Causes

The virus of dengue fever belongs to the family flaviviridae. It is the RNA virus. Other member of the Flaviridae virus is the virus of yellow fever, virus of West Nile, virus of encephalitis of St. Louis, virus of Japanese encephalitis, virus of encephalitis of...

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Effects

The children who are below the age of 10 years get affected on the functioning of circulatory system during the dengue fever. The mortality rate lies in between the 6 to 30% and it is found that most of the death occurred in the patients of dengue...

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Treatment

It is found that at present there is no specific vaccine is found which can kill the virus of dengue fever not even a single anti virus tablets.
Dengue fever is treated by a medicine which is known as Paracetamol, an anti pyretics...

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Dengue Fever Testing

How is it used?

The testing of dengue fever is done to determine whether the recent potential exposure and symptoms of the person body has been infected by dengue or not. It is difficult to diagnose the infection without doing laboratory tests as the symptoms initially may resemble like diseases like malaria. There are 2 types of testing available:

  • Antibody tests— primarily these tests are used to help in diagnosing a recent or current infection. 2 different antibodies classes are detected by them that are produced by body in response to the infection of dengue fever, IgM and IgG. A combination of both these tests is required for diagnosis due to reason that the immune system of the body produces different antibodies levels during the time of illness. IgM antibodies are 1st produced and tests for it are most effective at the time when they are performed 7-10 days later the exposure. For some weeks, the blood levels rise and then decrease gradually. After some months, the IgM antibodies gets fall down below the detectable levels. They are produced slower than the rate of infection. The level rises typically with the acute infection, it stabilizes and then it persists long-term. All those who get exposed to it prior to current infection, maintains IgG antibodies level in the level that affects the diagnostic results’ interpretation.
  • Molecular testing (PCR, polymerase chain reaction)— this test detects dengue virus’s genetic material in blood till 5 days of the symptom onset.

When is it ordered?

Testing might be ordered at the time when people have symptoms and signs associated with dengue at tropical locations where it is present. Main symptoms and signs include:

  • Low count of white blood cells
  • Easy bruising
  • Nose and gum bleeds
  • Bone, muscle or joint pain
  • Pain behind eyes or severe headache
  • Sudden high fever (40°C or 104°F)

Usually testing is ordered within 1 to 2 weeks of the starting of the symptoms for detecting the infection. If the antibody testing is done, an additional sample of the blood is collected after 2 weeks of the symptoms in order to determine whether the level of antibody is rising.

What does the test result mean?

  • Antibody testing— the test may have negative or positive result or might be reported as the antibody titer having an interpretation of the type of antibody (IgM or IgG) present.

Positive IgG and IgM tests detected for the dengue antibodies in the blood means that the person has become infected within recent weeks with the dengue virus. If IgG comes positive but IgM is negative or low, then it is probably that the person has got an infection earlier in past. If the titer of dengue IgG antibody increases from 1:4 to 1:64 between the initial samples then it is likely to have recent infection.

Negative IgG and/or IgM antibodies means that the person tested is not having any infection and the symptoms are because of any other reason or the antibody level may be very low for measuring. The individual might still have dengue infection- it might be just that it is very soon after the virus exposure to give a detectable antibody level.

The table as follows summarizes the results seen with the antibody testing:

IgM Result

IgG Result

Possible Interpretation

Positive

Negative

Current infection

Positive

Positive

Current infection

Low or negative or not tested

Four-fold increase in samples taken 2-4 weeks apart

Recent infection

Low or negative

Positive

Past infection

Negative

Negative

Too soon after initial exposure for antibodies to develop or symptoms due to another cause 

 

  • Molecular testing— the most reliable of all diagnosis is the PCR test that is considered as it detects the virus presence in the body but it is not available widely. A positive PCR result is considered conclusive. A PCR test having negative result indicates no infection present or low level of virus to detect if the test gets performed after the period of 5-day window since the time when the virus being present in the blood sample is collected. If recent exposures are suspected, then repeating the tests may be warranted later.

Is there anything else I should know?

Physical symptoms such as aching joints or rash are not dependable means to diagnose dengue fever due to the reason that the symptoms are not much likely to reflect after the fever has passed initially.

The antibody test can come positive if the individual is infected with any other arbo-virus like West Nile virus. The health practitioner would consider the test results of a person along with recent travel history and medical history while diagnosing.

No test at laboratory can predict whether the infection would progress or not to more severe forms.