Virology — MCQs

Virology Indian Medical PG Practice Questions and MCQs

Question 631: All of the following are components of Dane particles except?

A. Surface antigen
B. Core antigen
C. C-antigen
D. Delta antigen (Correct Answer)

Explanation: **Explanation:** The **Dane particle** represents the complete, infectious virion of the **Hepatitis B Virus (HBV)**. It is a 42 nm spherical structure consisting of an inner core and an outer envelope. **Why Delta Antigen is the correct answer:** The **Delta antigen (HDAg)** is a component of the **Hepatitis D Virus (HDV)**, not HBV. While HDV is a "defective" virus that requires the presence of HBV (specifically HBsAg) to provide its outer envelope for assembly and transmission, the Delta antigen itself is part of the HDV ribonucleoprotein complex, not a structural component of the Dane particle. **Analysis of incorrect options:** * **Surface Antigen (HBsAg):** This is the outer lipoprotein envelope of the Dane particle. It is produced in excess, appearing as spherical and tubular forms in the serum. * **Core Antigen (HBcAg):** This forms the inner nucleocapsid that encloses the viral genome (partially double-stranded DNA) and the DNA polymerase. * **C-antigen (HBeAg):** This is a soluble protein derived from the precore/core gene. While it is primarily a secretory protein used as a marker of high infectivity, it is structurally associated with the core components of the virus. **Clinical Pearls for NEET-PG:** * **Morphology:** Dane particles are 42 nm; non-infectious spherical/tubular HBsAg particles are 22 nm. * **HBeAg:** Its presence indicates active viral replication and high infectivity. * **Window Period:** The time between the disappearance of HBsAg and the appearance of Anti-HBs; **Anti-HBc IgM** is the only diagnostic marker during this phase. * **Ground-glass Hepatocytes:** Characteristic histopathological finding in chronic HBV infection due to HBsAg accumulation.

Question 632: A 40-year-old patient presents with tumor-like lesions on the arms, legs, and buttocks. Histology showed hyaline acidophilic inclusion bodies. What is the diagnosis?

A. Cowpox
B. Milker's nodule
C. Orf
D. Molluscum contagiosum (Correct Answer)

Explanation: ### Explanation **Correct Answer: D. Molluscum contagiosum** The clinical presentation of tumor-like skin lesions combined with the specific histological finding of **hyaline acidophilic inclusion bodies** is pathognomonic for **Molluscum contagiosum**. These inclusions, known as **Henderson-Patterson bodies**, are large, eosinophilic, intracytoplasmic structures found in the stratum spinosum and stratum corneum. They represent the site of viral replication (Poxvirus) and displace the host cell nucleus to the periphery. Clinically, these lesions appear as pearly, umbilicated papules. **Why other options are incorrect:** * **Cowpox (A):** While it is a Poxvirus, it typically presents as a single painful, inflamed pustule or ulcer (usually on the hands) acquired from infected animals. It shows **Guarnieri bodies** (intracytoplasmic inclusions), but not the classic Henderson-Patterson bodies. * **Milker's nodule (B):** Caused by the Parapoxvirus, it presents as small, red-to-purple nodules on the fingers of those handling infected cattle. Histology shows vacuolization of the epidermis but lacks the large hyaline inclusions of Molluscum. * **Orf (C):** Also a Parapoxvirus (from sheep/goats), it presents as a solitary "targetoid" nodule that progresses through stages (maculopapular to necrotic). It does not produce the characteristic hyaline bodies seen in this case. **High-Yield Clinical Pearls for NEET-PG:** * **Henderson-Patterson bodies:** Large, eosinophilic, intracytoplasmic inclusions (Molluscum). * **Guarnieri bodies:** Intracytoplasmic inclusions seen in Smallpox and Vaccinia. * **Paschen bodies:** Smallest infectious particles of Variola virus. * **Clinical sign:** Look for "umbilicated papules" in the history. In adults, if lesions are extensive or involve the face, consider **HIV/Immunosuppression**.

Question 633: Which of the following is the most common oral manifestation of infectious mononucleosis?

A. Bluish red spots opposite maxillary molars
B. Pseudomembrane on gingiva
C. Pinpoint petechiae on the palate (Correct Answer)
D. Gingival hyperplasia

Explanation: **Explanation:** **Infectious Mononucleosis (IM)**, primarily caused by the **Epstein-Barr Virus (EBV)**, is a systemic viral infection characterized by the triad of fever, pharyngitis, and lymphadenopathy. **Why the correct answer is right:** The most characteristic and common oral manifestation of IM is the presence of **palatal petechiae**. These are pinpoint, non-blanching red spots typically located at the junction of the hard and soft palate. They occur in approximately 25–60% of cases and are a high-yield diagnostic sign for clinicians. **Analysis of incorrect options:** * **A. Bluish red spots opposite maxillary molars:** These are **Koplik spots**, which are pathognomonic for **Measles (Rubeola)**, not IM. * **B. Pseudomembrane on gingiva:** While IM can cause an exudative pharyngitis/tonsillitis (pseudomembrane on tonsils), a pseudomembrane localized to the gingiva is more characteristic of **Acute Necrotizing Ulcerative Gingivitis (ANUG)** or Diphtheria. * **D. Gingival hyperplasia:** This is typically associated with medications (Phenytoin, Cyclosporine, Nifedipine) or conditions like AML (M5 subtype), but not viral infections like EBV. **High-Yield Clinical Pearls for NEET-PG:** * **Diagnosis:** Heterophile antibody test (**Monospot test**) is the screening test of choice. * **Hematology:** Peripheral smear shows **Atypical Lymphocytes (Downey cells)**, which are actually activated T-cells (CD8+). * **Clinical Caution:** Administration of **Ampicillin or Amoxicillin** in a patient with IM often results in a characteristic maculopapular skin rash. * **Complication:** Splenic rupture is a rare but life-threatening complication; patients are advised to avoid contact sports.

Question 634: All of the following are blood-borne infections except?

A. Hepatitis B
B. Hepatitis C
C. Hepatitis G
D. Hepatitis E (Correct Answer)

Explanation: **Explanation:** The core concept tested here is the **mode of transmission** of viral hepatitis. Hepatitis viruses are broadly categorized into two groups based on their transmission routes: **Enteric** (fecal-oral) and **Parenteral** (blood-borne). **Why Hepatitis E is the correct answer:** Hepatitis E Virus (HEV) is primarily transmitted via the **fecal-oral route**, usually through contaminated drinking water. It is not considered a blood-borne infection. While rare instances of transfusion-associated HEV have been reported, its classic and primary epidemiological classification remains enteric. **Why the other options are incorrect:** * **Hepatitis B (HBV):** A classic blood-borne pathogen transmitted through infected blood, needles, sexual contact, and vertically (mother to child). * **Hepatitis C (HCV):** Primarily transmitted through percutaneous exposure to infectious blood (e.g., IV drug use, unscreened blood transfusions). * **Hepatitis G (HGV/GBV-C):** A flavivirus known to be transmitted via blood and blood products, often found as a co-infection with HCV. **High-Yield NEET-PG Pearls:** * **Mnemonic "Vowels are Bowels":** Hepatitis **A** and **E** are transmitted via the fecal-oral route (Enteric). * **Hepatitis E & Pregnancy:** HEV infection in pregnant women (especially in the 3rd trimester) carries a high mortality rate (up to 20%) due to fulminant hepatic failure. * **Hepatitis D:** It is a "defective" virus that requires the HBsAg (Hepatitis B) coat to replicate; thus, it is also blood-borne. * **Chronicity:** Hepatitis A and E generally do not cause chronic infection (except HEV in immunocompromised hosts), whereas B, C, and D frequently lead to chronic carrier states.

Question 635: Kaposi's sarcoma is associated with which of the following viruses?

A. Hepatitis C virus (HCV)
B. Human Papillomavirus (HPV)
C. Herpes Simplex virus (HSV)
D. Human Herpesvirus (HHV) (Correct Answer)

Explanation: **Explanation:** Kaposi’s Sarcoma (KS) is a multicentric vascular neoplasm caused by **Human Herpesvirus 8 (HHV-8)**, also known as Kaposi’s Sarcoma-associated Herpesvirus (KSHV). The virus infects endothelial cells, leading to the characteristic proliferation of spindle cells, neoangiogenesis, and inflammation. It is most commonly seen in patients with advanced HIV/AIDS (AIDS-defining illness) but also occurs in endemic (African), classic (Mediterranean), and iatrogenic (transplant-related) forms. **Analysis of Options:** * **Hepatitis C virus (HCV):** Primarily associated with Hepatocellular Carcinoma (HCC) and B-cell Non-Hodgkin Lymphoma (via Mixed Cryoglobulinemia). * **Human Papillomavirus (HPV):** High-risk strains (16, 18) are the primary cause of Cervical, Anal, and Oropharyngeal squamous cell carcinomas. * **Herpes Simplex virus (HSV):** HSV-1 and HSV-2 cause vesicular lesions (oral/genital) and encephalitis but are not oncogenic. **High-Yield Clinical Pearls for NEET-PG:** * **HHV-8 Association:** Besides KS, HHV-8 is also the causative agent for **Primary Effusion Lymphoma (PEL)** and a variant of **Multicentric Castleman Disease**. * **Histology:** Look for "spindle-shaped cells" and "slit-like vascular spaces" containing extravasated RBCs. * **Transmission:** Primarily through saliva and sexual contact. * **Treatment:** In HIV patients, Highly Active Antiretroviral Therapy (HAART) often leads to regression of lesions. Localized cases may use intralesional vinblastine or liquid nitrogen.

Question 636: Bornholm's disease is caused by which of the following viruses?

A. Herpes Simplex Virus (HSV)
B. Hepatitis B Virus (HBV)
C. Coxsackie B virus (Correct Answer)
D. Human Papillomavirus (HPV)

Explanation: **Explanation:** **Bornholm’s disease**, also known as **Epidemic Pleurodynia** or "The Devil’s Grip," is caused by the **Coxsackie B virus** (an Enterovirus belonging to the Picornaviridae family). 1. **Why Coxsackie B is correct:** This virus primarily affects the intercostal muscles and the pleura. The underlying medical concept involves viral-induced myositis of the chest and upper abdominal walls. Clinically, it presents as sudden, paroxysmal, stabbing chest pain (pleurodynia) exacerbated by breathing or movement, often accompanied by fever and malaise. 2. **Why other options are incorrect:** * **HSV (A):** Primarily causes vesicular lesions of the skin or mucous membranes (e.g., cold sores, genital herpes) and encephalitis. * **HBV (B):** A hepadnavirus that targets the liver, leading to acute or chronic hepatitis and potentially hepatocellular carcinoma. * **HPV (C):** Associated with cutaneous warts, laryngeal papillomas, and mucosal malignancies (e.g., cervical cancer). **High-Yield Clinical Pearls for NEET-PG:** * **Coxsackie B** is also the most common viral cause of **Myocarditis** and **Pericarditis**. * **Coxsackie A** is typically associated with **Herpangina** and **Hand-Foot-Mouth Disease (HFMD)**. * **Aseptic Meningitis:** Both Coxsackie A and B are leading causes of viral meningitis. * **Seasonality:** Enteroviral infections typically peak during the summer and autumn months.

Question 637: What is the best serological test to diagnose the prodromal phase of Hepatitis A infection?

A. Hepatitis A virus (HAV) RNA in blood
B. IgG antibodies against HAV
C. IgM antibodies against HAV (Correct Answer)
D. HAV in stool

Explanation: **Explanation:** The diagnosis of acute Hepatitis A virus (HAV) infection relies on identifying markers that appear during the symptomatic phase, which includes the prodrome (fever, malaise, anorexia) and the icteric phase. **1. Why IgM anti-HAV is correct:** IgM antibodies against HAV are the **gold standard** for diagnosing acute infection. They become detectable in the blood at the onset of symptoms (the prodromal phase), coinciding with the rise in ALT/AST levels. These antibodies remain positive for 3 to 6 months, making them the most reliable marker for identifying a current or very recent infection. **2. Why other options are incorrect:** * **HAV RNA in blood (Option A):** While detectable via PCR, viremia in Hepatitis A is very brief and typically occurs *before* the onset of symptoms. It is rarely used in clinical practice. * **IgG anti-HAV (Option B):** These antibodies appear later and persist for life. They indicate past infection or immunity (via vaccination) but cannot distinguish an acute prodromal phase from old immunity. * **HAV in stool (Option C):** Viral shedding in feces is maximal *before* the onset of symptoms and usually declines rapidly once jaundice or the prodrome begins. While it is the source of transmission, it is not the preferred diagnostic test for a patient presenting with symptoms. **High-Yield Clinical Pearls for NEET-PG:** * **Transmission:** Fecal-oral route (most common in children). * **Incubation Period:** 2–6 weeks. * **Chronicity:** HAV **never** causes chronic hepatitis or a carrier state (unlike HBV and HCV). * **Complication:** The most serious (though rare) complication is Fulminant Hepatic Failure. * **Vaccination:** Provides long-term protection via IgG production.

Question 638: Zoster recurrence occurs after infection with which virus?

A. Herpes Simplex Virus 1 (HSV-1)
B. Herpes Simplex Virus 2 (HSV-2)
C. Varicella-Zoster Virus (VZV) (Correct Answer)
D. Variola Virus (Smallpox)

Explanation: **Explanation:** The correct answer is **Varicella-Zoster Virus (VZV)**, also known as Human Herpesvirus 3 (HHV-3). **Why VZV is correct:** VZV is characterized by its ability to cause two distinct clinical entities. The **primary infection** manifests as **Varicella (Chickenpox)**, typically in children. Following the resolution of the primary infection, the virus remains **latent** in the **dorsal root ganglia** or cranial nerve ganglia. Years or decades later, when cell-mediated immunity declines (due to age, stress, or immunosuppression), the virus reactivates and travels down the sensory nerves to the skin. This **recurrence** is known as **Herpes Zoster (Shingles)**, presenting as a painful, unilateral vesicular rash in a dermatomal distribution. **Why other options are incorrect:** * **HSV-1 & HSV-2:** While these also establish latency (HSV-1 in the trigeminal ganglia; HSV-2 in the sacral ganglia), their recurrence manifests as Herpes Labialis (cold sores) or Genital Herpes, respectively—not Zoster. * **Variola Virus:** This is a Poxvirus that caused Smallpox. Unlike Herpesviruses, Poxviruses do not establish latency and do not recur once the infection is cleared. **High-Yield Clinical Pearls for NEET-PG:** * **Tzanck Smear:** Used for rapid diagnosis of VZV and HSV; look for **Multinucleated Giant Cells** with Cowdry Type A intranuclear inclusion bodies. * **Complication:** The most common complication of Zoster is **Post-Herpetic Neuralgia (PHN)**. * **Ramsay Hunt Syndrome:** Reactivation of VZV in the geniculate ganglion involving the facial nerve (CN VII). * **Vaccine:** Both live-attenuated (Zostavax) and recombinant (Shingrix) vaccines are available to prevent Zoster in older adults.

Question 639: What is the Von Magnus phenomenon?

A. High hemagglutinin titre, low infectivity (Correct Answer)
B. High hemagglutinin titre, high infectivity
C. Low hemagglutinin titre, low infectivity
D. Low hemagglutinin titre, high infectivity

Explanation: ### Explanation: Von Magnus Phenomenon The **Von Magnus phenomenon** is a classic virological concept observed primarily with the **Influenza virus**. It occurs when a virus is passaged at a **high multiplicity of infection (MOI)**—meaning a large number of viruses infect a single host cell simultaneously. **1. Why Option A is Correct:** When cells are overloaded with influenza viruses, the rapid replication process becomes "sloppy," leading to the production of **defective interfering (DI) particles**. These particles contain incomplete or truncated RNA segments. * **High Hemagglutinin (HA) Titre:** These defective particles still possess surface HA spikes, which allow them to agglutinate red blood cells. * **Low Infectivity:** Because their internal genetic material is incomplete, they cannot undergo a full replication cycle in new host cells. Thus, the HA titre remains high, but the actual infectious titre (measured in EID₅₀ or TCID₅₀) drops significantly. **2. Why Other Options are Incorrect:** * **Option B:** This describes a standard, efficient viral infection where both structural proteins (HA) and functional genomes are produced in balance. * **Options C & D:** These do not align with the phenomenon, as the hallmark of Von Magnus is the **dissociation** between the presence of viral surface proteins (HA) and the ability to cause productive infection. **3. NEET-PG High-Yield Pearls:** * **Virus Association:** Most commonly associated with **Influenza virus** (Orthomyxoviridae). * **Mechanism:** Production of **Defective Interfering (DI) particles** due to high-density serial passage. * **Clinical Significance:** DI particles can actually interfere with the replication of "normal" infectious viruses, potentially modulating the severity of a viral infection. * **Measurement:** It is identified by a **low Infectivity/Hemagglutinin (I/A) ratio**.

Question 640: Pasteurella multocida is transmitted by?

A. Animal bite (Correct Answer)
B. Insect bite
C. Droplet infection
D. Sexual contact

Explanation: **Explanation:** *Pasteurella multocida* is a small, Gram-negative coccobacillus that exists as a commensal in the oral cavity and respiratory tract of many animals, most notably **cats and dogs**. **1. Why "Animal bite" is correct:** The primary mode of transmission to humans is through **animal bites or scratches**, particularly from cats (which have a higher carriage rate and sharper teeth that inoculate the bacteria deeply). Following a bite, it typically causes a rapidly progressing cellulitis (within 24 hours), characterized by intense pain, swelling, and serosanguinous discharge. **2. Why the other options are incorrect:** * **Insect bite:** Diseases like Malaria (mosquito) or Plague (*Yersinia pestis* via fleas) are transmitted this way. *Pasteurella* is not vector-borne. * **Droplet infection:** While *Pasteurella* can rarely cause respiratory infections in patients with underlying lung disease via inhalation, it is not the standard mode of transmission. Droplet spread is characteristic of *N. meningitidis* or *M. tuberculosis*. * **Sexual contact:** This is the route for STIs like Syphilis or Gonorrhea; *Pasteurella* has no association with sexual transmission. **Clinical Pearls for NEET-PG:** * **Bipolar Staining:** On Leishman or Wayson stain, it shows a characteristic **"safety-pin" appearance** (similar to *Yersinia pestis*). * **Culture:** It grows well on Blood Agar and Chocolate Agar but **fails to grow on MacConkey agar** (a key differentiating feature from other Gram-negative rods). * **Biochemicals:** It is Oxidase positive, Catalase positive, and Indole positive. * **Drug of Choice:** **Penicillin** is the treatment of choice, which is unique for a Gram-negative organism.

Practice by Chapter

Virus Structure and Classification

Practice Questions

Viral Replication

Practice Questions

Pathogenesis of Viral Infections

Practice Questions

DNA Viruses: Herpesviruses

Practice Questions

DNA Viruses: Poxviruses and Adenoviruses

Practice Questions

Hepatitis Viruses

Practice Questions

RNA Viruses: Orthomyxoviruses

Practice Questions

RNA Viruses: Paramyxoviruses

Practice Questions

Enteroviruses and Rhinoviruses

Practice Questions

Arboviruses

Practice Questions

HIV and Retroviruses

Practice Questions

Oncogenic Viruses

Practice Questions

Want unlimited practice?

Get full access to all questions, explanations, and performance tracking.

Start For Free

Virology — MCQs

Virology — MCQs

On this page

Practice by Chapter

Want unlimited practice?