Dengue Fever Overview

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Questions and Answers

What is indicated by a positive tourniquet test?

Lack of hemorrhagic manifestations

High platelet count

Presence of thrombocytopenia (correct)

Normal blood clotting

How can specificity be increased in the diagnosis of thrombocytopenia?

By using a cutoff of ≥20 petechiae per square inch (correct)

By decreasing the number of required petechiae

By examining the patient's travel history

By using a cutoff of ≥10 petechiae per 2.5 cm²

During which phase of dengue might a temperature drop indicate that the patient is in a critical phase?

Convalescent phase

Initial fever phase

Defervescence phase (correct)

Acute infection phase

What is the most important question to initially ask a patient to assess for dengue risk?

Where do you live? Signup and view all the answers

Which of the following is a hemorrhagic manifestation associated with dengue?

Gingival bleeding Signup and view all the answers

Which of the following is true regarding the relationship between shock and the tourniquet test?

The tourniquet test is less likely to be positive in shock. Signup and view all the answers

What is the causative agent of dengue fever?

Dengue virus from the Flaviviridae family Signup and view all the answers

How long can a mosquito transmit the dengue virus after becoming infected?

For the rest of its life Signup and view all the answers

What is the typical incubation period for dengue after a mosquito bite?

4-7 days Signup and view all the answers

Dengue fever has how many identified serotypes?

Four Signup and view all the answers

Which statement about the dengue virus serotypes is true?

Each serotype provides short-term cross immunity. Signup and view all the answers

In which season do dengue cases typically peak in the Philippines?

Rainy season Signup and view all the answers

What mechanism does the mosquito use to prevent blood from clotting while feeding?

Anticoagulants in its saliva Signup and view all the answers

What is the estimated number of dengue cases globally as of March 2024?

200 million Signup and view all the answers

What is the role of genetic variation within dengue virus serotypes?

Some variants may be more virulent. Signup and view all the answers

What does the presence of more than 10 petechiae typically indicate?

The patient may be prone to bleeding. Signup and view all the answers

What is a sign of severe dengue related to plasma leakage?

High hematocrit levels. Signup and view all the answers

What can result from a cytokine storm in severe dengue?

Increased plasma leakage. Signup and view all the answers

What is a potential neurological symptom of severe dengue?

Lethargy or coma. Signup and view all the answers

What does the IgM antibody indicate in primary dengue infection?

It is the first antibody to appear after infection. Signup and view all the answers

What describes the immunity conferred by primary dengue infection?

Lifelong immunity to the specific serotype. Signup and view all the answers

What is a symptom indicative of severe gastrointestinal involvement in dengue?

Persistent vomiting. Signup and view all the answers

What does the term 'hemorrhagic syndrome' refer to in severe dengue?

Increased bleeding potential. Signup and view all the answers

Which of the following indicates potential circulatory compromise in severe dengue?

Weak or undetectable pulse. Signup and view all the answers

What organ impairment may occur in severe cases of dengue?

Acute renal failure. Signup and view all the answers

What phenomenon occurs when antibodies from a primary infection do not neutralize a second serotype?

Antibody-Dependent Enhancement (ADE) Signup and view all the answers

What is one characteristic symptom of the condition described?

Breakbone fever Signup and view all the answers

During which phase does Herman's rash become prominent?

Convalescent or recovery phase Signup and view all the answers

What is the incubation period for the described condition?

3-7 days Signup and view all the answers

What does a positive Tourniquet test indicate?

Presence of petechiae Signup and view all the answers

Which symptom is associated with retroorbital pain?

Severe headache Signup and view all the answers

What happens during the antibody-dependent enhancement phenomenon?

Antibodies increase viral replication Signup and view all the answers

What is a significant feature of the rash described?

Macular confluence over various surfaces Signup and view all the answers

What is the average calculated from a recorded blood pressure of 120/80?

100 Signup and view all the answers

What might happen if a person experiences a second exposure to the same serotype?

More severe infection due to antibody binding Signup and view all the answers

What laboratory tests are recommended for diagnosing liver involvement in dengue?

Liver Enzymes (SGOT & SGPT) Signup and view all the answers

Which symptom is NOT considered a warning sign in dengue fever?

Leukopenia Signup and view all the answers

What indicates the need for strict observation in a dengue patient?

Liver enlargement >2cm Signup and view all the answers

What is a common laboratory finding associated with severe dengue?

Decrease in hematocrit concurrent with rapid decrease in platelet count Signup and view all the answers

Which condition is classified as severe dengue?

Severe plasma leakage leading to shock Signup and view all the answers

What is the purpose of the tourniquet test in dengue assessment?

To determine hemorrhagic tendency Signup and view all the answers

Which symptom is associated with severe organ involvement in dengue?

Severe liver enzyme elevation (AST or ALT ≥ 1000) Signup and view all the answers

In the classification of dengue, which condition requires laboratory confirmation?

Laboratory-confirmed dengue Signup and view all the answers

Which of the following symptoms is NOT listed as commonly associated with dengue fever?

Skin lesions Signup and view all the answers

What constitutes a probable dengue diagnosis?

Fever and any two of the specified symptoms Signup and view all the answers

Study Notes

Dengue Fever

Dengue is caused by a virus belonging to the Flaviviridae family, with four distinct serotypes (DENV-1, DENV-2, DENV-3, and DENV-4). A fifth variant, DENV-5, was discovered in 2013.
All serotypes grant lifelong immunity to the specific serotype and short-term cross-immunity to other serotypes. However, some genetic variants within serotypes can be more virulent, leading to varying disease severity.
The dengue virus is spread through the bite of an infected Aedes mosquito, primarily Aedes aegypti and Aedes albopictus.
The virus undergoes a period of extrinsic incubation within the mosquito, lasting 8-10 days. Once infected, the mosquito remains infectious for life.
Dengue is most common during the rainy seasons, with a peak incidence observed in July and August.
In the Philippines, there were over 208,000 dengue cases reported in September 2024, with 7 deaths.
Global estimates indicate over 200 million dengue cases and 500 dengue-related deaths annually.

Dengue Virus Transmission and Pathogenesis:

The mosquito's saliva contains anticoagulants, preventing blood clotting and facilitating efficient blood feeding.
The incubation period for dengue in a human is typically 4-7 days after the bite of an infected mosquito.
The Antibody-Dependent Enhancement (ADE) phenomenon is a key factor in severe dengue, characterized by pre-existing antibodies from a previous infection failing to neutralize the virus. This results in an increased viral load, potentially leading to dengue hemorrhagic fever (DHF) or dengue shock syndrome (DSS).
ADE occurs when antibodies from a previous infection bind to a different serotype but fail to neutralize it. This complex can attach to Fc receptors on monocytes, leading to more efficient viral entry into monocytes and macrophages.

Dengue Signs and Symptoms:

Classic Dengue:
- Fever, often biphasic in nature, lasting 2-7 days.
- Severe headache.
- Retro-orbital pain (pain behind the eyes).
- Nausea and vomiting.
- Maculopapular or macular rash, often appearing during the convalescent phase and often described as "white islands in a sea of red."
- Positive Tourniquet test, indicating capillary fragility and potential for bleeding (≥10 petechiae per 2.5 cm²).
Severe Dengue: Presence of warning signs is crucial for diagnosis and treatment.
- Plasma Leakage: Increased hematocrit, pleural effusions, ascites, circulatory compromise, and shock.
- Bleeding: Epistaxis, gingival bleeding, bleeding from injection sites.
- Organ Involvement: Liver impairment (elevated AST/ALT >/= 1000), acute renal failure, encephalopathy, CNS impairment, and cardiomyopathy.

Dengue Classification and Diagnosis:

WHO Dengue Case Classification:
- Probable Dengue: Fever plus two of the following: nausea/vomiting, rash, aches/pains, positive tourniquet test, leukopenia, or any warning signs.
- Warning Signs: Abdominal pain/tenderness, persistent vomiting, fluid accumulation, mucosal bleeding, lethargy/restlessness, liver enlargement >2 cm, rapid decrease in platelet count with increasing hematocrit.
- Severe Dengue: Severe plasma leakage, bleeding, organ involvement.
Specimen Collection: Blood samples are essential for laboratory confirmation, detecting dengue virus RNA, and monitoring platelet and hematocrit levels.

Key Diagnostic Tools:

Tourniquet Test (Capillary Fragility Test):
- Evaluates hemorrhagic tendencies.
- A positive result indicates thrombocytopenia and increased capillary fragility.
- More likely to be positive during the defervescence phase.

Dengue Hemorrhagic Fever:

Also known as "Dengue Viral Illness with Warning Signs."
Characterized by biphasic fever, hemorrhagic manifestations, and warning signs mentioned above.

Management and Prevention:

Management:
- Supportive care, fluid replacement, and close monitoring.
- Early recognition and management of warning signs are essential for preventing complications.
Prevention:
- Mosquito control measures: eliminating mosquito breeding grounds, wearing protective clothing, using mosquito repellents.
- Vaccination: Several dengue vaccines are available, offering protection against various serotypes.

Epidemiology:

Dengue is a major public health problem, particularly in tropical and subtropical regions.
Global incidence, morbidity, and mortality are increasing.
Outbreaks occur seasonally, especially during monsoon or rainy seasons.

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Description

This quiz explores the key aspects of dengue fever, including its causes, transmission, and global statistics. Learn about the dengue virus serotypes and their implications for immunity. It also highlights the impact of seasonal changes on dengue incidence and provides insight into its spread through mosquito vectors.