The scientists analyzed more than 21 million calls to determine how often residents of Zanzibar travel and where they go. A semi-autonomous region composed of two islands off the coast of Tanzania in East Africa, Zanzibar has drastically reduced malaria in recent years. Its government commissioned the study as part of deliberations on whether to launch a total elimination campaign.
The calls indicated that most residents who leave the region make short trips to Dar es Salaam on the Tanzanian mainland nearby, where malaria is relatively uncommon. However, they also revealed that a few Zanzibar residents travel back and forth from more distant areas of Tanzania where the risk of getting the disease is much higher — posing the greatest threat to elimination.
“That group of the population is the real risk if Zanzibar wants to eliminate malaria,” said Andy Tatem, an assistant professor of geography, member of UF’s Emerging Pathogens Institute, and lead author of a paper on the research likely to appear in the January issue of the Malaria Journal. “That is the population group that is likely to be continually reintroducing infection.”
Malaria is not transmissible from person to person. But if infected elsewhere, travelers can be bitten by mosquitoes once back in Zanzibar — and those mosquitoes could then fly on to bite and infect other Zanzibar residents, forestalling elimination.
Over the past decade, Zanzibar’s aggressive campaign against malaria has reduced infections from as much as 40 percent of its 1.2 million people to less than 1 percent, Tatem said. The country is weighing the cost of a campaign to eliminate the disease against the cost of continuing indefinitely with the control measures now in place. Its government commissioned what Tatem described as Africa’s first “elimination feasibility study,” including the travel research.
Most Zanzibar residents journey to and from mainland Tanzania via four- to six-hour ferry trips, but records of their origin and destinations are poor, Tatem said. Inspired by recent cell phone-based epidemiological research in Europe, he and five colleagues obtained records of three months of calls from customers of the Zanzibar Telephone Company, which covers all of Zanzibar and Tanzania.
The October-December 2008 records, which contained no names or other identifying information, tracked the movements of a 770,369 customers by showing each customer’s calls and where the calls originated — or at least the region where the call originated.
So, for example, the researchers could see that a person made calls from Zanzibar’s main city of Stone Town Monday, Tuesday and Wednesday, but on Thursday and Friday from Dar es Salaam.
Most callers never left Zanzibar, which means they posed no threat of reintroducing the Malaria parasite, Tatem said. About 12 percent did leave the islands, but most of those only visited relatively safe Dar es Salaam, and usually for just one or two days at a time.
However, a few hundred residents made trips to regions of western and southern parts of Tanzania, where as many as 40 percent of the residents have the malaria parasite.
The cell records did not reveal any information about the threat from non-residents visiting Zanzibar. Many visitors to the historic center of the spice trade are likely to be tourists who either come from countries where malaria is not a problem or are taking anti-malarial drugs, so pose little threat for malaria importation. However, mainland residents visiting for work may carry infections, so future work will need to assess these risks too, Tatem said.
Tatem said the study gives Zanzibar’s government several options should it move forward with elimination. The government could choose to give Zanzibar residents prophylactics against malaria before they travel, or it could screen all residents as they return, both very expensive propositions. Or it could launch a targeted information and/or screening campaign aimed at the high-risk travelers.
Zanzibar will use the study in combination with another study — of the challenges and costs of eliminating the remaining infections within the country — to make its decision.
“Going for elimination can be very expensive, much more expensive than continuing with current sustained control, involving giving people bed nets (to protect against mosquito bites at night), spraying the inside of houses with insecticide and providing anti-malarial drugs,” he said. “But in the very long term the savings having no malaria may outweigh those costs.”
Andy Tatem | EurekAlert!
Smart Data Transformation – Surfing the Big Wave
02.12.2016 | Fraunhofer-Institut für Angewandte Informationstechnik FIT
Climate change could outpace EPA Lake Champlain protections
18.11.2016 | University of Vermont
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.
The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...
Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water
In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...
The efficiency of power electronic systems is not solely dependent on electrical efficiency but also on weight, for example, in mobile systems. When the weight of relevant components and devices in airplanes, for instance, is reduced, fuel savings can be achieved and correspondingly greenhouse gas emissions decreased. New materials and components based on gallium nitride (GaN) can help to reduce weight and increase the efficiency. With these new materials, power electronic switches can be operated at higher switching frequency, resulting in higher power density and lower material costs.
Researchers at the Fraunhofer Institute for Solar Energy Systems ISE together with partners have investigated how these materials can be used to make power...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
02.12.2016 | Medical Engineering
02.12.2016 | Agricultural and Forestry Science
02.12.2016 | Physics and Astronomy