In a publication of this week’s PLoS Medicine, researchers report that in dengue-endemic areas such as South-East Asia, contrary to previous beliefs, those living in rural areas have a higher risk of becoming infected with dengue fever than those living in cities. Dengue fever is a viral infection causing sudden high fever, severe headache as well as muscle and joint pains that can develop into a life-threatening condition called dengue hemorrhagic fever.

Wolf-Peter Schmidt from the Nagasaki Institute of Tropical Medicine in Japan led a study in which they analyzed a population of approximately 350,000 people in Kanh-Hoa Province (South-central Vietnam) that suffered two dengue epidemics between January 2005 and June 2008.

Their discovery showed that areas with low human density, i.e. rural areas, had a three times higher risk of dengue fever compared to cities, presuming that the reason is larger amounts of mosquitoes per individual in rural areas compared to those in cities.

According to the authors, severe dengue outbreaks occur almost exclusively in areas with sparsely populated densities that have limited access to tap water and therefore use water storage vessels, which provide breeding grounds for the dengue-transmitting mosquitoes.

Urban areas are a large contributor to dengue epidemics as the actual number of dengue-infected people in populated areas is high.

They urge health authorities to make control efforts more efficient with improved water supplies and vector control in areas with a human population density critical for dengue transmission, writing that:

“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.”

For many low-income areas tap water supply is not a realistic short-term option and reducing mosquito breeding around human settlements is an ongoing battle.

In a concluding statement, the authors write:

“Additional intervention measures in areas with a human population density critical for dengue virus transmission could increase the efficiency of vector control, especially since population density figures are relatively easy to obtain.”

Written by Petra Rattue