Dengue and Other Viral Hemorrhagic Fevers — MCQs
Patient: fever, joint pain, rash. Recent history of mosquito bite. Most likely diagnosis in urban area?
Which of the following statements regarding dengue fever is false?
Which of the following statements regarding classical Dengue fever is FALSE?
A previously healthy child has sudden onset of red spots on body. There is a history of a preceding viral infection 1-4 weeks before the onset.
Dengue hemorrhagic fever on Day 5: Which investigation is most appropriate?
A patient hailing from Delhi presents with fever, arthralgia, and extensive petechial rash for 3 days. Lab investigations revealed a hemoglobin of 9 g/ dL, a white blood cell count of 9000 cells/mm3, a platelet count of 20000 cells/mm3, and a prolonged bleeding time. The clotting time was normal. What is the most likely diagnosis?
Dengue haemorrhagic fever is diagnosed by-
A patient presents with fever and retro-orbital pain. Which investigation should be conducted next for confirmation of dengue fever?
Which is the main vector of Dengue?
What is the most likely diagnosis for a patient presenting with sudden onset headache and neck rigidity?
Dengue and Other Viral Hemorrhagic Fevers Indian Medical PG Practice Questions and MCQs
Question 1: Patient: fever, joint pain, rash. Recent history of mosquito bite. Most likely diagnosis in urban area?
- A. Dengue
- B. Japanese Encephalitis
- C. Malaria
- D. Chikungunya (Correct Answer)
Explanation: ***Chikungunya*** - **Chikungunya** is a viral disease transmitted by mosquitoes that commonly presents with **fever**, severe **joint pain** (polyarthralgia), and a **rash**, fitting the patient's symptoms. - Its high prevalence in **urban areas** and recent history of **mosquito bites** make it a strong diagnostic consideration. *Dengue* - While Dengue also causes **fever** [1] and a **rash**, it is more typically associated with **severe muscle and bone pain** ("breakbone fever"), and **hemorrhagic manifestations** or shock, which are not mentioned. - **Joint pain** in dengue is usually less debilitating than in chikungunya. *Japanese Encephalitis* - This is a serious **neurological infection** characterized by **fever**, **headache**, seizures, and altered mental status, rather than prominent joint pain and rash. - It primarily affects the **brain** and is less likely to present with this specific symptom triad. *Malaria* - Malaria is characterized by **cyclic fevers**, chills, sweating, and fatigue, but typically **does not present with a rash** [1] or significant joint pain. - It is caused by a **parasite** transmitted by *Anopheles* mosquitoes, and its clinical picture differs from the described symptoms.
Question 2: Which of the following statements regarding dengue fever is false?
- A. Common in south Asian region
- B. Transmitted by Aedes aegypti
- C. Thrombocytopenia
- D. Subclinical cases never occur (Correct Answer)
Explanation: **Subclinical cases never occur** - This statement is false because **subclinical** or **asymptomatic infections** are common in dengue fever, meaning many infected individuals do not develop noticeable symptoms but can still transmit the virus. - Studies indicate that the ratio of asymptomatic to symptomatic cases can be as high as 4:1, playing a significant role in **virus transmission** and **herd immunity**. *Common in south Asian region* - This statement is true; **dengue fever** is highly **endemic** in South Asian regions, including countries like India, Bangladesh, and Pakistan, due to suitable climatic conditions for the **Aedes mosquito** and high population density. - The region experiences annual outbreaks, particularly during **monsoon seasons**, leading to a substantial public health burden. *Transmitted by Aedes aegypti* - This statement is true. Dengue fever is primarily transmitted to humans through the bite of infected female **Aedes aegypti mosquitoes**. - **Aedes albopictus** can also act as a vector, but **Aedes aegypti** is considered the main vector in most urban areas. *Thrombocytopenia* - This statement is true. **Thrombocytopenia** (low platelet count) is a hallmark of dengue fever, often correlating with disease severity and risk of **hemorrhage**. - As platelet counts drop, patients are at higher risk of **bleeding complications**, especially in **severe dengue**.
Question 3: Which of the following statements regarding classical Dengue fever is FALSE?
- A. Positive tourniquet test (Correct Answer)
- B. Low case fatality rate
- C. Self limiting disease
- D. Transmitted by Aedes aegypti
Explanation: **CRITICAL ISSUE:** This question as currently written is problematic because **all four statements are TRUE** about classical dengue fever, making it impossible to identify a FALSE statement. ***Analysis of Each Statement:*** **Positive tourniquet test** (Currently marked as answer) - This is actually a **TRUE statement** about classical dengue fever - The tourniquet test is **positive in classical dengue fever** and is used as a diagnostic criterion by WHO - A positive tourniquet test indicates capillary fragility and is seen in both classical dengue and DHF - **This should NOT be the answer** to a FALSE question **Low case fatality rate** - TRUE statement: Classical dengue fever has a very low case fatality rate (<1%) with proper supportive care - Mortality is primarily associated with severe dengue/DHF/DSS **Self limiting disease** - TRUE statement: Classical dengue is typically self-limiting, resolving within 7-10 days with symptomatic treatment - Characterized by fever, headache, retro-orbital pain, myalgia, and rash **Transmitted by Aedes aegypti** - TRUE statement: **Aedes aegypti** is the primary vector for dengue transmission - Also transmitted by Aedes albopictus in some regions - Day-biting mosquitoes found in urban/semi-urban areas **RECOMMENDATION:** This question needs revision as it currently has no correct answer. All options are true statements about classical dengue fever.
Question 4: A previously healthy child has sudden onset of red spots on body. There is a history of a preceding viral infection 1-4 weeks before the onset.
- A. Dengue fever
- B. Hemophilia A
- C. Idiopathic thrombocytopenic purpura (Correct Answer)
- D. Thrombotic thrombocytopenic purpura
Explanation: ***Idiopathic thrombocytopenic purpura (ITP)*** - This presentation, especially in a previously healthy child with a preceding viral infection 1-4 weeks prior, is highly characteristic of **acute ITP**, leading to **purpuric rash** (red spots). - The preceding viral infection often triggers an autoimmune response causing destruction of **platelets**, resulting in **thrombocytopenia**. *Dengue fever* - Dengue fever typically presents with **acute onset of fever**, **headache**, **myalgia**, and a rash that appears 3-4 days after fever onset, often with a shorter incubation period than 1-4 weeks. - While it can cause petechiae due to **thrombocytopenia**, the symptom constellation does not perfectly align with the scenario, particularly the sudden onset of spots without mention of fever or other acute symptoms. *Hemophilia A* - **Hemophilia A** is a **hereditary bleeding disorder** causing deficits in **Factor VIII**, leading to spontaneous bleeding into joints and muscles, and prolonged bleeding after trauma. - It does not present as sudden onset red spots (petechiae/purpura) following a viral infection but rather as larger **hematomas** or **hemarthroses**, and it's a chronic condition, not typically triggered by recent infection. *Thrombotic thrombocytopenic purpura (TTP)* - TTP is characterized by the **pentad of symptoms**: **fever**, **neurological symptoms**, **renal dysfunction**, **microangiopathic hemolytic anemia**, and **thrombocytopenia**. - While it involves thrombocytopenia and can cause purpura, the patient's presentation lacks the other severe systemic features typically associated with TTP, and it's less commonly triggered by a simple viral infection in children.
Question 5: Dengue hemorrhagic fever on Day 5: Which investigation is most appropriate?
- A. RT PCR
- B. Viral culture
- C. IgM ELISA (Correct Answer)
- D. NS1 Antigen
Explanation: ***IgM ELISA*** - From day 4-5 onwards in dengue infection, **IgM antibodies** start to become detectable and their levels rise significantly towards the end of the first week and into the second week. - An **IgM ELISA** (Enzyme-Linked Immunosorbent Assay) is a highly sensitive and specific method for detecting these antibodies, making it the most appropriate test on Day 5. *RT PCR* - **Reverse transcriptase polymerase chain reaction (RT-PCR)** detects viral RNA and is most useful in the early stages of dengue infection (first 1-5 days) when viremia is high. - By Day 5, viral load may be decreasing, making RT-PCR less sensitive compared to antibody detection. *Viral culture* - **Viral culture** is generally labor-intensive, time-consuming, and has low sensitivity for dengue virus detection in clinical practice. - It is not commonly used for routine diagnosis and is usually reserved for research purposes. *NS1 Antigen* - **NS1 antigen** detection is most useful in the very early acute phase of dengue infection, typically within the first 0-5 days. - While it might still be detectable on Day 5, its sensitivity tends to decrease after the first few days, whereas IgM antibodies are increasing, making IgM ELISA a better choice for that time point [1]. *Clinical Course* - The period 3–7 days after onset of fever is termed the ‘critical’ phase, during which signs of Dengue Hemorrhagic Fever (DHF) may develop [1].
Question 6: A patient hailing from Delhi presents with fever, arthralgia, and extensive petechial rash for 3 days. Lab investigations revealed a hemoglobin of 9 g/ dL, a white blood cell count of 9000 cells/mm3, a platelet count of 20000 cells/mm3, and a prolonged bleeding time. The clotting time was normal. What is the most likely diagnosis?
- A. Dengue (Correct Answer)
- B. Malaria
- C. Scrub typhus
- D. Typhoid
Explanation: Dengue - The combination of **fever, arthralgia, extensive petechial rash**, and severe **thrombocytopenia** (platelet count 20,000/mm³) with **prolonged bleeding time** is highly characteristic of severe dengue infection, especially in an endemic area like Delhi [1]. - While leukocytosis (WBC 9000/mm³) is not typical for dengue (usually causes leukopenia), the other features strongly point to dengue hemorrhagic fever [1]. *Malaria* - Typically presents with **intermittent high fever**, chills, and sweats. While it can cause some thrombocytopenia and anemia, the **extensive petechial rash** is not a characteristic feature. - **Thrombocytopenia** in malaria is usually milder than observed here, and prolonged bleeding time is less common [2]. *Scrub typhus* - Caused by Orientia tsutsugamushi, it is characterized by **fever, headache, myalgia, and a characteristic eschar** (necrotic ulcer) at the bite site, which is not mentioned. - While it can cause rash and some thrombocytopenia, the **petechial rash** and such severe thrombocytopenia with prolonged bleeding time are less typical. *Typhoid* - Presents with **sustained high fever**, headache, bradycardia, and sometimes a **rose spot rash** (maculopapular), which is different from a petechial rash. - Typhoid typically causes **leukopenia** and can lead to gastrointestinal complications like intestinal bleeding, but severe thrombocytopenia and extensive petechiae are not common presenting features.
Question 7: Dengue haemorrhagic fever is diagnosed by-
- A. Acute onset of high fever, positive tourniquet test, epistaxis or melena, and platelet count > 150,000/µL
- B. Acute onset of high fever, positive tourniquet test, bleeding gum and platelet count < 100,000/µL (Correct Answer)
- C. Acute onset of high fever, presence of petechiae, epistaxis and platelet count > 200,000/µL
- D. Acute onset of high fever (2-7 days), hemorrhagic manifestation (e.g., hemoptysis), and platelet count < 150,000/µL
Explanation: Dengue haemorrhagic fever is diagnosed by- ***Acute onset of high fever, positive tourniquet test, bleeding gum, and platelet count < 100,000/µL*** - **Dengue hemorrhagic fever (DHF)** is characterized by **acute high fever**, evidence of **plasma leakage**, and **hemorrhagic manifestations** such as **bleeding gums**, along with significant **thrombocytopenia** (platelet count < 100,000/µL) [1]. - A **positive tourniquet test** indicates increased capillary fragility, which is a hallmark of dengue-induced vascular permeability [1]. *Acute onset of high fever, positive tourniquet test, epistaxis or melena, and platelet count > 150,000/µL* - While **acute high fever**, **positive tourniquet test**, **epistaxis**, or **melena** can be present in DHF, a **platelet count > 150,000/µL** is contrary to the diagnostic criteria for DHF. - DHF requires significant **thrombocytopenia** (platelet count < 100,000/µL) due to bone marrow suppression and peripheral destruction. *Acute onset of high fever, presence of petechiae, epistaxis, and platelet count > 200,000/µL* - The presence of **acute high fever**, **petechiae**, and **epistaxis** are consistent with DHF symptoms, indicating bleeding tendencies [1]. - However, a **platelet count > 200,000/µL** contradicts the diagnostic criteria for DHF, which mandates **thrombocytopenia** (<100,000/µL). *Acute onset of high fever (2-7 days), hemorrhagic manifestation (e.g., hemoptysis), and platelet count < 150,000/µL* - **Acute high fever** and **hemorrhagic manifestations** like **hemoptysis** (though less common than other forms of bleeding) are features of DHF. - However, while **platelet count < 150,000/µL** indicates thrombocytopenia, the specific diagnostic threshold for DHF is typically **< 100,000/µL**.
Question 8: A patient presents with fever and retro-orbital pain. Which investigation should be conducted next for confirmation of dengue fever?
- A. Viral culture
- B. NS1 antigen test (Correct Answer)
- C. IgM ELISA
- D. PCR
Explanation: ***NS1 antigen test*** - The **NS1 antigen test** is highly sensitive and specific for dengue in the **early stages** of infection (typically 0-7 days after symptom onset), which is when a patient with fever and retro-orbital pain would likely present. - It detects a non-structural protein of the dengue virus, indicating **active viral replication**. *Viral culture* - **Viral culture** for dengue is time-consuming and technically demanding, making it impractical for rapid diagnosis in clinical settings, especially when an urgent confirmation is needed for patient management. - It is primarily used for research purposes rather than routine clinical diagnosis [2]. *IgM ELISA* - **IgM ELISA** detects antibodies produced in response to dengue infection, which typically become detectable **5-7 days after symptom onset**. - While useful for confirming dengue in later stages of illness, it may yield a **false negative** result if performed too early in the course of the disease [2]. *PCR* - **PCR (Polymerase Chain Reaction)** detects dengue viral RNA and is highly sensitive and specific in the **early acute phase** of infection (first 5 days) [1]. - However, it is generally more expensive, requires specialized laboratory equipment, and has a longer turnaround time compared to the NS1 antigen test, making NS1 a more accessible initial diagnostic choice.
Question 9: Which is the main vector of Dengue?
- A. A. aegypti (Correct Answer)
- B. Culex
- C. Anopheles
- D. Aedes scutellaris
Explanation: ***A. aegypti*** - **Aedes aegypti** is the primary vector responsible for transmitting the **Dengue virus** to humans. - It is a **day-biting mosquito** found predominantly in tropical and subtropical regions. *Culex* - **Culex mosquitoes** are known vectors for diseases like **Japanese encephalitis**, **West Nile virus**, and **filariasis**. - They are generally **night-biting** and do not play a significant role in Dengue transmission. *Anopheles* - **Anopheles mosquitoes** are the primary vectors for **malaria** in humans. - They are not associated with the transmission of the Dengue virus. *Aedes scutellaris* - While part of the **Aedes genus**, **Aedes scutellaris** is a secondary vector for Dengue in the **Pacific region**. - The main vector for Dengue globally remains **Aedes aegypti**, followed by **Aedes albopictus** in some regions.
Question 10: What is the most likely diagnosis for a patient presenting with sudden onset headache and neck rigidity?
- A. Intraparenchymal hemorrhage
- B. Meningitis
- C. Subarachnoid Hemorrhage (Correct Answer)
- D. None of the options
Explanation: ***Subarachnoid Hemorrhage*** - A **sudden onset headache**, often described as the **"worst headache of my life,"** [1] combined with **neck rigidity (nuchal rigidity)**, [1] is highly characteristic of a subarachnoid hemorrhage. - This condition results from bleeding into the **subarachnoid space**, typically due to a ruptured aneurysm, [2] leading to meningeal irritation. *Intraparenchymal hemorrhage* - While an intraparenchymal hemorrhage can cause a sudden headache, **neck rigidity** is less common unless the hemorrhage is very large or extends into the ventricular system, irritating the meninges. - Neurological deficits are often more prominent and specific to the affected brain region, such as **hemiparesis** or **aphasia**. *Meningitis* - Meningitis also presents with **headache** and **neck rigidity**, [1] but the onset is usually more gradual, developing over hours to days, unlike the abrupt onset seen in this case. - Additionally, fever, photophobia, and altered mental status are common accompanying symptoms in meningitis. *None of the options* - This option is incorrect because **subarachnoid hemorrhage** is a strong and plausible diagnosis given the presented symptoms.
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