Dengue Fever

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Dengue Fever

What is Dengue fever (DF) or Break-bone fever?

Dengue fever is an acute viral infection caused by at least four different strains of Dengue virus. Classic dengue begins suddenly with an influenza-like syndrome consisting of fever, malaise, cough and headache. Severe pains in muscles and joints (breakbone) occur. Enlarged lymph glands, rash and low WBC counts are common. After a week or so, the symptoms regress but weakness may persist.

What are Dengue haemorrhagic fever (DHF) & Dengue shock syndrome (DSS)?

Dengue haemorrhagic fever (DHF) is a severe form of Dengue fever caused by infection with more than one Dengue virus. The patient suffering from Dengue haemorrhagic fever develops bleeding from nose, gums or skin. Sometimes, thepatient may have coffee colored vomiting or black stools. This indicates bleeding in gastro intestinal tracts which is serious. Rarely, the patient suffering from dengue may manifest rapid & weak pulse, low blood pressure, cold clammy skin and restlessness (manifestations of shock), then it is called Dengue shock syndrome (DSS).

When should Dengue be suspected?

Dengue should be suspected when there sudden onset of high grade fever (103-105 degrees F or 39-40 degrees C). The fever is accompanied with severe headache (mostly in the forehead), typically pain behind the eyes, body aches and joint pains, rash on the skin and nausea or vomiting. The fever usually lasts for 5-7 days. All the above symptoms and signs may not be present in the patient.

When does a suspected case become a probable case of Dengue?

If a patient suspected to be having dengue has reduced platelet* count (less than one lac/cubic mm) or an increase in blood hematocrit* (20% or more, than base line value), then the patient is considered to be a probable case of Dengue. Patients with dengue may not have a high hematocrit, if the person was anemic (low hemoglobin) to start with.

*Platelets help to stop bleeding and Haematocrit indicates hemoconcentration (i.e. thickness of blood).

How is a probable case of Dengue confirmed?

The diagnosis can be confirmed by isolation of virus in cell culture (direct evidence) or by serological test that demonstrate the presence of IgM antibody or four fold rise in antibody titer during disease (indirect evidence). The tests for confirmation of Dengue should be done in reliable laboratories.

How does one get Dengue?

Dengue occurs following the bite of an infected mosquito known as Aedes aegypti. It breeds in clean, stagnant water and has a flight range of 100 – 200 metres. The mosquito gets the Dengue virus after biting a human being infected with Dengue virus.

What are the typical characteristics of Dengue mosquito (Aedes aegypti)?

Aedes aegypti is can be easily recognized by its peculiar white spotted body and legs. It is a domestic mosquito which 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 the homes, and other dwellings. These eggs will develop, become larvae, and further develop into adults in about 10 days. It is to be noted that the mosquito is day biter and the bite is likely to go unnoticed as it does not cause deep skin irritation/ eruption like other mosquito bites.

How can Dengue mosquitoes be controlled?

Dengue mosquitoes breed in stagnant, exposed water collections. To prevent the mosquitoes from breeding, drain out the water from air coolers (when not in use), tanks, barrels, drums, buckets etc. Destroy discarded containers in which water collects e.g. bottles, plastic bags, tins, used tyres etc.

In case it is not possible to drain out various water collections or to fully cover them, use Abate, an insecticide, 1 part per million to prevent larvae from developing into adults.

How can mosquito bites be prevented?

Dengue is caused due to bite of mosquito carrying the dengue virus during the day time throughout the day; highest biting intensity is about 2 hours after sunrise and before sunset.


Following measures can protect an individual from all mosquito bites:

  • Wear full sleeve clothes and long dresses to cover as much of body as possible


  • Use mosquito coils, electric vapour mats and ointments during the daytime, as well


  • Use mosquito nets to protect children, old people and others who may rest during the day. The effectiveness of these nets can be improved by treating them with permethrin (insecticide). This bed-net is called Insecticide Treated Nets


How does Dengue spread from one person to another?

Dengue can only spread through the bite of an infected mosquito.

After getting the infection, how much time does it take to develop Dengue?

The symptoms of Dengue develop generally after 4-6 days of infection, when the virus has multiplied in sufficient numbers in the lymph glands in the body.

Do all people suffering from Dengue appear ill?

Many people infected with the Dengue virus do not suffer from any signs or symptoms of the disease. There may be 4-5 persons with no symptoms (or with very mild symptoms), for every patient with signs and symptoms of Dengue.

Is it always necessary to get admitted to the hospital if one is suffering from Dengue?

No, many patients with Dengue can very well be treated at home. They should take enough rest, drink plenty of fluids (Oral Rehydration Salt/ORS commonly used in treating diarrhea, is preferable) and eat nutritious diet. Sufficient fluid intake is very important. However, it is important to look for danger signs and inform the doctor immediately.

What are the danger signs in Dengue for which one needs to consult a doctor immediately?

The signs and symptoms that are considered to be serious include severe pain in the abdomen, persistent vomiting, bleeding in the skin appearing as small red or purplish spots, bleed through nose, bleeding from gums, passage of black stools like coal tar.

As soon as severe pain in the abdomen and persistent vomiting are detected, it is better to bring the patient to the hospital.

What is the treatment for Dengue?

Like most viral diseases there is no specific treatment for Dengue. Paracetamol is the drug of choice to bring down fever and relieve joint pain. Other medicines such as Aspirin and Ibuprofen should be avoided because of increased risk of bleeding. Antibiotics are usually not required.

Can Dengue fever turn dangerous?

Most people who suffer from Dengue fever recover in 1-2 weeks time and usually there is no risk of death.  Sometimes, the infection can become dangerous since it may cause damage to the blood vessels causing leakage of blood fluid/plasma into various organs (condition known as Dengue Haemorrhagic Fever or Dengue Shock Syndrome). Good treatment provided in time can save most lives.

Is it possible to get dengue again after suffering from it once?

Dengue can occur because of 4 different but related strains of dengue virus. If a person has suffered from one virus, there can be a repeat occurrence of dengue if a different strain is involved subsequently. Being affected by one strain offers no protection against the others. Therefore, it is possible to get dengue more than once.

Are there any vaccines available to prevent Dengue?

Due to increased tendency of viruses to mutate into more serious forms, it is imperative to have Dengue vaccines at the earliest. As yet, there are no vaccines available in the market.

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