Infectious Diseases Practice Questions

Q: Evaluation of a specimen from a patient with hepatocellular carcinoma demonstrates the presence of a single-stranded RNA virus. Which of the following is the most probable etiological agent?

Hepatitis C virus. ### Explanation The correct answer is **Hepatitis C virus (HCV)**. **1. Why Hepatitis C is correct:** Hepatitis C is a **single-stranded RNA (ssRNA)** virus belonging to the *Flaviviridae* family. It is a major risk factor for the development of Hepatocellular Carcinoma (HCC). Unlike DNA viruses, HCV does not integrate into the host genome; instead, it promotes oncogenesis through chronic inflammation, oxidative stress, and the action of non-structural proteins (like NS5A) that interfere with cell cycle regulation and apoptosis. Active infection is confirmed by the presence of serum hepatitis C RNA [1]. **2. Why other options are incorrect:** * **Hepatitis B virus (HBV):** While HBV is a leading cause of HCC worldwide, it is a **partially double-stranded DNA virus** (*Hepadnaviridae*). It can cause HCC even without cirrhosis due to its ability to integrate into the host DNA. * **Hepatitis A (HAV) and Hepatitis E (HEV):** Both are RNA viruses transmitted via the fecal-oral route [3]. However, they cause **acute hepatitis** only and do not lead to chronic infection, cirrhosis, or an increased risk of HCC. (Note: HEV can be chronic in immunocompromised patients, but it is not typically linked to HCC). **3. High-Yield Clinical Pearls for NEET-PG:** * **Genome Type:** Remember the mnemonic "All Hepatitis viruses are RNA except **B** (DNA)." * **HCC Risk:** In the presence of cirrhosis, HCV has a higher annual risk of progressing to HCC compared to HBV. * **Screening:** Patients with chronic HCV and cirrhosis should undergo HCC surveillance every 6 months using **Ultrasonography +/- Alpha-fetoprotein (AFP)** [2]. * **Treatment:** Direct-acting antivirals (DAAs) can achieve a Sustained Virologic Response (SVR), significantly reducing but not entirely eliminating the risk of HCC.

Q: Faget's sign is seen in:

Enteric fever. **Explanation:** **Faget’s Sign** (also known as sphygmothermic dissociation) refers to the clinical finding of a **relative bradycardia** in the presence of a high fever [3]. Normally, for every 1°F rise in body temperature, the pulse rate is expected to increase by approximately 10 beats per minute (Liebermeister’s rule). In Faget’s sign, the pulse remains slow despite the rising temperature. **1. Why Enteric Fever is Correct:** In **Enteric (Typhoid) fever**, caused by *Salmonella Typhi*, relative bradycardia is a classic diagnostic clue during the first and second weeks of illness [1]. The exact mechanism is debated but is thought to involve the effect of bacterial endotoxins on the myocardium or the sinoatrial node. Around the 7th–10th day, the spleen often becomes palpable [1]. **2. Analysis of Incorrect Options:** * **Plague:** Typically presents with tachycardia due to severe systemic toxicity and potential septic shock [2]. * **Anthrax:** Characterized by rapid progression and systemic inflammatory response syndrome (SIRS), which manifests as tachycardia. * **Meningococcal Meningitis:** Usually presents with tachycardia as part of the acute febrile response and sympathetic activation due to increased intracranial pressure (unless the late-stage Cushing’s triad occurs). **3. NEET-PG High-Yield Pearls:** * **Differential Diagnosis for Faget’s Sign:** Remember the mnemonic **"LYB"** or **"Yellow Typhoid Legion"**: * **L**egionnaire’s disease * **Y**ellow fever (The original disease where Faget described the sign) * **B**rucellosis * **T**yphoid fever * **T**ularemia * **P**sittacosis * **Step-ladder fever:** The characteristic temperature pattern seen in the first week of Enteric fever. * **Rose spots:** Faint, salmon-colored macules seen on the trunk in 30% of Typhoid cases.

Q: Hemorrhagic fever of dengue is transmitted by which mosquito?

A. aegypti. **Explanation:** **Correct Answer: C. Aedes aegypti** Dengue Hemorrhagic Fever (DHF) is caused by the Dengue virus (a Flavivirus) [1], which is primarily transmitted by the **Aedes aegypti** mosquito. This mosquito is a "day-biter," typically most active during early morning and late afternoon. It breeds in clean, stagnant water found in artificial containers (coolers, flower pots, tires). While *Aedes albopictus* can also transmit the virus, *A. aegypti* remains the principal vector due to its highly anthropophilic (human-preferring) nature. **Analysis of Incorrect Options:** * **A. Mansonia:** This genus is the primary vector for **Brugian Filariasis** (*Brugia malayi*). They are unique because their larvae attach to the roots of aquatic plants (like *Pistia*) for respiration. * **B. Anopheles:** This is the well-known vector for **Malaria**. It typically bites at night and breeds in clean, moving, or still water (depending on the species). * **D. Culex:** Known as the "nuisance mosquito," it transmits **Japanese Encephalitis**, **Bancroftian Filariasis** (*Wuchereria bancrofti*), and West Nile Virus. It typically breeds in dirty, polluted water. **NEET-PG Clinical Pearls:** * **Vector Characteristics:** *A. aegypti* is often called the "Tiger Mosquito" (though this name is more accurately applied to *A. albopictus*) due to white stripes on its body. It is a "nervous feeder," biting multiple people to complete one blood meal, which leads to rapid outbreaks. * **DHF Pathogenesis:** DHF usually occurs during a **secondary infection** with a different serotype (there are 4 serotypes: DEN 1-4) due to **Antibody-Dependent Enhancement (ADE)** [1]. * **Diagnostic Marker:** **NS1 Antigen** is the gold standard for early diagnosis (Days 1–5); **IgM ELISA** is used after Day 5. Signs of DHF or Dengue Shock Syndrome (DSS) typically develop during the 'critical phase', 3–7 days after fever onset [1].

Q: Which of the following statements about hepatitis G virus is false?

It responds to lamivudine therapy.. **Explanation:** The Hepatitis G Virus (HGV), also known as **GB virus C (GBV-C)**, is a member of the *Flaviviridae* family. The correct answer is **D** because HGV is an **RNA virus**, and **Lamivudine** is a nucleoside analog that inhibits reverse transcriptase, primarily used for DNA viruses like Hepatitis B (HBV) or retroviruses like HIV. It has no therapeutic role in HGV infection. **Analysis of Options:** * **Option A:** HGV was independently discovered and named GB virus C (after surgeon G. Barker). Both terms are used interchangeably in medical literature. * **Option B:** It is a positive-sense, single-stranded **RNA virus**. Its primary mode of transmission is parenteral (blood-borne), similar to HCV and HBV. * **Option C:** Due to shared transmission routes (IV drug use, blood transfusions), HGV is frequently found as a co-infection with **HCV** (up to 10-20% of cases) and HIV. **High-Yield Clinical Pearls for NEET-PG:** 1. **Pathogenicity:** Despite its name, HGV is generally considered **non-pathogenic**. It does not cause acute or chronic hepatitis, nor does it worsen the clinical course of HCV or HBV. 2. **HIV Benefit:** A high-yield fact is that HGV/GBV-C co-infection in **HIV patients** is associated with **slower disease progression** and improved survival rates, possibly due to interference with HIV entry into CD4 cells. 3. **Diagnosis:** It is diagnosed via **RT-PCR** for HGV RNA; there is no routine serological test used in clinical practice.

Question 1

A patient tested positive for MTB on sputum CBNAAT. The patient did not return to the PHC despite multiple reminders. The patient now presents with non-massive hemoptysis and is alarmed. What is the next best step for this patient?

Accepted Answer

Perform CT scan of the chest

Answer

Urgent coagulation studies

Answer

Schedule a flexible fibreoptic bronchoscopy

Answer

Urgent rigid bronchoscopy with prophylactic balloon tamponade

Question 2

Severity in acute hepatitis is best estimated by?

Accepted Answer

Alkaline phosphatase

Answer

Serum bilirubin

Answer

Prothrombin time (PT)

Answer

Alpha-1-antitrypsin

Question 3

An 18-year-old, previously healthy female presents with fever, vomiting, diarrhea, hypotension, and an erythematous, red, sunburn-like skin rash. She is currently menstruating and using super-absorbent tampons. Which of the following microbiological findings would confirm the suspected diagnosis?

Accepted Answer

Organisms are coagulase positive

Answer

Organisms are acid-fast

Answer

Organisms grow on EMB agar

Answer

Organisms grow on Thayer-Martin media

Question 4

Evaluation of a specimen from a patient with hepatocellular carcinoma demonstrates the presence of a single-stranded RNA virus. Which of the following is the most probable etiological agent?

Accepted Answer

Hepatitis C virus

Answer

Hepatitis A virus

Answer

Hepatitis B virus

Answer

Hepatitis E virus

Question 5

Faget's sign is seen in:

Accepted Answer

Enteric fever

Answer

Plague

Answer

Anthrax

Answer

Meningococcal meningitis

Question 6

Hemorrhagic fever of dengue is transmitted by which mosquito?

Accepted Answer

A. aegypti

Answer

Mansonia

Answer

Anopheles

Answer

Culex

Question 7

An active intravenous drug abuser presents with a 5-day history of fever, a cough occasionally productive of blood, and pleuritic chest pain. Petechiae are present in his mouth and conjunctiva, and small linear hemorrhages are visible under his fingernails. Which of the following test results would MOST likely confirm the identity of the causative agent?

Accepted Answer

Blood culture of a coagulase-positive, catalase positive, gram-positive coccus

Answer

Antibodies to p24 capsid antigen

Answer

Antibodies to Trichinella spiralis antigen

Answer

Blood culture of a catalase-positive, novobiocin-sensitive, gram-positive coccus

Question 8

What is the most likely diagnosis in a patient with a migratory, pruritic skin eruption?

Accepted Answer

Cutaneous larva migrans

Answer

Contact dermatitis

Answer

Paragonimiasis

Answer

Myiasis

Question 9

Which of the following statements about hepatitis G virus is false?

Accepted Answer

It responds to lamivudine therapy.

Answer

It is also called GB virus.

Answer

It is a blood-borne RNA virus.

Answer

It is mostly found co-infecting with hepatitis C virus.

Question 10

Which feature would most likely be found in a patient with lepromatous leprosy?

Accepted Answer

Macrophages with a foamy appearance in the dermis

Answer

Absence of bacteremia

Answer

A positive lepromin reaction

Answer

A high cell-mediated response against Mycobacterium leprae

Infectious Diseases — MCQs

Infectious Diseases — MCQs

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