Virology — MCQs
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Which of the following statements is FALSE regarding Negri bodies?
Which of the Hepatitis B Virus serological markers indicates the earliest evidence of Hepatitis B infection?
Which virus can cause hemorrhage?
A 35-year-old man developed headache, nausea, vomiting, and sore throat 8 weeks after returning from a trip abroad. He eventually refused to drink water and had episodes of profuse salivation, difficulty in breathing, and hallucinations. Two days after the patient died of cardiac arrest, it was learned that he had been bitten by a dog while on his trip. Which of the following treatments, if given immediately after the dog bite, could have helped prevent this disease?
Ribavirin, a synthetic nucleoside structurally related to guanosine, has been successfully used in therapy against which of the following viruses?
Colorado tick fever is the only known human infection caused by which of the following?
Miyagawa body is characteristically seen in which of the following conditions?
A 32-year-old man presents to the emergency room with a severe headache. Nuchal rigidity is found on physical examination. Lumbar puncture demonstrates cerebrospinal fluid with markedly increased lymphocytes and no other increased cell populations. Which of the following agents is the most likely cause of his symptoms?
Which virus spreads by both hematogenous and neural routes?
Which virus is a common cause of diarrheal diseases in infants?
Virology Indian Medical PG Practice Questions and MCQs
Question 1161: Which of the following statements is FALSE regarding Negri bodies?
- A. They are pathognomonic of rabies.
- B. They are found in the brain.
- C. They are cytoplasmic inclusion bodies.
- D. They contain rabies virus antigen. (Correct Answer)
Explanation: ### Explanation The correct answer is **D**, as the statement "They contain rabies virus antigen" is technically **FALSE** in the context of classic histopathology definitions. **1. Why Option D is the Correct Answer (The False Statement):** While Negri bodies are associated with Rabies, they are primarily composed of a **matrix of viral proteins** (specifically the N and P proteins) and cellular components, rather than the infectious virions or the specific "antigen" in the way diagnostic tests (like Direct Fluorescent Antibody - DFA) detect them. In modern pathology, the DFA test detects viral antigens in the brain tissue *outside* of Negri bodies more reliably than within them. Furthermore, Negri bodies are absent in about 20-30% of confirmed rabies cases, making the detection of the antigen via DFA the "gold standard" rather than the presence of the body itself. **2. Analysis of Incorrect Options (True Statements):** * **Option A:** Negri bodies are considered **pathognomonic** for Rabies. If they are seen, the diagnosis is certain, though their absence does not rule it out. * **Option B:** They are found in the **brain**, specifically showing a predilection for the **Hippocampus (Ammon’s horn)** and the **Purkinje cells of the cerebellum**. * **Option C:** They are classic **intracytoplasmic**, eosinophilic, round-to-oval inclusion bodies. **3. NEET-PG High-Yield Clinical Pearls:** * **Stain used:** Sellers stain (basic fuchsin and methylene blue) is the traditional method to visualize them (appearing magenta with blue granules). * **Shape:** They often contain "Inner bodies" or granules (Internal bodies of Lentz). * **Fixed vs. Street Virus:** Negri bodies are produced by the **Street virus** (natural infection) but are usually absent in infections caused by the **Fixed virus** (laboratory-adapted strains used for vaccines). * **Gold Standard Diagnosis:** The Direct Fluorescent Antibody (DFA) test on brain tissue or skin biopsy (nuchal skin) is the diagnostic method of choice.
Question 1162: Which of the Hepatitis B Virus serological markers indicates the earliest evidence of Hepatitis B infection?
- A. Anti-HBs
- B. Anti-HBc
- C. HBeAg
- D. HBsAg (Correct Answer)
Explanation: ### Explanation **Correct Option: D. HBsAg** Hepatitis B Surface Antigen (HBsAg) is the **first serological marker** to appear in the blood after infection. It typically becomes detectable 2 to 8 weeks before the onset of clinical symptoms and biochemical evidence (elevated ALT/AST). Its presence indicates that the individual is currently infected (either acute or chronic) and is potentially infectious. **Analysis of Incorrect Options:** * **A. Anti-HBs:** This antibody appears only after the disappearance of HBsAg or following successful vaccination. It signifies **immunity** and recovery, appearing much later in the disease course. * **B. Anti-HBc:** This is the first **antibody** to appear (specifically the IgM isotype). While it is an early marker of the host's immune response, it appears after HBsAg has already been circulating. * **C. HBeAg:** This marker indicates active viral replication and high infectivity. While it appears early, it usually surfaces shortly **after** HBsAg. **NEET-PG High-Yield Pearls:** * **Window Period:** The interval during which HBsAg has disappeared but Anti-HBs has not yet appeared. During this phase, **IgM Anti-HBc** is the only diagnostic marker of acute infection. * **Chronic Infection:** Defined by the persistence of HBsAg in the serum for **more than 6 months**. * **Infectivity Marker:** HBeAg and HBV-DNA levels are the best indicators of high viral load and transmissibility. * **Vaccination:** A person vaccinated against HBV will be positive for **Anti-HBs only** (negative for Anti-HBc).
Question 1163: Which virus can cause hemorrhage?
- A. Parvovirus
- B. Adenovirus (Correct Answer)
- C. HPV
- D. Coronavirus
Explanation: **Explanation:** The correct answer is **Adenovirus**. Adenovirus is a double-stranded DNA virus known for its diverse tissue tropism. Specifically, **Adenovirus serotypes 11 and 21** are the most common causes of **Acute Hemorrhagic Cystitis**, a condition characterized by sudden onset hematuria (blood in urine), dysuria, and frequency, primarily seen in children (more common in boys) and immunocompromised patients. **Analysis of Options:** * **Adenovirus (Correct):** Beyond respiratory infections and conjunctivitis (Pink eye), it is a classic cause of viral-induced hemorrhage in the urinary bladder mucosa. * **Parvovirus (Incorrect):** Parvovirus B19 primarily targets erythrocyte precursors in the bone marrow. It causes Erythema Infectiosum (Fifth disease), aplastic crisis in sickle cell patients, and hydrops fetalis, but is not typically associated with hemorrhage. * **HPV (Incorrect):** Human Papillomavirus is associated with benign warts and mucosal malignancies (Cervical/Anal cancer) via epithelial proliferation, not acute hemorrhagic manifestations. * **Coronavirus (Incorrect):** While severe COVID-19 can lead to coagulopathies and microvascular thrombosis, the virus itself is not a primary cause of direct tissue hemorrhage in the same clinical context as Adenovirus. **High-Yield Clinical Pearls for NEET-PG:** * **Hemorrhagic Cystitis:** If the question specifies a post-transplant patient, consider **BK Virus** (Polyomavirus) or Adenovirus. * **Pharyngoconjunctival Fever:** Caused by Adenovirus serotypes 3 and 7 (Triad: Fever, Pharyngitis, Conjunctivitis). * **Epidemic Keratoconjunctivitis (Shipyard eye):** Caused by Adenovirus serotypes 8, 19, and 37. * **Intussusception:** Adenovirus is a known trigger for lymphoid hyperplasia (Peyer's patches), leading to intussusception in children.
Question 1164: A 35-year-old man developed headache, nausea, vomiting, and sore throat 8 weeks after returning from a trip abroad. He eventually refused to drink water and had episodes of profuse salivation, difficulty in breathing, and hallucinations. Two days after the patient died of cardiac arrest, it was learned that he had been bitten by a dog while on his trip. Which of the following treatments, if given immediately after the dog bite, could have helped prevent this disease?
- A. Broad-spectrum antibiotics
- B. High-dose acyclovir
- C. IV ribavirin
- D. Rabies immune globulin plus rabies vaccine (Correct Answer)
Explanation: ### Explanation **Correct Answer: D. Rabies immune globulin plus rabies vaccine** **Concept:** The clinical presentation—hydrophobia (refusal to drink water), aerophobia (difficulty breathing), hypersalivation, and hallucinations following a dog bite—is pathognomonic for **Rabies**, caused by the Lyssavirus. Rabies has a variable incubation period (typically 1–3 months) because the virus must travel via retrograde axonal transport from the peripheral nerves to the CNS. Once symptoms appear, the disease is almost 100% fatal. Therefore, **Post-Exposure Prophylaxis (PEP)** is the only life-saving intervention. According to WHO and National guidelines, PEP for Category III bites (transdermal bites/scratches) involves: 1. **Passive Immunization:** Rabies Immune Globulin (RIG) provides immediate neutralizing antibodies at the site. 2. **Active Immunization:** Rabies vaccine (Modern Cell Culture Vaccines) stimulates the patient’s immune system to produce antibodies before the virus reaches the CNS. **Why Incorrect Options are Wrong:** * **A. Broad-spectrum antibiotics:** These treat bacterial infections (e.g., *Pasteurella multocida*) but have no effect on the Rabies virus. * **B & C. Acyclovir and Ribavirin:** Acyclovir is specific for Herpesviruses (inhibits DNA polymerase), and Ribavirin is used for RNA viruses like HCV or RSV. Neither is effective against the Rhabdoviridae family. **High-Yield Clinical Pearls for NEET-PG:** * **Negri Bodies:** Intracytoplasmic eosinophilic inclusions found in pyramidal cells of the hippocampus and Purkinje cells of the cerebellum (Post-mortem diagnosis). * **Street Virus vs. Fixed Virus:** Street virus is the natural isolate; Fixed virus (Pasteur's) is used for vaccine production due to its short, stable incubation period. * **Site of RIG:** RIG should be infiltrated **in and around the wound**; any remainder is given IM at a site distant from the vaccine. * **Rule of Thumb:** Never suture a rabies-suspect wound immediately; if necessary, do it after 24–48 hours under RIG cover.
Question 1165: Ribavirin, a synthetic nucleoside structurally related to guanosine, has been successfully used in therapy against which of the following viruses?
- A. Respiratory syncytial virus (Correct Answer)
- B. Herpes simplex virus
- C. Hepatitis B virus
- D. Group A coxsackievirus
Explanation: **Explanation:** **Ribavirin** is a synthetic guanosine analogue that exerts its antiviral effect by interfering with the replication of viral RNA. It inhibits the enzyme **IMP dehydrogenase**, leading to the depletion of intracellular GTP pools, and interferes with the capping of viral mRNA. 1. **Why Option A is Correct:** Ribavirin is primarily indicated for the treatment of **Respiratory Syncytial Virus (RSV)** infections, particularly in severe cases involving hospitalized infants and children. It is administered via a small-particle aerosol (nebulized form). It is also used orally in combination with Interferon-alpha for **Hepatitis C** (Genotype 1 and 4) and is the drug of choice for **Lassa fever**. 2. **Why Other Options are Incorrect:** * **B. Herpes simplex virus:** Treated with **Acyclovir**, Valacyclovir, or Famciclovir, which are deoxyguanosine analogues that specifically inhibit viral DNA polymerase. * **C. Hepatitis B virus:** Managed with reverse transcriptase inhibitors like **Entecavir** or **Tenofovir**, or Interferon-alpha. Ribavirin has no significant activity against HBV. * **D. Group A coxsackievirus:** There is currently no specific FDA-approved antiviral therapy for Coxsackievirus; management is primarily supportive. **High-Yield Clinical Pearls for NEET-PG:** * **Teratogenicity:** Ribavirin is strictly contraindicated in pregnancy (Category X). Both male and female patients must use contraception for 6 months after treatment. * **Dose-dependent Hemolytic Anemia:** This is the most common and characteristic systemic side effect of oral Ribavirin. * **Spectrum:** It is a broad-spectrum antiviral effective against both DNA and RNA viruses, but its clinical utility is limited by toxicity.
Question 1166: Colorado tick fever is the only known human infection caused by which of the following?
- A. Reovirus
- B. Coltivirus (Correct Answer)
- C. Rotavirus
- D. Coronavirus
Explanation: **Explanation:** **Colorado Tick Fever (CTF)** is a viral zoonotic disease transmitted by the bite of the Rocky Mountain wood tick (*Dermacentor andersoni*). It is caused by the **Coltivirus**, which belongs to the family **Reoviridae**. 1. **Why Coltivirus is correct:** Coltiviruses are characterized by a genome consisting of 12 segments of double-stranded RNA (dsRNA). In humans, Colorado Tick Fever is the only significant clinical infection caused by this genus [1]. The virus infects erythrocyte precursor cells, allowing it to persist in the bloodstream for several weeks, protected from the immune system. 2. **Why other options are incorrect:** * **Reovirus:** While Coltivirus is in the Reoviridae family, the genus *Orthoreovirus* (often just called Reovirus) typically causes mild, often asymptomatic respiratory or gastrointestinal illnesses in humans, not CTF. * **Rotavirus:** Also a member of Reoviridae, it is the leading cause of severe dehydrating diarrhea in infants and young children worldwide, transmitted via the fecal-oral route [1]. * **Coronavirus:** These are enveloped, positive-sense single-stranded RNA viruses (family Coronaviridae) responsible for respiratory infections ranging from the common cold to SARS and COVID-19 [1]. **High-Yield Clinical Pearls for NEET-PG:** * **Vector:** *Dermacentor andersoni* (Rocky Mountain wood tick). * **Clinical Presentation:** Characterized by a **"saddleback" fever** (biphasic fever pattern), chills, headache, and myalgia. * **Diagnosis:** Suggested by leukopenia (low WBC) and confirmed by PCR or virus isolation. * **Key Distinction:** Unlike Rocky Mountain Spotted Fever (caused by *Rickettsia rickettsii*), CTF is viral and does not respond to antibiotics.
Question 1167: Miyagawa body is characteristically seen in which of the following conditions?
- A. Kala azar
- B. Syphilis
- C. Granuloma inguinale
- D. Lymphogranuloma venereum (LGV) (Correct Answer)
Explanation: **Explanation:** **Miyagawa bodies** (also known as elementary bodies) are the characteristic intracellular inclusion bodies seen in **Lymphogranuloma venereum (LGV)**, which is caused by *Chlamydia trachomatis* serotypes L1, L2, and L3. 1. **Why LGV is correct:** *Chlamydia* are obligate intracellular bacteria with a unique life cycle involving two forms: the **Elementary Body (EB)** and the **Reticulate Body (RB)**. In LGV, these EBs aggregate within the cytoplasm of infected host cells (macrophages and epithelial cells) to form large, basophilic inclusion bodies known as Miyagawa bodies. These are diagnostic when visualized under Giemsa or iodine stains. 2. **Why other options are incorrect:** * **Kala-azar (Visceral Leishmaniasis):** Characterized by **LD bodies** (Leishman-Donovan bodies), which are the amastigote stage of *Leishmania donovani* found within macrophages. * **Syphilis:** Caused by *Treponema pallidum*. It does not form inclusion bodies; diagnosis relies on dark-ground microscopy or serology (VDRL/TPHA). * **Granuloma inguinale (Donovanosis):** Caused by *Klebsiella granulomatis*. It is characterized by **Donovan bodies**, which are safety-pin shaped organisms seen within large mononuclear cells. **High-Yield Clinical Pearls for NEET-PG:** * **LGV Clinical Triad:** Primary painless vesicle, painful inguinal lymphadenopathy (**Groove sign**), and proctocolitis. * **Frei’s Test:** A delayed hypersensitivity skin test previously used for LGV (now largely replaced by NAAT). * **Halberstaedter-Prowazek bodies:** Inclusion bodies seen in *Chlamydia trachomatis* serotypes A, B, and C (Trachoma). * **Levinthal-Cole-Lillie (LCL) bodies:** Inclusion bodies seen in *Psittacosis*.
Question 1168: A 32-year-old man presents to the emergency room with a severe headache. Nuchal rigidity is found on physical examination. Lumbar puncture demonstrates cerebrospinal fluid with markedly increased lymphocytes and no other increased cell populations. Which of the following agents is the most likely cause of his symptoms?
- A. Escherichia coli
- B. Haemophilus influenzae
- C. Herpes virus (Correct Answer)
- D. Mycobacterium tuberculosis
Explanation: ### Explanation The clinical presentation of headache and nuchal rigidity indicates **meningitis**. The key to solving this case lies in the CSF analysis: **markedly increased lymphocytes** with no other cell types (like neutrophils) suggests **Aseptic (Viral) Meningitis**. **1. Why Herpes Virus is Correct:** Viral infections are the most common cause of lymphocytic pleocytosis in the CSF. While Enteroviruses are the most frequent cause of viral meningitis overall, **Herpes Simplex Virus (HSV)**—specifically HSV-2—is a significant cause of aseptic meningitis in adults. In viral meningitis, CSF typically shows normal glucose, normal to slightly elevated protein, and a predominance of lymphocytes. **2. Why the Other Options are Incorrect:** * **A. Escherichia coli & B. Haemophilus influenzae:** These are causes of **Acute Pyogenic (Bacterial) Meningitis**. The CSF profile would show a predominance of **neutrophils** (polymorphonuclear leukocytes), significantly decreased glucose, and markedly elevated protein. * **D. Mycobacterium tuberculosis:** While TB meningitis causes lymphocytic pleocytosis, it is typically associated with a **"cobweb" appearance** of CSF, very high protein levels, and **significantly decreased glucose**. The clinical course is also usually more subacute/chronic rather than an emergency presentation. **3. NEET-PG High-Yield Pearls:** * **HSV-1** is the most common cause of sporadic **Viral Encephalitis** (targeting the temporal lobes). * **HSV-2** is more commonly associated with **Viral Meningitis** (Mollaret’s meningitis). * **CSF Findings Summary:** * *Bacterial:* ↑ Neutrophils, ↓ Glucose, ↑↑ Protein. * *Viral:* ↑ Lymphocytes, Normal Glucose, Normal/↑ Protein. * *Tubercular:* ↑ Lymphocytes, ↓ Glucose, ↑ Protein (Fibrin web).
Question 1169: Which virus spreads by both hematogenous and neural routes?
- A. Rabies virus
- B. Varicella zoster virus
- C. Poliovirus (Correct Answer)
- D. Epstein-Barr virus
Explanation: ### Explanation **Correct Answer: C. Poliovirus** The spread of Poliovirus is unique because it utilizes both **hematogenous** and **neural** pathways to reach the Central Nervous System (CNS). 1. **Hematogenous Route:** After ingestion, the virus multiplies in the Peyer’s patches of the intestine and spreads to the regional lymph nodes, leading to a **primary viremia**. It then enters the bloodstream (**secondary viremia**) to reach various organs, including the CNS. 2. **Neural Route:** Poliovirus can also reach the spinal cord via **retrograde axonal transport** from peripheral nerves. This dual mechanism ensures its high neurotropism, leading to the destruction of anterior horn cells. --- ### Why the other options are incorrect: * **A. Rabies virus:** Spreads almost exclusively via the **neural route** (centripetal spread through peripheral nerves to the CNS). It does not have a significant viremic phase. * **B. Varicella Zoster Virus (VZV):** While it spreads hematogenously during primary infection (Chickenpox) and resides in sensory ganglia, its reactivation (Shingles) follows a neural path. However, in the context of initial CNS invasion mechanisms, Polio is the classic example of the dual route. * **D. Epstein-Barr Virus (EBV):** Spreads primarily through **saliva** (oropharyngeal secretions) and infects B-cells. It does not typically utilize neural pathways for spread. --- ### High-Yield Clinical Pearls for NEET-PG: * **Most common site of Polio paralysis:** Lower limbs (asymmetric flaccid paralysis). * **Specimen of choice:** Stool (virus is excreted for weeks) is more reliable than CSF for diagnosis. * **Blood-Brain Barrier (BBB):** Most neurotropic viruses cross the BBB during viremia; Polio is a rare example that bypasses it via axonal transport. * **Other viruses with dual routes:** Herpes Simplex Virus (HSV) and Measles (rarely) can also exhibit both routes, but Polio is the most frequently tested "dual route" virus in exams.
Question 1170: Which virus is a common cause of diarrheal diseases in infants?
- A. Rotavirus (Correct Answer)
- B. Norwalk virus
- C. Adenovirus
- D. Hepatadenovirus
Explanation: **Explanation:** **1. Why Rotavirus is Correct:** Rotavirus (a Reovirus) is the **most common cause of severe, dehydrating diarrhea in infants and young children (6–24 months)** worldwide. It primarily infects the mature enterocytes of the small intestine. The pathophysiology involves the **NSP4 enterotoxin**, which induces a secretory diarrhea by increasing intracellular calcium and disrupting SGLT-1 mediated glucose absorption. In the NEET-PG context, remember it follows a "winter seasonality" in temperate climates and is characterized by a "wheel-like" appearance on electron microscopy. **2. Analysis of Incorrect Options:** * **B. Norwalk virus (Norovirus):** While it is the leading cause of viral gastroenteritis outbreaks across all age groups, it is classically associated with **adults**, cruise ships, schools, and shellfish consumption. * **C. Adenovirus:** Specifically Serotypes **40 and 41** (Subgroup F) cause diarrhea in children. While significant, they are less common than Rotavirus and typically cause a more prolonged, less severe illness. * **D. Hepatadenovirus:** This is a misnomer or refers to *Hepadnaviridae* (like Hepatitis B), which affects the liver, not the gastrointestinal tract to cause diarrhea. **3. High-Yield Clinical Pearls for NEET-PG:** * **Morphology:** Double-stranded RNA (dsRNA), segmented (11 segments), non-enveloped, icosahedral. * **Diagnosis:** Latex agglutination or ELISA for VP6 antigen in stool. * **Vaccines:** Live attenuated oral vaccines (**Rotarix** - monovalent; **RotaTeq** - pentavalent) are part of the Universal Immunization Programme (UIP) in India. * **Complication:** A rare but classic association with Rotavirus vaccines is **intussusception**.
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