Dengue – Basic Facts for Public Education

Dengue is the most widespread mosquito-borne infection in human beings, which in recent years has become a major international public health concern. It is usually found in tropical and sub-tropical regions around the world, particularly in urban and semi-urban areas. Over the last 15 years, we have witnessed a dramatic increase in the global incidence of dengue and its severe manifestations such as dengue hemorrhagic fever (DHF) and dengue shock syndrome (DSS). Almost 95% of Dengue cases are amongst children under the age of 15 years. Without proper management, Dengue Hemorrhagic Fever case fatality rates can exceed 20%, however, with modern intensive supportive therapy these rates can be reduced to less than 1%.

Transmission

Dengue viruses are transmitted to humans through the bite(s) of infective female Aedes Aegypti mosquitoes, which generally acquire the virus while feeding on the blood of an infected person. After incubation for 8-10 days, an infected mosquito is capable, during probing and blood feeding, of transmitting the virus, to susceptible individuals for the rest of its life. Infected female mosquitoes may also transmit the virus to their offspring by transovarial (via the eggs) transmission.

Humans are the main amplifying host of the virus, although studies have shown that in some parts of the world monkeys may become infected and perhaps serve as a source of virus for uninfected mosquitoes. The virus circulates in the blood of infected humans for 2-7 days, at approximately the same time as they have fever Aedes Aegypti mosquitoes may acquire the virus when they feed on an individual during this period.

Prevention and control measures

Presently, the only method of controlling or preventing DF and DHF is to combat the vector mosquitoes. 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 tyres and other items that collect rainwater.

Vector control is implemented using environmental management and chemical methods. Proper solid waste disposal and improved water storage practices, including covering containers to prevent access by egg laying female mosquitoes, are encouraged through community-based programmes.

The application of appropriate insecticides to larval habitats, particularly those used by the households, such as water storage vessels can prevent mosquito breeding for several weeks therefore these insecticides must be used periodically. The use of family size insecticide treated nets (ITNs) is also recommended. General insecticide spraying targeting mosquito breeding habitats need to be carried out to kill adult mosquitoes using portable or truck-mounted machines.

Guidelines for the families of affected persons

Keep body temperature below 39oC. Give the patient paracetamol (not more than four times in 24 hours) according to the dose prescribed below:

Age
Dose (tablet 250 mg)
Mg/dose

< 1 year
¼ tablet
60

1-4 years
½ tablet
60-120

5 and above
1 tablet
240

  • Do not give the patient Aspirin or Ibuprofen
  • Give large amounts of fluids (water, soups, milk and juices) along with the patient’s normal diet
  • The patient should rest
  • Immediately consult your physician if any of the following manifestations appear: Red spots or points on the skin; bleeding from the nose or gums; frequent vomiting; vomiting with blood; black stools; sleepiness; constant crying; abdominal pain; excessive thirst (dry mouth); pale, cold or clammy skin; or difficulty in breathing.

Characteristics

Dengue fever is a severe, flu-like illness that affects infants, young children and adults, but seldom causes death. The clinical features of dengue fever vary according to the age of the patient. Infants and young children may have a non-specific febrile illness with rash. Older children and adults may have either a mild febrile syndrome or the classical incapacitating disease with abrupt onset and high fever, severe headache, pain behind the eyes, muscle and joint pains, and rash.

Dengue hemorrhagic fever is a potentially deadly complication that is characterized by high fever, hemorrhagic phenomena, often with enlargement of the liver and in severe cases, circulatory failure. The illness commonly begins with a sudden rise in temperature accompanied by facial flush and other non-specific constitutional symptoms of dengue fever. The fever usually continues for two to seven days and can be as high as 40-41°C, possibly with febrile convulsions and hemorrhagic phenomena.

In moderate DHF cases, all signs and symptoms abate after the fever subsides. In severe cases, the patient’s condition may suddenly deteriorate after a few days of fever when the temperature drops, followed by signs of circulatory failure, and the patient may rapidly go into a critical state of shock and die within 12-24 hours, or quickly recover following appropriate volume replacement therapy.

Immunization

At the present time, no vaccination is available against Dengue Fever or Dengue Hemorrhagic Fever.

Prevent mosquito bites

  • Dengue mosquitoes bite during the daytime – protect yourself from the bite
  • Wear full-sleeve clothes and long dresses to cover the limbs.
  • Use repellents–care should be taken in using repellents on very young children or the elderly
  • Use mosquito coils and electric vapour mats during the daytime to prevent mosquito bites
  • Use insecticide treated nets (ITNs) to protect young children, pregnant women, old people, in addition to others who may rest during the day.
  • Curtains (cloth or bamboo) can also be treated with insecticide and hung at windows or doorways, to repel or kill mosquitoes.

Prevent multiplication of mosquitoes (Vector Control)

Mosquitoes which spread Dengue live and breed in stagnant water in and around houses, and places where solid waste is dumped.

  • Drain out the water from desert/window air coolers when not in use, in addition to tanks, barrels, drums, and buckets.
  • Remove all objects containing water such as plant saucers from the house.
  • All stored water containers should be kept covered at all times.
  • Collect and destroy discarded containers in which water collects, such as bottles, plastic bags, tins, tyres, etc.
  • Efficient disposal of all solid waste/garbage.

Basic facts about Dengue and Dengue Hemorrhagic Fever

How does dengue spread? Dengue is spread through the bite of an infected Aedes Aegyptimosquito. The mosquito gets the virus by biting an infected person. The first symptoms of the disease occur about 5-7 days after the infected bite. There is no way to tell if a mosquito is carrying the Dengue virus. Therefore, people must protect themselves from all mosquito bites.

Where does this mosquito live? This mosquito rests indoors, in closets and other dark places. Outside, it rests where it is cool and shaded. The female mosquito lays her eggs in water containers in and around homes, schools and other areas in towns or villages. These eggs become adults in about 10 days.

Where does the mosquito breed? Dengue mosquitoes breed in stored, exposed, water collection systems. The favoured breeding places are: barrels, drums, jars, pots, buckets, flower vases, plant saucers, tanks, discarded bottles/tins, tyres, or water coolers, and other places where rainwater collects or is stored.

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