New scientific insights into dengue vector ecology and disease transmission patterns, together with more targeted use of environmental management strategies, may offer improved potential for combating dengue fever, the world's fastest growing vector-borne disease.
Dengue fever, together with associated dengue haemorrhagic fever (DHF), is the most important vector-borne viral disease affecting humans. Aedes aegypti, the urban yellow fever mosquito, is also the principal dengue-carrying vector. A secondary vector is Aedes albopictus.
Aedes aegypti was eliminated from large areas of the Americas as part of the yellow fever mosquito eradication campaign in the 1950s and 1960s, but later reinvaded those areas. Dengue has emerged or re-emerged in Asia, the Americas and elsewhere over the past three decades, and presently occurs in nearly 100 tropical and subtropical countries (1). Epidemics have become progressively larger. In the year 2002, the disease was responsible for an estimated 19 000 deaths, as well as the loss of 616 000 disability-adjusted life years (DALYs) (2).
This disease surge is of particular concern since there is no curative treatment for dengue, and in many settings space spray applications of insecticides, or generalized community clean-up campaigns of vector breeding sites have had only a transient and limited effect, if at all, on disease incidence.
The resurgence of dengue
Social and environmental factors – including increased urbanization (particularly of poor populations lacking basic health services) as well as expansion of international travel and trade – are linked to the resurgence of dengue disease (3). Climate change also may affect transmission, as dengue mosquitoes reproduce more quickly and bite more frequently at higher temperatures (4, 5).
The epidemiology and ecology of dengue are complicated by the fact that there are four virus serotypes, some or all of which may be circulating in a particular endemic region at a particular time. Within any given local population, levels of immunity to each of the four serotypes may vary over time as a function of natural population growth, past population exposure to other serotypes, etc. Depending on the local level of immunity, therefore, an epidemic may erupt at higher or lower thresholds of vector density.
While beginning as a flu-like illness, dengue can develop into a deadly fever (dengue haemorrhagic fever). Unlike most other diseases, sequential infection with different serotypes increases – rather than reduces – the risk of severe illness. Most cases of dengue haemorrhagic fever occur in children under the age of 15.
The importance of good environmental management
In proximity to human settlements, Aedes aegypti mosquitoes breed primarily in artificial water containers, and the mosquito’s life-cycle is closely associated with human activities. Larval habitats are increasing rapidly in urban areas (1). Since there is no curative treatment for dengue, targeted environmental and ecosystem management is increasingly relevant. In many settings, however, generalized community clean-up campaigns or space-spray application of insecticides, have had only a transient and limited effect – or even no measurable effect at all – on disease incidence.
Answers & Comments
Answer:
New scientific insights into dengue vector ecology and disease transmission patterns, together with more targeted use of environmental management strategies, may offer improved potential for combating dengue fever, the world's fastest growing vector-borne disease.
Dengue fever, together with associated dengue haemorrhagic fever (DHF), is the most important vector-borne viral disease affecting humans. Aedes aegypti, the urban yellow fever mosquito, is also the principal dengue-carrying vector. A secondary vector is Aedes albopictus.
Aedes aegypti was eliminated from large areas of the Americas as part of the yellow fever mosquito eradication campaign in the 1950s and 1960s, but later reinvaded those areas. Dengue has emerged or re-emerged in Asia, the Americas and elsewhere over the past three decades, and presently occurs in nearly 100 tropical and subtropical countries (1). Epidemics have become progressively larger. In the year 2002, the disease was responsible for an estimated 19 000 deaths, as well as the loss of 616 000 disability-adjusted life years (DALYs) (2).
This disease surge is of particular concern since there is no curative treatment for dengue, and in many settings space spray applications of insecticides, or generalized community clean-up campaigns of vector breeding sites have had only a transient and limited effect, if at all, on disease incidence.
The resurgence of dengue
Social and environmental factors – including increased urbanization (particularly of poor populations lacking basic health services) as well as expansion of international travel and trade – are linked to the resurgence of dengue disease (3). Climate change also may affect transmission, as dengue mosquitoes reproduce more quickly and bite more frequently at higher temperatures (4, 5).
The epidemiology and ecology of dengue are complicated by the fact that there are four virus serotypes, some or all of which may be circulating in a particular endemic region at a particular time. Within any given local population, levels of immunity to each of the four serotypes may vary over time as a function of natural population growth, past population exposure to other serotypes, etc. Depending on the local level of immunity, therefore, an epidemic may erupt at higher or lower thresholds of vector density.
While beginning as a flu-like illness, dengue can develop into a deadly fever (dengue haemorrhagic fever). Unlike most other diseases, sequential infection with different serotypes increases – rather than reduces – the risk of severe illness. Most cases of dengue haemorrhagic fever occur in children under the age of 15.
The importance of good environmental management
In proximity to human settlements, Aedes aegypti mosquitoes breed primarily in artificial water containers, and the mosquito’s life-cycle is closely associated with human activities. Larval habitats are increasing rapidly in urban areas (1). Since there is no curative treatment for dengue, targeted environmental and ecosystem management is increasingly relevant. In many settings, however, generalized community clean-up campaigns or space-spray application of insecticides, have had only a transient and limited effect – or even no measurable effect at all – on disease incidence.