216 million people worldwide get infected with malaria. 655,000 people die from the disease. 90% of those deaths are in Africa. Malaria is spread via the bites of mosquitoes infected with a parasite and early symptoms are flu like and include fever, nausea, and aches. If left untreated it can be fatal. Since 2000, death rates have dropped by a 1/3 in Africa thanks to better prevention and control programs, but the region remains a hot spot.
Malaria is still a pressing issue for a lot of countries, particularly in Africa. That is what prompted Harvard researchers to track the spread of malaria in Kenya. However, not how you might expect. They used cell phone data (calls and messages) from 14.8 million cell phones. Using cell phone records from June 2008 through June 2009 they tracked the timing and origin of calls and texts, all users remained anonymous. Each call and text was fed through one of 11,920 cell towers in 692 Kenyan settlements. The individual’s location was then logged. People were ascribed a home area based on their most often used cell tower. Then each journey within the country could be tracked as cell phone users moved to different cell tower ranges. This built a picture of how they were traveling between towers on a weekly or monthly basis.
Using this data researchers created detailed maps of travel to and from malaria hot spots and made predictions about how human travel has affected the transmission of the disease. Human travel is an integral piece of the malaria puzzle. Mosquitoes fly approximately 1/2 a mile in their lifetime. People travel much further. Not only is it possible for mosquitoes to hitch rides in travelers belongings, but people themselves help the spread of the parasite. Aysmptomatic travelers could carry the parasite over a hundred miles. Now humans do not infect other humans directly. An infected human may arrive to a new area and be bitten by a malaria-free mosquito. The human infects that mosquito. The mosquito, now infected bites another person, and the cycle continues.
These findings help better understand how human travel patterns can spread disease and lead to improved public health efforts to curb the mosquito-borne infection. The disease travel map points out exact areas for concentrating malaria control efforts and suggests places where stopping malaria won’t have a big impact. Regional routes around Lake Victoria are major disease corridors for malaria. Towns along the routes are not spots for transmitting malaria to the rest of the country.
Researchers stated, “Mapping the routes of parasite dispersal by human carriers will allow for additional targeted control by identifying the regions where imported infections originate and where they may contribute substantially to transmission.” It is important to know where these hot spots are because with tight budgets it’s impossible to screen and treat everyone. Phones could be tools for targeting resources with practical applications.
With this information, governments could focus efforts on areas that were likely to both contribute and receive the highest number of infections. New control efforts could include boosting surveillance in these places, improving communication about the risk of travel to these areas, and perhaps sending text messages to travelers if they are visiting a high risk region. “As mobile phone data sets becomes increasingly available and representative of entire populations, we anticipate that studies like the one we present here will become common for understanding a range of different infectious diseases,” Buckee, et al.