Study Roundup: Cell Phones May Help Prevent Infectious Disease Epidemics
Scientists use cell phone data to track the ways in which malaria and other infectious diseases spread.
The GistMalaria, an infectious and often fatal disease, is caused by several varieties of a parasite called Plasmodium. The disease is spread through bites from malaria-transmitting mosquitoes (Anopheles gambiae) which carry the parasite. Despite numerous and continuous efforts by the World Health Organization (WHO), the Bill and Melinda Gates Foundation, and many other health and charity institutions, the malady remains largely unconquered in the developing world. While malaria is mostly only widespread in sub-Saharan Africa, the WHO states that half the world population is at risk, and that Asia, Latin America, and some parts of the Middle East and Europe can be affected.
The WHO estimates that malaria kills one African child every minute. According to the 2011 World Malaria Report, there were 216 million malaria cases that year, which caused anywhere from 600,000 to 900,000 deaths. According to the Gates Foundation, the numbers are even higher: nearly 1,000,000 deaths a year, 85 percent of them children under five.
Adults can carry Plasmodium without actually getting sick. However, if bitten by mosquitoes, they can spread the disease geographically, especially when they travel. For this reason, it becomes difficult to control the outbreaks: even in the areas typically not affected, a transient carrier can cause an unexpected epidemic. As the developing world becomes increasingly better equipped with mobile technology, scientists have used the data obtained from a satellite provider in Kenya to track people traveling to and from infected areas. This data has helped scientists extrapolate how such movement may affect possible outbreaks.
The Expert TakePeople’s travel can contribute to the transmission of malaria in a much wider range than the limits of mosquito dispersal, found a recent study by Dr. Caroline Buckee of Harvard School of Public Health and her colleagues. Based on data from a Kenyan cellular service provider, Buckee and her team estimated the daily locations of almost 15 million people throughout the course of the year, during which mobile phone owners made wireless calls to nearly 12,000 cell towers. Buckee stated that the usage of mobile devices proved to be an excellent tool. In Kenya, a country of 40 million people, more than a third of its population carries a cell phone.
“Adoption of mobile phones in sub-Saharan Africa has been astonishing, much more rapid than in the Western world, so we knew it would be a powerful approach,” said Buckee in an interview with Healthline. The ability to accurately track down people’s travels was the key component to the study. Previous studies relied on the road network and weren’t as accurate, she said.
The scientists combined people’s travel data with a mathematical model of malaria transmission to estimate the probability of the disease being spread. For the purpose of the study, researchers identified two sources of importation of parasites. The first one consisted of individuals visiting endemic areas—they could contract the parasite on their journey and carry it back to their primary place of residence. The second category represented the already infected individuals who could carry parasites with them when they visited other settlements and potentially cause future infections.
“Traditional malaria control measures are focused on local prevention, on using mosquito nets and drugs,” said Buckee. “But new studies show that malaria is being imported and exported, and that dynamic happens on a larger scale than most local transmissions.”
The study showed that the outbreaks may not always happen in the areas where infected people live. Buckee noted that in the city centers there are few clinical cases of malaria, even if people who live there carry Plasmodium. There are significantly fewer mosquitoes in the urban areas, so even if a certain percentage of the population carries the parasite, the disease does not spread. However, if the infected urbanites travel to the countryside where mosquitoes are aplenty, they can cause an outbreak.
“You can pinpoint particular travel routes that are important for malaria prevention efforts,” Buckee said. “Targeting the area where infection originates is important.”
Source and MethodThe study researchers assigned every individual to their “primary settlement,” where they spent the majority of their time during the year. Based on the data from the cell phone provider, the researchers gathered the destinations and calculated the length of the people’s travels. Using the infection rates statistics from different geographical areas, they calculated the residents’ and the visitors' probability of being infected.
The TakeawayHuman movements can greatly influence the outbreaks of malaria, as well as other infectious diseases, such as influenza or the West Nile virus. In today’s mobile world, identifying how human travel affects the sources and locales of imported infections is extremely important for not only identifying the sources of infections, but also predicting where an epidemic may take place. Cellular technology and data may play a key role in preventing the next pandemic, Buckee pointed out.
“This study shows we can start using these technologies to get insights to a lot of epidemiological efforts,” she said. “This approach will be useful for many infectious diseases.”