- by Malaria Consortium

Q&A: over two billion people at risk from dengue

A conversation with Malaria Consortium’s senior vector control specialist, Jeffrey Hii

A survey to measure dengue in Kandal province, Cambodia

A survey to measure knowledge, attitudes and practice surrounding dengue is carried out in Kandal province, Cambodia. Photograph: Malaria Consortium

Dengue is one of the fastest growing emerging infectious diseases in the world, with an estimated 50-100m cases of dengue every year – the vast majority in the Asia Pacific region. Malaria Consortium has been carrying out a number of projects in Asia to help reduce the burden of dengue. We spoke to Jeffrey Hii, the senior vector control specialist for Malaria Consortium in Asia, to find out more.

Can you describe what dengue is and how it differs from malaria?

Dengue fever and malaria are both mosquito-borne tropical diseases that are transmitted by the bites of infected mosquitoes. Dengue starts with a fever that lasts for about seven days and is accompanied by headaches and muscle or bone pain. Other symptoms of dengue include nausea, vomiting, painful eyes and rashes on the limbs. Malaria symptoms are similar but the fever tends to be of shorter duration compared to dengue.

The two diseases are diagnosed using different procedures. Malaria is detected by microscopy or antigen-based rapid diagnostic tests (RDTs) which can be used at a point of care and can give a result in 15-20 minutes. Dengue, however, is more difficult to diagnose meaning treatment can often be delayed. An RDT has recently been developed for dengue but the cost involved has deterred its widespread use. Unlike for malaria, there is no prescribed drug available for the treatment of dengue, so timely interventions can be crucial for saving lives. Treatment of acute dengue involves using oral or intravenous rehydration for moderate disease, and intravenous fluids and blood transfusions for severe cases.

No vaccines are available for malaria or dengue, although several are in clinical trials.

Why is it important to focus on dengue while diseases like malaria persist?  

The most recent assessment of the global prevalence of dengue identifies 128 countries with evidence of transmission and puts almost four billion people at risk.

Whilst the global burden of malaria is reported to be on the decline, Aedes mosquitoes – which transmit dengue – have expanded into warmer areas of high-income countries including Australia, the US, southern Europe, and Africa. In most tropical countries, dengue fever continues to exert a huge burden on populations, health systems and economies and is a significant threat to global public health. In 2010, all six World Health Organization (WHO) regions recorded dengue fever and indigenous outbreaks were reported for the first time in Europe. Given the enormity of the social and economic impacts of dengue, the international community needs to concentrate more efforts in controlling the disease.

Why is dengue considered to be a neglected disease?  

Dengue is among a group of neglected tropical diseases that has shown a significant increase in cases and geographical spread over the last 10 years, yet few globally coordinated efforts have been undertaken to address this increasing health threat. Effective implementation requires adequate staff with access to appropriate equipment, of which there is a marked shortage. This is in part due to both the neglect of capacity building on dengue prevention and to the attrition of staff to malaria programmes. A combination of reduced political will, insufficient financing to sustain intensive control efforts and the increasing decentralisation of national public health services is only serving to compound this lack of attention.

What are the best ways to address the rise in dengue cases? 

According to WHO, the alarming rise in dengue cases should be addressed using new tools for diagnosis and vector control, better case management, and focused research on suitable medicines and vaccines. An integrated vector management approach should reduce rates of morbidity by at least 25% and mortality by 50% by 2020. Aedes aegypti mosquitoes typically feed from humans indoors – it is therefore a public health imperative to control the mosquito in the home and in other indoor environments.

In order to make decisions about resource allocation, ministries of health and their partners need more epidemiological information than is currently available. Surveillance activities are limited due to diagnostic challenges and a lack of resources to collect relevant data. In part, this is due to the way dengue can be misdiagnosed because its symptoms are common to a host of other infectious diseases.

What is Malaria Consortium doing to prevent dengue from spreading further? 

Malaria Consortium has been working in Cambodia and Myanmar and has initiated activities in Thailand and Laos, to conduct comprehensive dengue surveillance assessments and to develop community participation and educational events on dengue. In areas such as these, where malaria and dengue are co-endemic, there is often intervention confusion between the two diseases at community level. Creating awareness of the symptoms of dengue and malaria is therefore very important, as is educating communities on the different habits of mosquitoes carrying dengue and malaria parasites. By working with community health workers, we have been identifying potential misconceptions that interfere with appropriate diagnosis and uptake of dengue interventions. This has included formally training health workers on how to respond to dengue outbreaks.

Malaria Consortium has also been focusing on the need for adequate environmental management and has been addressing basic water supply and solid waste disposal management services. We are committed to continue our support to achieve strengthened health systems in the community to limit the spread of vector-borne diseases.

 Content produced and managed by Malaria Consortium
 Originally published in The Guardian on 20 August 2014.