Dengue fever – estimated 390 million infections each year
Dengue fever is a virus that is spread predominantly by the Aedes aegypti, a mosquito that also bites during the day and prefers to feed on humans. In recent decades, the disease has grown dramatically and is now a major international public health concern.
Dengue is found in tropical and sub-tropical regions around the world, predominantly in urban and semi-urban areas. The disease is now endemic in more than 100 countries in Africa, the Americas, the Eastern Mediterranean, South-East Asia and the Western Pacific. One estimate indicates that 390 million dengue infections occur each year. Illness from dengue fever can range from a severe flu-like illness to a potentially lethal haemorrhagic complication. Like malaria, it is a leading cause of hospitalization and death among children in seriously affected regions, especially in Asia and Latin America. There are four distinct, but closely related, viruses that cause dengue. Recovery from infection by one provides lifelong immunity against that virus, but confers only partial and transient protection against subsequent infection by the other three viruses.
Dengue fever is a severe, flu-like illness that affects infants, young children and adults, but seldom causes death. Symptoms vary according to the age of the patient and range from a fever with rash, mild fever or high fever, severe headache, pain behind the eyes, muscle and joint pains, and a rash.
Dengue haemorrhagic fever (DHF) is a potentially deadly complication that is characterized by high fever, often with enlargement of the liver, and in severe cases circulatory failure. The illness often begins with a sudden rise in temperature accompanied by facial flush and other flu-like symptoms. The fever usually continues for two to seven days and can be as high as 41°C, possibly with convulsions and other complications.
The dramatic spread of dengue is attributed to expanding geographic distribution of the four dengue viruses and their mosquito vectors. Infected humans are the main carriers of the virus, serving as a source of the virus for uninfected mosquitoes. A rapid rise in urban mosquito populations is bringing ever greater numbers of people into contact with this vector, especially in areas that are favorable for mosquito breeding, e.g. where household water storage is common and where solid waste disposal services are inadequate.
Aedes aegypti breeds primarily in man-made containers like earthenware jars, metal drums and concrete cisterns used for domestic water storage, as well as discarded plastic food containers, used automobile tires and other items that collect rainwater. In Africa, the mosquito also breeds extensively in natural habitats such as tree holes, and leaves that gather to form "cups" and catch water.
Controlling the spread of dengue is critical, as there is no vaccine to prevent it. Therefore, the challenge is to shift from trying to treat it, to trying to prevent its spread to humans. At present, the only method of controlling or preventing dengue virus transmission is to combat the vector mosquitoes. The application of appropriate insecticides to larval habitats, particularly those found in households, e.g. water storage vessels, prevents mosquito breeding for several weeks. Abate® larvicide, which is also approved for treatment of drinking water, is therefore an important tool for the control of the dengue virus.
Source: World Health Organization