The global burden of dengue is thought to be substantial, but unrecognized and unreported infections, along with challenges around data access and quality, have made estimating its true burden difficult. Diverse sources have estimated the annual number of symptomatic dengue cases globally at anywhere between nine million and 100 million.
“Many countries have dengue surveillance systems that, while they provide very important information, don’t capture every case,” explains Donald Shepard, Professor at the Schneider Institutes for Health Policy at Brandeis University in Massachusetts. “And economic studies have looked at anywhere from 20 to 60 or 70 countries, while 141 around the world have dengue transmission.”
Infographic: The global cost of dengue
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Beyond solving technical problems
With the cost of dengue not well understood, dengue-endemic countries are struggling not only to track health progress and make decisions around health policy, but also to assess emerging preventative and control strategies.
Professor Shepard elaborates: “New dengue prevention and control technologies are becoming available. The first dengue vaccine has just been licensed in a few countries, for instance. That now leaves an important political and economic question: ‘How should these technologies be used to impact the disease?’.”
Answering that question will help countries decide which existing technologies they should adopt to help them fight dengue today, while guiding the continued development of promising new tools.
Extrapolating limited data on dengue
Professor Shepard was the primary author of a recent ‘cost of illness’ study into the global burden of dengue. Supported by Sanofi Pasteur, the study provides an objective, systematic and comparable measure of the global economic and disease burden of dengue.
Dengue in 2013:
58.40 million symptomatic dengue infections
13,586 fatal cases
Annual global costs of US$8.89 billion:
– 46.0% from non-fatal hospitalized cases
– 33.6% from non-fatal ambulatory cases
– 8.5% from non-medical cases
– 11.9% from fatal cases
The most comprehensive of its kind on dengue, the study was extensive. “Our team searched for and analysed relevant dengue articles published between 1995 and 2013 and systematically assembled and analysed the latest estimates from a wealth of diverse sources,” reveals Professor Shepard. “We also systematically reviewed published literature and responses to a survey of international experts.”
The study covers all 141 countries with active dengue transmission, despite a complete picture not being available for many of the countries. The team had to extrapolate systematically from the available information it had to build a complete picture.
Non-medical cases underestimated in the past
The study found that around 34 percent of global cases of dengue were non-medical cases: cases treated outside of the formal health sector. Previous studies have made the assumption that all symptomatic dengue cases got treatment in the formal healthcare sector. “Some people simply bear the fever at home; not every case consults with a medical professional,” says Professor Shepard.
Understanding the number of non-medical dengue cases is important. While they didn’t consume healthcare resources, they did still add to the economic burden of dengue. As Professor Shepard notes: “If children have dengue, for instance, then they cause an economic loss to their families because a parent would likely have to give up work to take care of them until they recover.”
Cutting the cost of dengue
The study provides both global and regional estimates on the cost of dengue, broken down by country and various short- and long-term costs. By putting a value on the size of the dengue problem, these estimates will help governments and donors make better-informed decisions around their dengue programmes.
“In most countries the public purse has more demands than it can satisfy,” says Professor Shepard. “Defining dengue in monetary terms means the disease can be compared with other economic problems. Public health systems can then leverage that information to secure resources from their Ministry of Finance – and possibly the donor community – to control the disease.”
More than that, the estimates allow the magnitude (and cost) of the dengue problem to be compared to the cost of trying to fix it. This cost/benefit analysis will encourage countries to allocate funds to their Ministry of Health to expand programmes to control the disease.
“Very often a society can substantially reduce its costs by endeavouring to fix the dengue problem rather than continuing to suffer the economic burden,” adds Professor Shepard.
A substantiated investment
Quantifying the burden of dengue will also encourage the use and development of new technologies. Professor Shepard uses the Philippines to illustrate how. Having licensed the vaccine at the end of 2015, the Philippines is the first country in the world to introduce the dengue vaccine in the public sector. It plans to vaccinate one million school children.
“Researchers in the Philippines, in collaboration with Brandeis, previously found that dengue cost their country $345 million in 2012 for healthcare alone, not counting lost productivity” he added. “This finding helped inform the country’s decision to commit US$73.5 million to its school-based vaccination programme.”
A conservative estimate
Despite quantifying the cost of dengue, Professor Shepard believes the study underestimates the true burden of dengue.
“The study didn’t put an economic value on the intangible: on the discomfort from having this illness or the anguish people feel when a loved one is ill or even dies,” elaborates Professor Shepard. “Additionally, other dengue burdens cannot be quantified yet. A country’s economy could be affected by loss of tourism by dengue, for example.” Both dengue and the Zika virus are causing great concern in Rio ahead of the forthcoming Olympic Games.
The professor suggests a number of approaches could improve future estimates, including merging multiple data sources (such as cohort and surveillance data), adjusting for unrecognized dengue cases and using modelling techniques to estimate dengue incidence in locations with limited data.
“Our hope is that a greater understanding of the main factors driving uncertainty around the burden of dengue will allow current estimates to be improved and, consequently, drive the evaluation of existing and potential future preventive and treatment approaches,” concludes Professor Shepard.
Learn more about the burden of dengue in our short-film.
Watch ‘The Lingering Effect of Dengue Fever’.