Dengue Fever : Clinical Presentation, Pathogenesis, Diagnostic Methods, Treatment & Management

Summary

Dengue fever, caused by the dengue virus transmitted through mosquitoes, is a serious disease that affects over 120 countries. Symptoms range from mild flu-like signs to severe forms, including dengue hemorrhagic fever and dengue shock syndrome. The virus has four serotypes, and secondary infections with a different serotype can lead to more severe complications. The disease progresses through three phases: febrile, critical, and convalescent. There is no specific antiviral treatment; supportive care, hydration, and close monitoring are crucial, especially for severe cases. Early detection and prevention are key to reducing the risks of severe complications.

Takeaways

• 😀 Dengue fever is a common arthropod-borne viral disease transmitted by Aedes mosquitoes, specifically Aedes aegypti and Aedes albopictus.
• 😀 Dengue affects over 120 countries worldwide, with symptoms ranging from mild flu-like illness to severe, life-threatening conditions like severe dengue (dengue hemorrhagic fever) and dengue shock syndrome.
• 😀 The dengue virus has four serotypes, and infection with one serotype gives lifelong immunity, but secondary infection with a different serotype can lead to severe dengue.
• 😀 The incubation period of dengue is 4 to 10 days, with symptoms lasting 2 to 7 days. About 1 in 4 infected individuals show symptoms.
• 😀 The clinical course of dengue infection has three phases: febrile phase, critical phase, and convalescent (recovery) phase.
• 😀 During the febrile phase, symptoms include high fever, headaches, muscle and joint pain, rash, nausea, and mild bleeding manifestations such as petechiae.
• 😀 A positive tourniquet test, which detects petechiae after a blood pressure cuff is applied, can be used to diagnose dengue during the febrile phase.
• 😀 The critical phase, which begins after fever subsides, lasts 24 to 48 hours and is marked by potential severe complications like plasma leakage, shock, and severe hemorrhage.
• 😀 In severe dengue, plasma leakage can lead to hypovolemic shock, which presents with hypotension, tachycardia, and altered consciousness.
• 😀 There is no specific antiviral treatment for dengue. Supportive care is crucial, including hydration and avoiding NSAIDs due to their anticoagulant properties. Close monitoring is essential for severe cases to prevent shock and organ damage.

Q & A

What is the primary mode of transmission of dengue virus?

Dengue virus is primarily transmitted by mosquitoes of the Aedes genus, specifically Aedes aegypti and Aedes albopictus. These mosquitoes spread the virus when they bite humans for a blood meal.

What are the four serotypes of the dengue virus, and how do they affect immunity?

There are four serotypes of the dengue virus. Infection with one serotype provides lifelong immunity against that specific serotype. However, a secondary infection with a different serotype can lead to severe dengue and dengue shock syndrome.

What are the key signs and symptoms during the febrile phase of dengue infection?

During the febrile phase, patients typically experience high-grade fever, severe headache (often with retro-orbital pain), joint pain, muscle pain, bone pain (called 'breakbone pain'), a rash, nausea, vomiting, and mild hemorrhagic manifestations like petechiae, purpura, and bleeding gums.

What is the tourniquet test, and how is it used in diagnosing dengue?

The tourniquet test involves inflating a blood pressure cuff to a level between systolic and diastolic blood pressure for 5 minutes. After removing the cuff, if there are more than 20 petechiae per square inch, the test is considered positive, indicating a potential dengue infection.

What warning signs should clinicians monitor for during the defervescence phase of dengue?

Warning signs during the defervescence phase include persistent vomiting, severe abdominal pain, fluid accumulation in pleural and peritoneal spaces, mucosal bleeding, difficulty breathing, restlessness, postural hypotension, hepatomegaly, and an increasing hematocrit.

What is the critical phase of dengue infection, and what complications can arise?

The critical phase begins after defervescence and typically lasts 24 to 48 hours. During this phase, some patients may experience reappearing fever, plasma leakage, hypotension, tachycardia, tachypnea, and reduced consciousness, leading to hypovolemic shock, bleeding, and organ complications.

What is the role of antibody-dependent enhancement (ADE) in severe dengue infections?

Antibody-dependent enhancement occurs during a secondary dengue infection when non-neutralizing antibodies bind to the virus. This interaction leads to the infection of more immune cells, increased viral replication, and severe vascular effects, which contribute to the severity of the disease.

What diagnostic tests are used for detecting dengue infection?

Diagnostic tests for dengue include nucleic acid amplification tests (like PCR), which detect viral genomic material in the first week of illness, and immunoassays that detect viral NS1 antigen. Serologic tests for detecting IgM antibodies are also used, especially if the patient presents after the first week.

What are the laboratory findings associated with dengue infection?

Common laboratory findings in dengue include thrombocytopenia (low platelet count), leukopenia (low white blood cell count), and mild to moderate increases in serum transaminases. Severe cases may also show increased hematocrit, hypoproteinemia, prolonged PT and APTT, and decreased fibrinogen levels.

How is dengue fever treated, and what is the role of supportive care?

There is no specific antiviral treatment for dengue. Supportive care is essential, including maintaining hydration to prevent dehydration, controlling fever with acetaminophen (and avoiding NSAIDs), and closely monitoring patients for complications like hypovolemic shock. For severe dengue, IV fluid administration and blood products like fresh frozen plasma may be needed.