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Human movement plays critical role in disease transmission


The study presents the work of an international, multidisciplinary team of vector biologists, sociologists and virologists studying dengue in Iquitos, Peru.

Understanding the behavior of the people and mosquitoes can lead to better surveillance, intervention and improved prevention of diseases like dengue, said Stoddard, a postdoctoral scholar in the laboratory of Professor Thomas Scott of the UC Davis Department of Entomology. Dengue appeared in Iquitos in 1990, and since then its incidence rate has varied from approximately 5 percent to more than 30 percent after new virus serotype introductions, Stoddard said.

No vaccine or cure is currently available for dengue, which is transmitted by the tiger-striped, day-biting mosquito Aedes aegypti. Some 2.5 billion to 3 billion people are at risk for dengue each year, and 50 million to 100 million suffer from clinically apparent dengue, according to Scott.

To track individual human movement, the research team uses small GPS devices and culturally sensitive interviews that were developed by the team.

"We do not necessarily expect to be able to identify actual places or individuals where the risk is greatest because the population dynamics of the vector and the behavior of the hosts are too transient," Stoddard said. "We do hope, however, to arrive at a much better understanding of the mechanics of transmission - like why epidemics occur even when vector abundances are low - and of the types of places and types of individuals at greatest risk."

The researchers developed a conceptual model showing that the relevance of human movement at a particular scale depends on mosquito behavior. Focusing on Aedes aegypti, they illustrated how biting behavior combined with fine-scale movements of individual humans engaged in daily routines can influence disease transmission. They also outlined several considerations for designing epidemiological studies to encourage studies of individual human movement.

"We hope to arrive at a better notion of the spatial scale on which dengue transmission occurs and from an operational standpoint, at what scale to focus interventions," Stoddard said. Another aim is to encourage researchers of other mosquito-borne diseases, such as malaria, "to conduct more incisive examinations of individual human movements."