Neglected tropical diseases

WHO collaborates with the Association of Southeast Asian Nations to highlight the need for sustained dengue prevention and control

12 June 2013 | Geneva


The World Health Organization (WHO) joins the Association of Southeast Asian Nations (ASEAN) to observe ASEAN Dengue Day on 14 June 2013.

A series of activities are scheduled to promote enhanced awareness about dengue – an epidemic-prone viral disease – and also to educate children about the need for dengue prevention and control.

Every individual can contribute to prevent the spread of dengue by eliminating all sources of standing water, which are potential mosquito breeding sites in and around their own houses, in flower pots, gully traps, garden, discarded tyres, containers or roof gutters,” said Dr Raman Velayudhan of the WHO Department of Control of Neglected Tropical Diseases in Geneva, Switzerland. “We need to get every family member involved and help, as these simple activities make a big difference.

There is no vaccine or medicines against dengue and severe dengue. Preventing mosquitoes from breeding and propagating is the best method for containing its spread. Early detection of suspected cases, access to proper medical care and disease management can help in drastically lowering the rate of fatal cases.

WHO supports countries through its collaborating network of centres and laboratories, and provides technical support and guidance for the effective management of the disease. WHO published "Dengue guidelines for diagnosis, treatment, prevention and control" in 2009 and a "Global Strategy for dengue prevention and control, 2012–2020" in 2012.

Neglect to notoriety

Dengue is a neglected tropical disease that has become the fastest growing mosquito-borne disease, with almost half the world’s population now at risk. The disease is one of the leading causes of serious illness and death among children.

Prevention and control depend solely on effective and sustained vector control measures. There are four distinct, but closely related, serotypes of the virus that cause dengue (DEN-1, DEN-2, DEN-3 and DEN-4).

Recovery from infection by one provides lifelong immunity against that particular serotype. However, cross-immunity to the other serotypes after recovery is only partial and temporary. Subsequent infections by other serotypes increase the risk of developing severe dengue.

Global burden

The incidence of dengue has increased dramatically in recent decades. WHO currently estimates that 50–100 million dengue infections occur worldwide every year.

Before 1970, only nine countries had experienced severe dengue epidemics.

Today, the disease is endemic in more than 100 countries in WHO’s African, Americas, Eastern Mediterranean, South-East Asia and the Western Pacific regions. The Americas, South-East Asia and Western Pacific regions are the most seriously affected where more than 1.2 million cases were reported in 2008 and over 2.3 million in 2010 (based on official data submitted by Member States).

Recently, the number of reported cases has continued to increase and cases are being reported in several countries of WHO’s Africa and Europe Regions.

In 2010, 1.6 million cases of dengue were reported in WHO’s Region of the Americas alone, of which 49 000 cases were severe dengue.

Transmission and spread

The Aedes aegypti mosquito is the primary vector of dengue. The virus that causes dengue is transmitted to humans through the bites of infected female mosquitoes. Infected humans are the main carriers and reservoir of the virus, serving as a source of the virus for uninfected mosquitoes.

Ae. aegypti infests urban habitats and breed mostly in artificial containers.

Unlike other mosquitoes, Ae. aegypti is a daytime feeder, with peak biting periods early in the morning and in the evening before dusk.

Ae. albopictus, a secondary dengue vector in Asia, has spread to North America and Europe largely due to the international trade in used tyres (a breeding habitat) and other goods (e.g. lucky bamboo). Ae. albopictus is highly adaptive and can even survive in cooler temperate regions of Europe.

The spread of Ae. Albopictus is due to its tolerance to temperatures below freezing, hibernation, and ability to shelter in microhabitats.

The threat of a possible outbreak of dengue fever now exists in Europe. In 2010, local transmission of was reported for the first time in France and Croatia, and imported cases were detected in three other European countries.

An outbreak of dengue on Madeira Islands of Portugal in 2012 resulted in over 2000 cases and imported cases were detected in 10 other countries in Europe apart from mainland Portugal. An estimated 500 000 people with severe dengue require hospitalization each year, a large proportion of whom are children.

About 2.5% of those affected die.

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