Dengue is an important mosquito born viral infection that brings 250 million people, mostly living in the urban areas of countries like Pakistan, India, Pacific tropical and sub-tropical countries, under risk. It is estimated that more than 500 lac infections occur each year, including 500,000 hospitalizations for dengue hemorrhagic fever, mainly among children, with the case fatality rate exceeding 5% in some areas.
Dengue viruses belong to the genus flavivirus within the Flaviviridae family. DENV evolved in non-human primates from a common ancestor and each entered the urban cycle independently, an estimated 500–1,000 years ago. The mosquito vectors, principally Aedes aegypti, become infected when they feed on humans during the usual five-day period of viraemia. The virus passes from the mosquito’s intestinal tract to the salivary glands after an extrinsic incubation period, a process that takes approximately 10 days and is most rapid at high ambient temperatures. Mosquito bites after the extrinsic incubation period result in infection, which might be promoted by mosquito salivary proteins.
During initial dengue infections, most children experience a subclinical infection or mild undifferentiated febrile syndromes. During secondary dengue infections the pathophysiology of the disease changes dramatically, as infections can result in an acute vascular permeability syndrome known as dengue shock syndrome (DSS). The severity of DSS is age-dependent, with vascular leakage being most severe in young children, a phenomenon that is thought to be related to the intrinsic integrity of the capillaries.
Dengue-associated deaths are usually linked to Dengue Hemorrhagic Fever/Dengue Shock Syndrome. Even though vaccines or drugs aren’t available for treatment, the severe disease can be successfully managed by careful monitoring of warning signs and early initiation of aggressive intravenous rehydration therapy. Early resuscitation can prevent other complications, such as massive hemorrhage, disseminated intravascular coagulation, multiple organ failure, and respiratory failure due to non-cardiogenic pulmonary edema.
To reduce or prevent dengue virus transmission there is currently no alternative to vector control. Most endemic countries have a vector control component in their dengue control and prevention programmes but its delivery by public health practitioners is frequently insufficient, ineffective or both.
Dengue viruses belong to the genus flavivirus within the Flaviviridae family. DENV evolved in non-human primates from a common ancestor and each entered the urban cycle independently, an estimated 500–1,000 years ago. The mosquito vectors, principally Aedes aegypti, become infected when they feed on humans during the usual five-day period of viraemia. The virus passes from the mosquito’s intestinal tract to the salivary glands after an extrinsic incubation period, a process that takes approximately 10 days and is most rapid at high ambient temperatures. Mosquito bites after the extrinsic incubation period result in infection, which might be promoted by mosquito salivary proteins.
During initial dengue infections, most children experience a subclinical infection or mild undifferentiated febrile syndromes. During secondary dengue infections the pathophysiology of the disease changes dramatically, as infections can result in an acute vascular permeability syndrome known as dengue shock syndrome (DSS). The severity of DSS is age-dependent, with vascular leakage being most severe in young children, a phenomenon that is thought to be related to the intrinsic integrity of the capillaries.
Dengue-associated deaths are usually linked to Dengue Hemorrhagic Fever/Dengue Shock Syndrome. Even though vaccines or drugs aren’t available for treatment, the severe disease can be successfully managed by careful monitoring of warning signs and early initiation of aggressive intravenous rehydration therapy. Early resuscitation can prevent other complications, such as massive hemorrhage, disseminated intravascular coagulation, multiple organ failure, and respiratory failure due to non-cardiogenic pulmonary edema.
To reduce or prevent dengue virus transmission there is currently no alternative to vector control. Most endemic countries have a vector control component in their dengue control and prevention programmes but its delivery by public health practitioners is frequently insufficient, ineffective or both.
Given its behaviour and generally close association with humans, the principal vector A. aegypti requires the use of a combination of vector-control methods, notably environmental management methods and chemical control methods based on the application of larvicides and adulticide space sprays. Chemical controls typically must be added to water stored for domestic use, including drinking water.
Environmental management is generally considered to be an essential component of dengue prevention and control, particularly when targeting the most productive container habitats of the vector. Source reduction, ‘clean-up’ campaigns, regular container emptying, cleaning (targeting not only households but also public spaces such as cemeteries, green areas and schools,) installation of water supply systems, solid waste management and urban planning, all fall under the rubric of environmental management.
However, huge investments in infrastructure are needed to increase access to safe and reliable water supplies and solid waste disposal systems.
Most efforts in vector control are centered at the household and community levels, but with few exceptions, the achievements to date have been largely unspectacular and there have been difficulties in scaling up from the project level. Nevertheless, such community-based interventions are widely seen as the most promising way of improving delivery and achieving long-term control of the vector through behavior.
Most efforts in vector control are centered at the household and community levels, but with few exceptions, the achievements to date have been largely unspectacular and there have been difficulties in scaling up from the project level. Nevertheless, such community-based interventions are widely seen as the most promising way of improving delivery and achieving long-term control of the vector through behavior.
Dengue is now a global threat and is endemic or epidemic in almost every country located in the tropics. While we wait for new tools such as vaccines, antiviral drugs and improved diagnostics, better use should be made of the interventions that are currently available. The challenge that awaits us in the near future will be how to scale up to deploy these new tools.
In recent years, several partnerships such as the PDVI, the Innovative Vector Control Consortium, the Asia-Pacific Dengue Prevention Partnership and the European Union’s DENFRAME and DENCO projects have come into existence, receiving funding from the Bill and Melinda Gates Foundation, regional Development Banks and the private sector. These partnerships are working with WHO and national governments to develop new tools and strategies to improve diagnostics and clinical treatments and to achieve a successful vaccine.
In recent years, several partnerships such as the PDVI, the Innovative Vector Control Consortium, the Asia-Pacific Dengue Prevention Partnership and the European Union’s DENFRAME and DENCO projects have come into existence, receiving funding from the Bill and Melinda Gates Foundation, regional Development Banks and the private sector. These partnerships are working with WHO and national governments to develop new tools and strategies to improve diagnostics and clinical treatments and to achieve a successful vaccine.
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