Contrary to conventional thinking, the highest burden of dengue fever plagues rural areas rather than cities.
In a study led by Wolf-Peter Schmidt from the Nagasaki Institute of Tropical Medicine, Japan, the authors analysed a population in Kanh-Hoa Province in south-central Vietnam (350,000 people) that was affected by two dengue epidemics between January 2005 and June 2008.
They found that at low human population densities, mostly in rural areas, dengue risk is up to three times higher than in cities, presumably because the number of mosquitoes per individual is higher in low density areas.
The authors show that severe outbreaks of dengue occur almost exclusively in areas falling within a narrow range of human population densities with limited access to tap water, where water storage vessels provide breeding sites for the mosquitoes causing dengue fever.
However, as the actual number of people who contract dengue fever in populated areas is high, urban areas still substantially contribute to dengue epidemics.
The authors argue that improving water supply and vector control in areas with a human population density critical for dengue transmission could increase the efficiency of control efforts.
“Ideally, all people should have access to reliable tap water, not only to reduce the burden of dengue but also a range of other diseases associated with inadequate water supply such as diarrhea or trachoma, and to realize important economic benefits,” the authors said.
The study has been published in the journal PLoS Medicine.