AsianScientist (Apr. 10, 2013) – Just last week, Asian Scientist reported that scientists believe estimates of the number of cases of dengue fever in South-East Asia and one country in South Asia are too low. Now, another team of researchers, publishing in the journal Nature, have found that the global burden of dengue infection is more than triple current estimates from the World Health Organization (WHO).
Dengue, also known as “breakbone fever” for the excruciating joint aches it can cause, is a viral infection transmitted between humans by Aedes mosquitoes. Infection can result in a wide spectrum of disease severity, ranging from mild fever to life-threatening illness. No antiviral drugs against dengue have been licensed, and the most advanced dengue vaccine candidate recently fell short of expectations in a much-anticipated clinical trial.
The global distribution of dengue infection risk and its public health burden have been poorly understood, although such information is essential for planning and implementing effective drug, vaccine, and vector control strategies. In the absence of better alternatives, WHO estimates of infection burden, intended as approximations, have been widely cited.
The study, led by Professor Simon Hay from the University of Oxford, used new disease modelling techniques to create a detailed, evidence-based, and up-to-date map of global dengue distribution, which allowed the authors to estimate infection numbers on a global, regional, and national scale.
The authors estimated that there are 96 million dengue infections worldwide each year that are severe enough to cause people to miss school or work. Asia, with its large swathes of densely populated urban areas that favor virus transmission, bore the brunt of the disease burden – 70 percent of these infections were predicted to occur in the region, with India alone accounting for one third of the global total.
In addition, the study estimated another 294 million annual mild or asymptomatic infections, suggesting the presence of a huge reservoir for the virus – a factor that will have significant implications for public health strategies aimed at disease control. The total number of 390 million annual dengue infections is more than triple the WHO’s most recent estimates of 50-100 million.
The study authors compiled and based their model on an exhaustive database of more than 8,300 records of dengue occurrences worldwide. The model also incorporated environmental and socioeconomic risk factors such as temperature, rainfall, and population density, as well as information gleaned from longitudinal dengue cohort studies.
“With globalization and the constant march of urbanization, we anticipate that there could be dramatic shifts in the distribution of the disease in the future: the virus may be introduced to areas that previously were not at risk, and those that are currently affected may experience increases in the number of infections,” said Prof. Hay. “We hope that the research will initiate a wider discussion about the significant global impact of this disease.”
Professor Jeremy Farrar, Director of the Wellcome Trust Vietnam Research Program and Oxford University Clinical Research Unit Hospital for Tropical Diseases in Vietnam, and an author on the study, explained the importance of the map and estimates:
“This is the first systematic robust estimate of the extent of dengue. The evidence that we’ve gathered here will help to maximize the value and cost-effectiveness of public health and clinical efforts, by indicating where limited resources can be targeted for maximum possible impact.”
The article can be found at: Bhatt et al. (2013) The global distribution and burden of dengue.
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Source: Wellcome Trust. Photo: Bindaas Madhavi/Flickr/CC.
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