Study estimates 390 million dengue cases a year in world, with India having highest burdenBMJ 2013; 346 doi: http://dx.doi.org/10.1136/bmj.f2339 (Published 12 April 2013) Cite this as: BMJ 2013;346:f2339
The annual number of cases of dengue worldwide is three times higher than the World Health Organization’s estimate, a new study indicates.
The multinational study, published in Nature,1 estimated that the number of infections stood at 390 million a year (95% confidence interval 284 million to 528 million), rather than the current WHO estimate of 50-100 million a year.2 It also showed that India had the highest burden of the disease, accounting for about a third of the world’s cases.
Dengue has seen a global resurgence recently despite extensive control efforts. Transmitted by Aedes aegypti, which unlike other mosquitoes bites during the day, the disease thrives in high density urban environments.
With the most advanced clinical trial for dengue vaccine by Sanofi Pasteur showing that the vaccine had an efficacy rate of only 30%,3 and no specific treatments in the pipeline, dengue continues to be a life threatening disease with substantial public health implications.
Of the 390 million total, only about one quarter of infections manifest clinically or subclinically, leaving most cases undetected.
The researchers used “well established risk mapping techniques with multicentre longitudinal cohort study data” to calculate the dengue burden, one of the authors, Oliver Brady, of Oxford University’s Department of Zoology, told the BMJ.
“The risk mapping techniques have been tried and tested in many scientific fields, and this latest study refines existing methods to address some of the issues inherent with mapping at global scales. The cohort study data we used are the most thorough measure of dengue infections in the community possible and are only obtainable by conducting multi-year observations in well established field sites,” Brady said.
Similar approaches have been used before to estimate the global burden of malaria, but this is the first time a systematic quantification and mapping of the worldwide burden of dengue fever has been done.
The study’s stratification of data by country also allows “comparison with national dengue reporting, after taking into account the probability of an apparent infection being formally reported,” the report says.
The study says that about 70% of the 96 million apparent infections occurred in Asia, with a third occurring in India. Brady added that “the high degree of urbanisation, rainfall, movement of people between cities, and the sheer number of people at risk are what makes India’s dengue burden stand out.”
A C Dhariwal, director of India’s National Vectorborne Disease Control Programme, told the BMJ that his department was striving to get a more accurate picture of the dengue problem by increasing the number of sentinel surveillance hospitals and laboratory facilities to boost diagnosis of the disease. In 2012 India had about 347 sentinel surveillance hospitals for dengue, up from 110 in 2007 and 170 in 2009.
“Early diagnosis and proper medical care based on national guidelines have brought down the case fatality to about 0.5%, though there has been a rising number of cases,” Dhariwal said.
Cite this as: BMJ 2013;346:f2339
bmj.com Feature: What can India do about dengue fever? (BMJ 2013;346:f643)