Dengue more prevalent in sparsely populated areas

Schmidt WP. PLoS Med. 2011;doi:10.1371/journal.pmed.1001082.

In areas with low human population densities, mostly in rural areas, dengue risk may be up to three times higher than in cities, according to a study published online.

Wolf-Peter Schmidt, MD, of the Nagasaki Institute of Tropical Medicine, Japan, and colleagues analyzed a population of about 75,000 households in Khanh Hoa province in south-central Vietnam, which was affected by two dengue epidemics between January 2005 and June 2008.

The researchers said 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.

“We identified a surprisingly narrow range of critical human population densities between around 3,000 to 7,000 people/km² prone to dengue outbreaks. In the study area, this population density was typical of villages and some peri-urban areas,” the researchers wrote.

However, as the actual number of people who contract dengue fever in populated areas is high, urban areas still substantially contribute to dengue epidemics, they said.

Schmidt and colleagues said in their study 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.

However, because supplying everyone with tap water is not a realistic short-term option in many low-income settings, reducing mosquito breeding around human settlements is an uphill struggle, the researchers said.

Disclosure: The researchers report no relevant financial disclosures.

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