Dengue Fever (Break-bone fever)

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• The patient blood is needed.

Definition of Dengue Fever

1. The Dengue virus causes dengue fever. It is also called Break-Bone Fever.
2. It is an endemic tropical disease due to single-stranded RNA belonging to the Flavivirus genus.
3. It is transmitted by the Aedes aegypti mosquitoes.

Epidemiology of Dengue Fever

1. Dengue fever is the most common and most important arthropod-born viral (arbovirus) disease most common in tropical and subtropical people.
2. It is transmitted by mosquitos.
3. Its incidence recently increased to 40% to 50% of the world population is at risk.
4. People living or traveling to tropical countries are at risk
5. Four serotypes of the Dengue (DEN) virus (Flavivirus) cause dengue fever.
   1. DEN-1
   2. DEN-2
   3. DEN-3
   4. DEN-4
6. It may lead to:
   1. Dengue hemorrhagic fever.
   2. Dengue shock syndrome.

Dengue virus structure:

1. Dengue virus is a roughly spherical virus.
2. It is composed of a viral genome (RNA).
3. Surrounded by viral capsid.
4. Then is the viral envelope.
5. Outermost is the shell of protein.

Spread of dengue virus:

Dengue fever is transmitted by mosquitoes, and there are two types.

1. Aedes aegypti.
2. Aedes albopictus
3. The Serotypes of Dengue virus (DEN virus) distinguished by Complement fixation and neutralization test are:
   1. Dengue  Den-1
   2. Dengue Den-2
   3. Dengue Den-3
   4. Dengue Den-4
4. Immunity is specific to each serotype.
5. Dengue virus is transmitted by female mosquitoes, mainly of the species Aedes aegypti and, to a lesser extent, Aedes albopictus.
   1. These types of mosquitoes are present throughout the world. These Insects that transmit disease are called vectors.
   2. The disease is widespread throughout the tropics and is influenced by rainfall, temperature, and unplanned urbanization.
   3. This will spread to susceptible populations, usually by the viremic travelers; in that case, epidemic spread ranges from 50% to 70%.
6. WHO estimates that about 40% of the world population is at risk. There is no discrimination of the age group because all age groups are at risk.
7. The epidemic of dengue hemorrhagic fever occurred in the last 20 years in East Africa, Sri Lanka, and Latin America.
8. Dengue is the second febrile disease after malaria in travelers coming from developing countries.

Dengue fever spread

 Immunity to Dengue Fever:

1. Recovery from infection by one serotype provides lifelong immunity against that serotype.
2. But still, you are at risk of the other three sub-serotypes.
   1. There is no direct spread from the patient. So no worry about handling the patient.
3. Cross-reactive immunity is partial and temporary.

Dengue fever spread

Signs and Symptoms of Dengue Fever:

1. The incubation period is usually 4  to  7 days after the mosquito bite.
   1. History of travel from the dengue-endemic area.
2. Dengue infection may range from:
   1. Asymptomatic patients.
   2. Severe hemorrhagic fever.
   3. Dengue shock syndrome (Fatal shock).
   4. Dengue hemorrhagic fever is seen more commonly in children than adults.
3. Dengue fever is a self-limited biphasic fever disease.
4. 50% of the children are asymptomatic.
   1. This disease is more severe in adults.
5. After the incubation period:
   1. The patient has flu-like signs and symptoms.
6. These signs and symptoms last for  3  to 10 days.
7. In some cases, it becomes lethal and is called severe Dengue fever.
   1. There are sudden:
      1. Fever, mostly high-grade fever.
      2. The patient may have chills.
      3. The fever is biphasic, initially 3 to 7 days, and then remission a few hours to 2 days.
      4. There is a sore throat.
      5. There is a headache.
      6. Muscle pain leads to severe myalgias.
      7. Joint pain (arthralgias). This is more common in serotype 2.
8. There is a characteristic skin rash like measles. These rashes may be in the maculopapular, morbilliform, or petechial form.
9. 25% of the cases may show heart involvement.
10. 5% may show fulminant hepatitis.
11. The patient may go into depression.
12. When the disease is severe and may lead to bleeding, it is called  Dengue hemorrhagic fever due to low platelet count.
    1. High fever, hypotension, hemorrhage (GI bleeding), and shock are usually due to second or third-time infection.
13. Another complication is low blood pressure which leads to Dengue shock syndrome.
14. Some patients may show the following:
    1. Ecchymosis.
    2. Gastrointestinal bleeding.
    3. Epistaxis.
15. In the case of dengue hemorrhagic fever, may see:
    1. Restlessness.
    2. Epistaxis.
    3. Abdominal pain.
    4. The gastrointestinal area may show bleeding, tenderness, and ascites.

Prevention of Dengue Fever:

1. There is no commercially available Vaccine.
2. Try to stay away from the affected area.
3. Try to reduce or eradicate the mosquitoes in that area.
4. Try to avoid biting by this mosquito.
5. Do the proper disposal of waste and garbage.
6. Try to remove all possible places where the mosquito can survive.
7. Apply adequate insecticides to water storage containers every week.
8. Try to stop the entry of mosquitoes from the windows or doors.

Diagnosis of Dengue Fever:

1. This may be diagnosed with the signs and symptoms of fever, nausea, vomiting, rashes, and generalized pain.
2. Laboratory tests are:
   1. Low blood count (WBC are 2000 to 5000 /µL).
      1. WBC shows toxic granulations, and there are marked atypical lymphocytes.
   2. Low platelets count.
   3. Positive tourniquet test.
   4. Raised hematocrit due to hemoconcentration.
   5. ESR is usually normal if it is raised before considering another differential diagnosis.
3. Confirmatory tests are virus isolation. This can be done in cell culture.
   1. Virus isolation is possible in the acute phase of the disease. Virus culture is positive within the first 5 days of infection, where the sensitivity is <50%.
   2. Can take a culture from the liver autopsy tissue.
   3. The virus can be detected from CSF or serum by ELIZA.
   4. PCR -Nucleic acid detection by PCR can be done.
   5. Viral antigen (NS1) can be detected. This is positive in more than 90% of the primary infection in the febrile phase.
4. Serological tests detect dengue virus-specific antibodies.
   1. These antibodies are of:
      1.  IgM antibody. This can be detected by ELIZA within 5 days and persists for months.
         1. Diagnosis of the disease in the later stages of the infection.
      2. IgG antibody appears soon after IgM, and it persists for life; titer may be 1:1280
      3. Both IgG and IgM are produced after 5 to 7 days.
      4. IgM antibody indicates acute primary infection. This is undetectable after primary infection for up to 30 to 90 days.
         1. IgM may be produced in reinfection.
5. Liver function tests show raised transaminases (these may be 500 to 1000 U/L).

Complications of Dengue Fever:

1. There may be:
   1. Respiratory involvement like pneumonia.
   2. Hepatitis.
   3. Orchitis.
   4. Oophoritis.
   5. Retinal hemorrhage.
   6. Depression.
   7. Encephalitis.
   8. Bacterial superinfection may occur in older patients.
   9. Dengue hemorrhagic fever is characterized by a decreased platelet count.
   10. Dengue shock syndrome

Treatment of Dengue Fever:

1. For pain, give pain reliever drugs. Acetaminophen can be used. Avoid Aspirin and NSAIDs because they may cause bleeding.
2. In the case of hemorrhagic dengue or fever, the patient needs plenty of fluids.
3. There is no vaccine available.
4. WHO reported in late 2015 and early 2016 that the first Dengue vaccine “Dengvaxia (CYD-TDV), by the company Sanofi Pasteur, was registered for some countries. This can be used between the ages of 9 to 45 years for people living in endemic areas.

The outcome of the disease:

• There may be a 2.5% mortality due to dengue fever.

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