, the disease has been fought with vaccines, mosquito nets and repellents.

Buckee went on to explain that tracking malaria goes beyond studying the location of the mosquitoes that carry the parasite. It is also essential to track the behaviour of the people who might be infected.

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Since many infected people have no symptoms, they can unintentionally carry the parasite during their travels and infect hundreds of others.

The amount of cell phone data used to calculate these movements is astounding.

Between June 2008 and June 2009, the team mapped every call or text made by each of the 14,816,521 Kenyan mobile phone subscribers to one of 11,920 cell towers located in 692 different settlements.

But every time an individual left his or her primary settlement, the destination and duration of each journey was calculated.

Then, using a 2009 malaria prevalence map provided by co-authors at the Kenya Medical Research Institute (KEMRI) and the Malaria Atlas Project to estimate the disease’s prevalence in each location being studied, the team inferred each resident’s probability of being infected and the daily probability that visitors to particular areas would become infected.

The researchers found that a surprisingly large fraction of “imported” infections end up in Nairobi, with infected residents returning there after journeys to spots such as Lake Victoria or the coast. Imported infections are those carried by people moving from one place to another.

The information available from these creative types of analyses could help public health officials decide where and how to control imported cases of malaria. For example, Buckee said, officials could send text message warnings to the phones of people traveling to high-risk areas, and suggest they use a bednet.

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