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What you wanted to know about Dengue fever

Posted Aug 11 2011 12:00am
What is Dengue fever (DF)? What are Dengue haemorrhagic fever and Dengue shock syndrome?

Dengue [pronounced Den' gee] infection is caused by a virus. There are 4 types of Dengue viruses,namely DENV 1, DENV 2, DENV 3, and DENV 4. It occurs commonly as dengue fever. Occasionally the patient suffering from dengue may develop bleeding. Common sites for bleeding are nose, gums or skin. Sometimes, the patient may have coffee ground vomiting or black stools. This indicates bleeding in gastro intestinal tracts and it is serious. The patient with dengue who has bleeding has dengue haemorrhagic fever (DHF ). Rarely the patient suffering from dengue may develop shock because of low blood pressure, then it is called dengue shock syndrome ( DSS). DHF and DSS are common in persons who had a previous infection with another type of Dengue virus.

How do one get infected with Dengue virus?

The Dengue viruses are transmitted to humans by the bite of an infected mosquito. The Aedes aegypti mosquito is the most important transmitter or vector of dengue viruses, although many of the recent outbreaks were transmitted by Aedes albopictus. It is estimated that there are over 100 million cases of dengue worldwide each year.


Aedes aegypti has a peculiar white spotted body and legs and is easy to recognize even by laymen. It breeds in clean water and has a flight range of only 100 – 200 metres.The mosquito gets the Dengue virus after biting a human being infected with dengue virus.

 When does dengue develop after getting the infection?


After the entry of the virus in the person, it multiplies in the lymph glands in the body. The symptoms develop when the virus has multiplied in sufficient numbers to cause the symptoms. This happens generally about 4-6 days ( average) after getting infected with the virus.

Can people suffer from dengue and not appear ill?

Yes. There are many people who are infected with the virus and do not suffer from any signs or symptoms of the disease. For every patient with symptoms and signs there may be 4-5 persons with no symptoms or with very mild symptoms.

When should I suspect Dengue?

Dengue should be suspected when you have sudden onset of fever WITHOUT cough,cold,pain on urination etc. The fever is high 103-105 degrees F or 39-40 degrees C. It is accompanied with severe headache (mostly in the forehead), pain behind the eyes, body aches and pains, rash on the skin and nausea or vomiting. The fever lasts for 5-7 days. In some patients, fever comes down on 3rd or 4th day but comes back. All the above symptoms and signs may not be present in the patient. The patient feels much discomfort after the illness.

How does Dengue fever differ from other type of fevers?

Fever is usually abrupt in onset and very high.There wont be any running nose,cough etc.Slowly rising fever peaking only in few days time is unlikely to be Dengue fever.The characteristics of dengue that make it different from other causes of fever are the pain behind the eyes, severe pains in the muscles, severe bone and joint pains, and skin rashes. These features make the diagnosis of suspected Dengue likely. Even though there is joint pains there wont be any joint swellings as in Chikungunya fever.The severe bone pains caused by DF is the reason why DF is also called break-bone fever.

Generally, younger children and those with their first dengue infection have a milder illness than older children and adults.


Dengue hemorrhagic fever is characterized by a fever that lasts from 2 to 7 days, with general signs and symptoms consistent with dengue fever. When the fever declines, symptoms including persistent vomiting, severe abdominal pain, and difficulty breathing, may develop. This marks the beginning of a 24- to 48-hour period when the smallest blood vessels (capillaries) become excessively permeable (“leaky”), allowing the fluid component to escape from the blood vessels into the peritoneum (causing ascites) and pleural cavity (leading to pleural effusions). This may lead to failure of the circulatory system and shock [lack of blood supply/oxygen to tissues], followed by death, if circulatory failure is not corrected. In addition, the patient with DHF has a low platelet count and hemorrhagic manifestations, tendency to bruise easily or other types of skin hemorrhages, bleeding nose or gums, and possibly internal bleeding.

How is the diagnosis of dengue is confirmed?

There are laboratory tests that provide direct or indirect evidence for dengue fever. These tests provide evidence for the occurrence of dengue infection. There are some additional tests that can help to identify the type of dengue infection. The tests for confirmation of Dengue should be done in reliable laboratories.

The method used for diagnosis varies depending on its availability,cost, speed of obtaining the result and reliability. It also very much depend on when during the course of the disease blood sample is taken.

Can dengue fever be treated at home?



Most patients with dengue fever can be treated at home. They should take rest, drink plenty of fluids that are available at home and eat nutritious diet. Whenever available, Oral Rehydration Salt/ORS (commonly used in treating diarrhoea) is preferable. Sufficient fluid intake is very important and becomes more important in case DF progresses into DHF or DSS where loss of body fluid / blood is the most salient feature.It is important to look for danger signs and contact the doctor as soon as any one or more of these are found.


What is the treatment?


Like most viral diseases dengue fever can subside on its own.Paracetamol is the main stay to reduce fever.Pain killers/anti inflammatory agents like Aspirin/Brufen should be avoided  since they can increase the risk of bleeding.. Antibiotics do not help. Doctors should be very careful when prescribing medicines. Any medicines that decrease platelets should be avoided.

 Symptomatic management is the main stay of treatment.

When should a patient suffering from Dengue go to the hospital or consult a doctor?


Generally the progress towards dengue haemorrhagic fever or dengue shock syndrome occur after 3-5 days of fever. At this time, fever has often come down. This may mislead many of us to believe that the patient is heading towards recovery. In fact, this is the most dangerous period that requires high vigilance from care-givers. The signs and symptoms that should be looked for are severe pain in the abdomen, persistent vomiting, bleeding from any site like, bleeding in the skin appearing as small red or purplish spots, nose bleed, bleeding from gums, passage of black stools like coal tar. Bring the patient to the hospital whenever the first two signs, namely, severe pain in the abdomen and persistent vomiting are detected. Usually it is too late if we wait until bleeding has occurred.

The most dangerous type of dengue is the dengue shock syndrome. It is recognized by signs like excessive thirst, pale and cold skin (due to very low blood pressure), restlessness and a feeling of weakness.

Can dengue fever become dangerous?


The infection can become dangerous since it may cause damage to the blood vessels. The damage may range from increased permeability of the blood vessels, causing leakage of blood fluid/plasma into various organs to completely broken blood vessels that causes bleeding.The symptoms and signs of dengue haemorrhagic fever and dengue shock syndrome are related to damage to the blood vessels and derangement in functioning in components of blood that help it to clot. Mortality in DSS is around 1-5%.
What should the doctors treating dengue do ?

Patients suspected to be suffering from dengue haemorrhagic fever or dengue shock syndrome should be admitted to a hospital without delay.

The progress of these patients should be monitored regularly at 1-2 hours interval.

Platelet counts and haematocrits should be monitored repeatedly to review the progress of patients.


If the haematocrit levels fall dangerously then a blood transfusion should be considered. A fall of more than 20 % as compared to previous levels may be an indication for transfusion.


If the haematocrit values rise the patient should be given fluids intravenously and the fluids carefully monitored to ensure that the patient does not get excess fluids. A rise of Hematocrit more than 20 % as compared to previous levels may be an indication for IV fluids. The doctor should decide based on best judgement of patient's condition.


What should the doctors treating dengue avoid?


Do not prescribe aspirin and brufen or any other medicine that reduces the platelets or increases the tendency to bleed.

Avoid giving too much IV fluids unless the patient is bleeding or the haematocrit level is rising progressively.
Avoid rushing into giving blood transfusion unless the haematocrit is falling dangerously.
Do not give platelet transfusion unless the platelet count is very low or unless there is bleeding.


Can you get dengue again after suffering from it once?


It is possible to get dengue more than 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. 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. There is good evidence that sequential infection increases the risk of developing DHF because this partial immunity produces severe immune reaction in the body.


What is the Global incidence of dengue?


The incidence of dengue has grown dramatically around the world in recent decades. It is a disease of the tropical and sub-tropical regions Some 2.5 billion people – two fifths of the world's population – are now at risk from dengue. WHO currently estimates there may be 50 million dengue infections worldwide every year.The disease is now endemic in more than 100 countries Before 1970 only nine countries had experienced DHF epidemics, a number that had increased more than four-fold by 1995.
 Where does the mosquito that spreads dengue live?

What is the incidence and mortality of DHF?
An estimated 500 000 people with DHF require hospitalization each year, a very large proportion of whom are children and young adult. About 2.5% of those affected die.

Why there is an increasing incidence of severe Dengue infection World-wide?
Rapid and disorganised Urbanisation,poor solid waste management and lack of running water, leading to  storage of water in households etc are some of the factors that is causing an enormous increase in Dengue infections.


The highly domestic mosquito Aedes aegypti 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.


How can the multiplication of mosquitoes be reduced?

Dengue mosquitoes breed in stored, exposed water collections. Favoured places for breeding are barrels, drums, jars, pots, buckets, flower vases, plant saucers, tanks, discarded bottles, tins, tyres, water coolers etc.

To prevent the mosquitoes from multiplying, drain out the water from desert coolers/window air coolers (when not in use), tanks, barrels, drums, buckets etc. Remove all objects containing water (e.g. plant saucers etc.) from the house. Collect and 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 TEMEPHOS, an insecticide, ( brand name Abate) 1 part per million according to the local guidelines to prevent larvae from developing into adults.


How can I prevent mosquito bites to prevent dengue?

There is no way to tell if a mosquito is carrying the dengue virus. Therefore, people must protect themselves from all mosquito bites.

Dengue mosquitoes bite during the day time throughout the day. Highest biting intensity is about 2 hours after sunrise and before sunset.
Wear full sleeves clothes and long dresses to cover as much of your body as possible.

Use repellents- be careful in using them in young children and old people. Use mosquito coils and electric vapour mats during the daytime also to prevent dengue.

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 (pyrethroid insecticide). This bed-net is called Insecticide Treated Nets and are widely used in the prevention of malaria.


Is there any advice for the patient with dengue fever to prevent the spread of the disease to others?

The spread of dengue from a patient to others is possible. The patient should be protected from contact with the mosquito. This can be achieved by ensuring that the patient sleeps under a bed-net. Effective mosquito repellents are used where the patient is being provided care. This will prevent the mosquito from biting the patient and from getting infected and spreading it to others.



I am sure there will be many more questions about Dengue fever. Feel free to ask them in the comments column of this post.I will try my best to answer.


This post is dedicated to all those who tragically succumbed to Dengue infection and their families, especially to this young woman.  blogger .

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