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What is dengue?

Dengue is a flu like illness caused by any of four closely related antigenically different dengue viruses (DEN 1, DEN 2, DEN 3 or DEN 4). The virus is transmitted to humans by the bite of an infected female mosquito. The incubation period of dengue fever normally ranges from between 3 to 14 days. Many patients infected with dengue virus remains asymptomatic (90%). If they develop fever it could be one of the following.

  1. Undifferentiated febrile illness
  2. Dengue fever (DF)
  3. Dengue Haemorrhagic Fever (DHF)
  4. Unusual Dengue

What are the symptoms of dengue?

The common symptoms of dengue fever include high grade fever, severe headache, severe pain behind the eyes, joint pain, muscle pain, bone pain, nausea, vomiting, rash and sometimes mild bleeding,

What is dengue haemorrhagic fever?

DHF is the more severe form of dengue illness, characterized by fever that lasts from 2 to 7 days, in addition to the symptoms of simple dengue fever; which include persistent vomiting, severe abdominal pain, difficulty in breathing, dizziness, bleeding etc. There should be evidence of plasma leakage to detect the presence of DHF. Its clinical course changes as the disease progresses and consists of three stereotypic phases: Febrile phase, Critical phase and Convalescent Phase.

It is difficult to differentiate DF from DHF during the febrile phase of the illness. A patient with DHF may enter into the critical phase of the illness where the small blood vessels become leaky allowing the fluid component of the blood to leak into chest and abdominal cavities. This can lead to a reduction in the volume of blood and therefore poor blood supply to vital organs, such as the brain, kidneys & the liver. This may lead to failure of the circulatory system and shock, followed by death if circulatory failure is not corrected.

How does Dengue Fever and Dengue Haemorrhagic Fever spread?

Dengue is transmitted to humans by the bite of an infected female Aedes mosquito. The mosquito becomes infected when it bites a person who has the dengue virus in their blood. After about a week, the mosquito can transmit the virus while biting a healthy person. Person to person transmission of DF and DHF does not occur.

How can we manage a dengue patient who does not require admission to a hospital?

  1. Ensure adequate oral fluid intake. Approximate guide for fluid intake during this stage is age appropriate maintenance fluid requirement. This should consist of Oral Rehydration Solutions (ORS), king coconut water, fruit juices, kanji or soup. Exclude red and brown drinks.
  2. Adequate physical rest
  3. Adequate dose of paracetamol
  4. Tepid sponging for fever
  5. Avoid Non- Steroidal Anti-Inflammatory drugs (NSAIDS)
  6. Anti-emetics if necessary
  7. Review with full blood counts.
  8. Advice patients to return immediately for review if any warning signs develop (clinically not well with settling of fever, inability to tolerate oral fluids, refusal to eat and drink, feeling extremely thirsty, severe abdominal pain/vomiting, cold and clammy extremities. Not passing urine for more than 6 hours etc.)

How can we prevent dengue infection?

DF is transmitted through a mosquito. Therefore, the best way to avoid dengue infection is to prevent mosquito bites. Still there is no vaccine or preventive drug available for dengue infection. Hence, following tips are useful:

  • Avoid mosquito bites during the day time by wearing protective clothing and by using mosquito repellents. 
  • Use mosquito nets when sleeping (both day and night)
  • Get rid of mosquito breeding sites regularly in and around your household. These usually include discarded tyres, plastic containers, coconut shells, leaf axils, blocked roof gutters, bird baths, flower vases and other places that allows for collection of rain water.

What are the registered mosquito repellents that are available?

Given below is a list of chemicals that are registered under the Registrar of Pesticides that can be used as effective mosquito repellents.


Trade Name Active Ingredient and Strength Imported Company Registration Status

Category (RES/GEN/DOME)

 Mino 8  Ethylbutyl acetylaminopropionate 80g/L  George Steuart Health (Pvt) Ltd. Repellent  Domestic
 Soffell  N, N-diethyl-m-toluamide 13%  Rattan Merchant Repellent Domestic
 Soffell Spray  N,N-diethyl-m-toluamide 13%  Rattan Merchant Repellent Domestic
 Moso  Icaridin 20% (w/w)  EB Creasy Co. & Plc. Repellent Domestic


Where to complain?

If a person needs to complain regarding a possible dengue mosquito breeding place, it is always encouraged to have a discussion with the owner or the person responsible for the location where the breeding place is at regarding the problem. If it is not satisfactory, inform the relevant Public Health Inspector (PHI) and Medical Officer of Health (MOH) of the particular area. If it is a problem regarding disposal of solid waste, inform the Local Government institutions (i.e Municipal council/Town council / Pradeshiya sabha ,etc).