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WHO scales up response to worldwide surge in dengue

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Aedes aegypti; adult female mosquito taking a blood meal on human skin. © WHO/TDR /Sinclair Stammers

Over the past several months, Pakistan hospitals have faced an influx of thousands of patients admitted with headache, muscle pain and high fever, all classic symptoms of dengue, a mosquito-borne virus that has struck large numbers of people across the country. Pakistan health officials say they are battling one of the worst dengue outbreaks the country has experienced. One city hospital in Rawalpindi admitted more than 2000 dengue patients in a single weekend in October, straining emergency services, converting ordinary wards into dengue wards, and forcing staff to work overtime.

As of early November, more than 45 000 people in Pakistan have been infected with the dengue virus in 2019.

Pakistan is not the only country confronting a surge in dengue cases this year. Bangladesh also has been in the grip of its worst dengue outbreak since the country first recorded an epidemic in 2000, with more than 92 000 cases reported. Health officials in the region blame the prolonged monsoon rains, which promote ideal breeding grounds for Aedes mosquitoes that carry the dengue virus and thrive in warm, humid conditions, laying their eggs in used tires, flowerpots, tree holes and any water-filled container.

Numerous other countries in Asia, the Americas and Africa are reporting a higher incidence of dengue than previous years. WHO is working with local health officials to strengthen dengue outbreak alert systems and improve vector control strategies to halt the spread of the virus.

“The rise in outbreaks this year is a wake-up call for governments, policymakers and researchers to strengthen surveillance and control programmes and to step up prevention strategies to control this phenomenal spread of dengue and other vector-borne viruses,” says Dr Raman Velayudhan, coordinator of WHO’s vector management programme in Geneva.

Outbreaks increasing worldwide

The frequency of dengue outbreaks has grown dramatically around the world in recent decades and is currently the fastest spreading mosquito-borne viral disease in the world. Known to exist in only 9 countries in the 1970s, dengue is now endemic in 128 countries and strikes as many as 96 million people each year, according to global data collected by WHO.

The unprecedented surge in dengue epidemics across the globe in recent decades prompted WHO at the start of 2019 to include the virus in its list of the world’s top 10 public health threats.

WHO is working with governments and health partners to scale up the global response to the escalation of dengue outbreaks through national vector control programmes aligned with WHO’s Global vector control response strategy. The strategy aims to strengthen vector control worldwide through heightened surveillance and monitoring of Aedes mosquitoes and other mosquito-borne viruses. It also aims to reinforce laboratories and community interventions to prepare for and respond swiftly to outbreaks of mosquito-borne viruses.

“We need to further engage communities to push for more proactive, sustainable preventive measures rather than simply reacting to outbreaks,” says Dr Velayudhan.

Engaging local communities

In Pakistan, the health ministry has launched an extensive community awareness campaign targeting more than 28 800 households in the twin cities of Rawalpindi and Islamabad, where dengue cases are most concentrated. The campaign has set up mobile medical camps in various neighbourhoods, distributed mosquito nets and insect repellents to residents, and provided free clinical services to more than 20 000 dengue patients. The government has set up a special task force to lead response activities across the country, with the support of the National Institute of Health, which is providing technical assistance and laboratory services to ascertain the dengue virus serotypes circulating in the various geographical zones.

The WHO office in Pakistan has donated anti-mosquito fogging equipment, along with thousands of flyers, posters, banners and brochures distributed in schools, railway stations and other public places to provide information to explain the dengue virus and its symptoms. The campaign messages provide contact information for medical assistance at the onset of dengue symptoms and highlight ways to prevent mosquitoes from breeding – such as by emptying any containers storing water, where mosquitoes like to breed – and avoiding mosquito bites through proper clothing and use of mosquito repellent and bed nets.

The dengue virus is transmitted to humans by two species of mosquito, the Aedes aegypti and Aedes albopictus, mosquitoes that also transmit yellow fever, Zika, chikungunya and other viruses. The dengue virus causes flu-like illness and can develop into a potentially fatal severe dengue. There is no specific treatment for dengue, but early detection and access to proper medical care can prevent severe cases from becoming fatal.

Tackling dengue through regional and global action

WHO country offices are working in all regions of the world to strengthen vector control measures to control the spread of dengue and other mosquito-borne diseases. In the Americas, the Pan American Health Organization is assisting communities to eliminate mosquito breeding sites around homes and public spaces and supporting training programmes for health professionals to improve dengue diagnosis and treatment.

WHO’s Western Pacific Regional Office is taking a similar approach, training health professionals and preparing clinics and hospitals to respond more effectively to the influx of patients during an outbreak.

In the Africa region, WHO is providing technical and financial support in all aspects of dengue response and vector control, including surveillance, lab testing, coordination and community engagement, which WHO is leading in response to current outbreaks in Benin, Cote d’Ivoire, Senegal and Tanzania.

Previously confined to the tropics, Aedes mosquitoes in recent years have begun crossing into more temperate zones. Countries such as Nepal are beginning to report cases of dengue, chikungunya and Zika, as climate change expands the range of the Aedes habitat into cooler, higher elevations. The changing geographic distribution of mosquito-borne diseases is increasingly a cause of concern also in Europe. Since 2010, dengue cases have been recorded in France, Italy, Portugal and Spain.

“As the global climate warms, we are sure to see Aedes mosquitoes extending their reach farther into territories previously untouched by dengue and other arboviruses,” says Dr. Velayudhan. “Climate action must include coordinated international efforts to ensure countries are prepared to respond effectively to the global challenge of battling dengue and other diseases that will escalate in an increasingly warmer world.”

Concerted action by individuals, communities and countries will be critical to reduce the scale, frequency, and impact of dengue outbreaks, as WHO continues to mobilize governments and health partners to implement stronger, smarter strategies to combat the expanding footprint of the Aedes mosquitoes and the diseases they spread.