Mosquito

Welcome to Denguematters - a dedicated newsletter and website covering the latest information, expert opinion, challenges and issues surrounding dengue - one of the fastest-emerging infections on the planet. More than 3.5 billion people, or over half the world’s population, across 120 countries live under the threat of dengue infection.

Given the scale of this threat, and the human and economic impact of dengue on families, communities and governments, it is remarkable that dengue remains poorly understood. Denguematters newsletter is designed to specifically address this educational need, encourage debate and increase awareness of this costly disease.

 

Issue 15 - Spotlight on Dengue In Southeast Asia

Dengue is a serious and growing public health problem in Southeast Asia. Outbreaks swept the region in 2013, and a growing body of evidence suggests that this infectious disease is under-recognized, underreported, and inadequately represented in estimates of disease burden and cost. Under-recognition of dengue’s impact in Southeast Asia could have deleterious effects, since accurate quantification is critical for policymakers who will set health priorities and make plans to implement disease control measures in 2014 based on disease burden. 
 

Economic and Health Burden

The most rigorous recent estimates place the annual economic burden of dengue at nearly $1 billion annually in the region. To arrive at this estimate, health policy researchers at Brandeis University, Waltham, Massachusetts, USA, analyzed World Health Organization (WHO) data, surveillance data, and published studies on Southeast Asia, then adjusted for underreporting.


Over the period of 2001-2010, researchers found in their study an annual average of 2.9 million cases and 5,906 deaths for the 12 countries analyzed (Bhutan, Brunei, Cambodia, East Timor, Indonesia, Laos, Malaysia, Myanmar, Philippines, Singapore, Thailand, and Viet Nam). The total annual cost estimate was $950 million, of which 52% resulted from lost productivity. 

The total disease burden was an estimated 214,000 disability-adjusted life years (DALYs), which works out to 372 DALYs for every 1 million individuals in the region; that rate is higher than 17 other conditions, including hepatitis B, upper respiratory infections, and Japanese encephalitis.

Perhaps the most valuable result from this rigorous analysis is estimates not only of aggregate disease and economic burden in Southeast Asia, but also country-specific estimates (see graphic). Because authors used a consistent methodology, comparisons between countries can be made. These estimates show a particularly high cost impact in Thailand ($290 million), Indonesia ($323 million), and Malaysia ($128 million), while disease burden was highest in Indonesia (95,168 DALYs) and the Philippines (37,685 DALYs).


 
The economic burden in this analysis would have been even higher, had the authors considered costs such as vector control and other prevention measures, which were excluded from the study. Even without counting those costs, the study demonstrates the compelling public health need for exploring new approaches to reducing dengue burden. 

 

Outbreaks Sweep Region

Some parts of Southeast Asia were hit particularly hard in 2013, as experts blamed above-average temperatures and an early rainy season. In many areas, mosquitoes were out in force in April, months in advance of what was expected in a typical season. Sharp increases in dengue incidence were seen in Singapore, Laos, and Thailand, while death rates climbed. 

In late August, health officials in Thailand reported 94 deaths, and nearly 100,000 cases, triple the rate reported for the same period a year earlier. Over that same period, officials in the Philippines reported 306 deaths. While the number of reported deaths in the Philippines was lower than those reported a year earlier, the rate of dengue-associated mortality is still the highest for the region. Singapore endured its harshest outbreak ever, with a record number of cases that sent the government scrambling to step up efforts to curb the outbreak. 

Reports of increased dengue activity in Southeast Asia continued throughout 2013. In October, the Ministry of Health in Malaysia reported an alarming jump in the number of dengue cases and deaths. A total of 21,453 cases were reported, representing an increase of approximately one-third over the comparable period from the previous year; likewise, the number of deaths rose sharply, up to 45 deaths, versus 27 deaths during the same period last year. Selangor state, which surrounds the capital city of Kuala Lumpur, was the hardest hit, reporting nearly half of the total cases (10,051). 


 

Control Efforts

Currently, officials in Southeast Asia can only rely on control measures and public-awareness campaigns to combat the outbreaks until a vaccine that will strengthen their disease intervention efforts becomes available in the future. In 2013, many Southeast Asian countries reported intensified efforts to contain the spread of the dengue-carrying mosquito, Aedes aegypti. In Bangkok, teams of municipal officers would fan out daily and fumigate communities to eradicate the mosquitoes and their breeding sites. 

In Malaysia, the Health Ministry checked 17,000 locations, levying monetary fines on those found to be harboring stale water pools containing mosquito larvae, and threatening imprisonment for repeat offenders. Meanwhile, workers checked construction sites and sprayed public places, including schools. 

Accurate disease incidence estimates are critical for guiding such public health decision making. However, many public health officials may be relying on estimates that under-recognize the true burden of disease because reporting is often based solely on clinical criteria. 

Tropical disease researchers have reported that in some Southeast Asian countries, national surveillance data substantially under-reported dengue cases. By analyzing data from prospectively followed cohorts with laboratory confirmation of dengue cases, the researchers found under-recognition of dengue cases by 8.7 fold in Thailand and 9.1 fold in Cambodia. With vaccine candidates currently under evaluation, more accurate incidence data will be critical not only for assessing economic impact and cost-effectiveness of a vaccination program, but also for policy makers to make decisions on the introduction of a new vaccine, according to the study authors. 


 

Changing Epidemiology

Throughout Southeast Asia, the epidemiology of dengue is changing with respect to age groups and population expansion beyond urban areas. For example, while dengue is generally considered to be a disease of early childhood (affecting individuals 2-15 years of age), increasing evidence exists that a shift to older age groups as well as infants as young as 1-2 months is occurring in endemic countries, including Thailand, Indonesia, and Singapore. 

Dengue has primarily been thought of as an urban public health problem because the disease-causing mosquito vector is so well adapted to human habitation. However, in recent years, dengue has spread into rural areas where, in the past, reporting of the disease was uncommon. This spread is occurring as rural living conditions become more similar to what is seen in urban areas; changes include different water storage and solid waste disposal practices, along with better connection between areas due to more modern transportation. 


 

Conclusion

In Southeast Asia, dengue is a significant public health problem that exacts a large health and economic burden. With the spread of dengue and changing demographics, prevention and control is more challenging than ever. In 2013, the region saw a series of outbreaks that included sharp increases in dengue-associated morbidity and mortality. Going forward, researchers note that the real impact and burden of dengue should be quantified and fully understood in order to facilitate well-informed decisions regarding policy priorities and strategies to control disease. 

 


References

Shepard DS, Undurraga EA, Halasa YA. Economic and disease burden of dengue in Southeast Asia. PLoS Negl Trop Dis. 2013;7(2):e2055.

 

Chaichalearmmongkol N. Dengue Fever Sweeps Southeast Asia. The Wall Street Journal, Aug. 16, 2013.

 

Gangopadhyay A. Dengue Deaths Rise in Malaysia. The Wall Street Journal. October 1, 2013.

 

Wichmann O, Yoon IK, Vong S, et al. Dengue in Thailand and Cambodia: an assessment of the degree of underrecognized disease burden based on reported cases. PLoS Negl Trop Dis. 2011 Mar 29;5(3):e996.

 

Bhatia R, Dash AP, Sunyoto T. Changing epidemiology of dengue in South-East Asia. WHO South-East Asia Journal of Public Health, January-March 2013:23-27.

 

Chareonsook O, Foy HM, Teeraratkul A, Silarug N. Changing epidemiology of dengue haemorrhagic fever in Thailand. Epidemiol Infect 1999;122:161-6.

 

Guha-Sapir D, Schimmer B. Dengue fever: new paradigms for a changing epidemiology. Emerg Themes Epidemiol. 2005 Mar 2;2(1):1.

 

Last edited: 16/04/2014