Dengue: Causes, Symptoms, Diagnosis, Treatment and Prevention

It is the second most crucial mosquito-borne infection in morbidity, mortality, and economic costs.

Dengue is an infection by a common arbovirus that infects man. Four dengue viruses can transmit the disease.

Most dengue cases are found in tropical areas or countries around the world. A mosquito that has been infected with a dengue virus can transmit it even more.

The mosquito becomes infected after biting another person infected with the dengue virus.

Direct transmission from one person to another does not take place.

Dengue causes

Dengue fever is caused by one of four different but closely related viruses transmitted by one type of infected mosquito, frequently found in tropical and subtropical regions of the world.

Dengue fever is a mosquito-borne infection that requires a specific variety of mosquitoes: the Aedes mosquito to transmit it from person to person.


Dengue is caused by four dengue virus serotypes, namely DEN-1, DEN-2, DEN-3, and DEN-4, belonging to the genus Flavivirus and the family Flaviviridae.

Humans are the primary amplifying host for the virus. It is transmitted through the bite of infected female Aedes aegypti and Aedes albopictus mosquitoes.

The incubation period or the time between infection with the virus and the appearance of signs and symptoms is, on average, five to eight days.

Once you are infected with one of the strains, you must develop lifelong immunity against that strain. However, it is possible that the person could be re-infected with a different strain.

If the patient is re-infected with a different strain, they have a slightly higher chance of developing more severe complications.

The dengue virus transmission cycle occurs as follows: An infected person is bitten by a female mosquito that ingests the virus’s blood; it enters the cell through endocytosis and replicates in the epithelium of the intestines, the nerve ganglia: the fat body, and the salivary glands of the mosquito.

RNA serves as a messenger, and individual viral proteins are generated. Once the vision is fully formed, it is released via lysis of the cell.

This cycle lasts from eight to twelve days in the mosquito and will depend on the environmental conditions; once the mosquito has been infected, it remains infected throughout its life.

When the infected mosquito bites another human, the virus remains in the bloodstream, replicating, in target organs, such as the liver and local lymph nodes.

It then spreads through the blood and infects leukocytes and other lymphatic tissues, producing the various clinical pictures that characterize dengue, and thus the cycle continues.

Population growth and increased travel to infected areas have caused the virus to spread among different groups.

The Aedes mosquito prefers to live near water and is often found in standing water in containers around construction sites.

Dengue rates are often high in major cities in the developing world that have poor levels of sanitation.

The risk of contracting dengue increases when you spend much time living or working in developing towns and cities.

Dengue symptoms

Usually, people infected with the dengue virus do not experience any symptoms at all. Only 20% of all dengue cases have symptoms, and of these, only 5% have severe symptoms.

Dengue symptoms and signs depend mainly on the strain of the virus that caused the infection.

Type 1 and Type 3 are comparatively mild strains, while Type 4 is more robust and causes fever and decreased platelets.

Type 2 is the most dangerous strain of dengue that can cause hemorrhagic fever, organ failure, and dengue shock syndrome.

Dengue platelet counts can drop below 20,000, associated with spontaneous bleeding.

Dengue symptoms and signs appear after the incubation period, varying from 3 to 14 days.

After infection with the dengue virus, the disease is usually asymptomatic or undifferentiated.

The clinical characteristics of dengue can be divided into four types:

Undifferentiated fever

Undifferentiated fever is characterized by fever, malaise, pharyngeal infection, upper respiratory tract symptoms, and skin rash.

Dengue fever

The disease manifests as a sudden onset of a severe headache (mainly in the forehead), chills, pain behind the eyes that worsens with eye movement (retro-orbital pain), body aches, joint pain, and pain in the lower back, severe pain in the legs and joints (myalgias and arthralgias).

Body temperature rises rapidly to 40 ° C, with relatively low heart rate (bradycardia) and low blood pressure ( hypotension ).

Dengue rash is a bright red spot (petechiae) and usually appears first on the lower extremities and chest.

In some patients, it spreads to cover most of the body.

The glands (lymph nodes) in the neck and groin are often swollen. There may also be gastritis associated with abdominal pain, nausea, vomiting, or diarrhea.

Some cases develop much milder symptoms that can be misdiagnosed as influenza, chikungunya, or another viral infection when there is no rash.

Classic dengue fever lasts for about 6 to 7 days, with a smaller fever peak at the end of the illness (the so-called biphasic pattern).

Clinically, the platelet count will decrease until the patient’s temperature is average.

Hepatitis is seen in some cases of dengue fever, with elevated liver enzymes.

Central nerve symptoms with cerebral hemorrhage, edema, and rarely primary dengue encephalitis have been reported occasionally.

Dengue hemorrhagic fever

Dengue hemorrhagic fever is caused by heterologous serotypes and is characterized by increased vascular permeability, hypovolemic, and abnormal blood clotting mechanisms. The patient tends to become sweaty, irritable, and restless.

Symptoms often begin with a sudden rise in temperature and the appearance of facial flushing and other flu-like symptoms.

The fever generally lasts 2 to 7 days and can reach 41 ° C, possibly with the presence of seizures and new complications.

In recognition of dengue hemorrhagic fever, the symptoms are as follows:

  • Severe and continuous pain in the abdomen.
  • Nose, mouth, and gum bleeding or skin bruising.
  • Frequent vomiting with or without blood.
  • Black stools like coal tar.
  • Excessive thirst (dry mouth).
  • Pale and cold skin
  • Restlessness.
  • Drowsiness.

Dengue shock syndrome

The symptoms of dengue shock syndrome are characterized by hemorrhages that can be observed appearing in spots on the skin, such as petechiae and ecchymosis.

Any minor injury can cause heavy bleeding.

The patient may suffer a sudden deterioration in their condition, and the patient may go into a state of shock, which can cause death within 24 hours. However, the patient can recover with proper medical treatment.

Progression to dengue hemorrhagic fever or dengue shock syndrome occurs after 3 to 5 days of fever. By this time, the fever has often subsided.

This can be misleading to believe that the patient is headed for recovery.

This is the most challenging period and one that requires excellent medical vigilance.

Dengue shock syndrome is defined as a dengue hemorrhagic fever, but more severe:

  • Weak rapid pulse.
  • Narrow pulse pressure (less than 20mm Hg).
  • Cold, shaggy skin and restlessness.

In rare cases, it can present atypically with unusual symptoms such as:

  • Encephalopathy: can occur due to hyponatremia, cerebral edema, and microvascular.
  • Free bleeding.
  • Cardiomyopathy or myocarditis.
  • Mononeuropathy, polyneuropathy, Reye’s syndrome, Guillain-Barre’s syndrome.
  • Myelitis transversa.
  • Rhabdomyolysis.
  • Epidemic myalgia cruris: is a rare manifestation and hemorrhagic shock is its rare complication.
  • Acute liver failure.
  • Acute kidney failure.

The virus is found mainly in hepatocytes, Kuffer cells, and the endothelium, along with the formation of immune complexes.

Dengue diagnosis

The doctor will take a complete history of your symptoms (including their severity and duration) and perform a physical exam.

He will also look for the characteristic combination of fever, petechiae, and headache with dengue fever.

This combination of symptoms is known as the “dengue triad.”

In endemic areas where dengue is expected, a physical examination alone is sufficient for a diagnosis.

However, in cases where dengue symptoms are not definitive, dengue fever can be confused with other illnesses such as influenza, measles, malaria, or typhoid fever.

Your doctor may recommend dengue blood tests and tests to make a definitive diagnosis, as some of the symptoms of dengue are similar to chikungunya. This similar infection often occurs in the same areas as dengue.

Your doctor may perform the following tests to diagnose this condition:

  • Antibody titer for dengue virus types.
  • Complete blood count.
  • Polymerase chain reaction test for dengue virus types.
  • Liver function tests.

There are two main types of dengue tests:

Molecular tests

Molecular tests detect the genetic material of the dengue virus in the blood.

The onset of fever takes about one week for the test results to be accurate.

However, this test can determine the type of serotype causing the infection, so dengue fever treatment can be modified accordingly.

Some of these tests can also distinguish between dengue, Zika, and chikungunya, as these three mosquito-borne diseases often have similar symptoms.

Antibody tests

Antibody tests are used to detect the body’s antibodies in response to the dengue virus.

These dengue tests are often used to confirm a diagnosis in the later stages of infection.

These antibodies are often produced after 5 to 7 days from infection.


Group A

Patients can be treated at home.

  • Encourage oral intake of oral rehydration solution, fruit juice, and other fluids. Adequate oral fluid intake can reduce the number of hospitalizations.
  • Administer paracetamol for high fever if the patient feels uncomfortable. The dosage interval for paracetamol should not be less than six hours. Place warm sponges if the patient still has a high fever.

The patient should be taken to the hospital immediately if any of the following situations arise:

There is no clinical improvement, deterioration at the time of defervescence, severe abdominal pain, persistent vomiting, cold and clammy extremities, lethargy, irritability or restlessness, bleeding with black stools or vomiting coffee, no urination for more than 4 to 6 hours.

B Group

Patients require hospital administration for close observation, especially as they approach the critical phase.

If the patient has dengue with warning signs, the action plan should be as follows:

Perform a hematocrit test before starting fluid therapy.

Administer only isotonic solutions, such as 0.9% saline, Ringer’s lactate, or Hartmann’s solution.

Starting with 5 to 7 ml per kg per hour for 1 to 2 hours, then reduce to 3 to 5 ml per kg per hour for 2 to 4 hours, and then reduce 2 to 3 ml per kg per hour or less according to with the clinical response of the patient.

Reassess clinical status and repeat hematocrit.

If the hematocrit remains the same or only increases minimally, continue at the same rate of 2 to 3 ml per kg for another 2 to 4 hours.

If vital signs are worsening and hematocrit increases rapidly, the rate should be increased to 5-10 ml per kg per hour for 1 to 2 hours.

Again the clinical status of the patient is evaluated, the hematocrit is repeated, and the urine output of approximately 0.5 ml per kg per hour is monitored.

Intravenous fluids are usually needed for only 24 to 48 hours.

This is indicated by adequate urine output and oral fluid intake or when a stable patient’s hematocrit falls below baseline.

If the patient has dengue without warning signs, the action plan should be as follows:

  • Stimulate Oral Fluids: If not tolerated, begin intravenous fluid therapy of 0.9% saline or Ringer’s lactate with or without dextrose at the maintenance rate. Patients can drink oral fluids after a few hours of intravenous fluid therapy. Therefore, it is necessary to check the infusion of fluids frequently.
  • Patients should be monitored for temperature pattern, the volume of fluid intake and loss, urinary output (volume and frequency), warning signs, hematocrit, and white blood cell and platelet counts.

Group C

Patients requiring emergency treatment.

In this group are patients who require emergency treatment and urgent referral when they are in the critical phase of the disease.

Patients must be admitted to intensive care. Intravenous fluid resuscitation is the essential and generally the only intervention.

The crystalloid solution must be isotonic and of sufficient volume to maintain adequate circulation during the plasma filtration period.

If possible, obtain hematocrit levels before and after fluid resuscitation.

There should be continuous replacement of more plasma losses to maintain adequate circulation for 24 to 48 hours.

Blood transfusion should be given only in cases of suspicious or severe bleeding.

Group D

Shock treatment is the action plan to treat patients with compensated shock and is as follows:

  • Initiate intravenous fluid resuscitation with isotonic crystalloid solutions at 5 to 10 ml per kg for one hour. Then the patient’s condition is reassessed: vital signs, capillary filling time, hematocrits, and urine output.
  • If the patient’s condition improves, intravenous fluids should be gradually reduced to 5 to 7 ml per kg per hour for 1 to 2 hours, then 3 to 5 ml per kg per hour for 2 to 4 hours, then 2 to 3 ml per kg per hour, and then depending on the hemodynamic state, which can be maintained for up to 24 to 48 hours.


There is no vaccine for dengue fever.

Prevention involves avoiding being bitten by mosquitoes in regions where dengue fever is prevalent.

The following measures are recommended for protection against dengue infection:

  • Wear clothing and hats that cover the arms, legs, and head.
  • Wear shoes instead of sandals.
  • Apply the insect repellent to the skin. The most effective repellants contain diethyltoluamide, at a concentration between 30% and 50%.
  • Apply permethrin insecticide to clothing.
  • Use nets impregnated with permethrin.
  • Use electrical insect repellants or mosquito repellants in the areas of the home or workplace.
  • When possible, stay in an accommodation with screens on doors and windows or air-conditioned.