Virology — MCQs
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A virus produces neonatal infections and infections in immunocompromised patients such as AIDS patients. The most common clinical presentation involves floaters, visual field deficits, and painless loss of vision. It can also produce encephalitis and may cause calcifying lesions in the CNS. What is this virus most likely?
A woman became pregnant 1 month after receiving the MMR vaccine, despite being advised to avoid pregnancy. What advice should the doctor give the patient?
Which subtype of HIV is predominantly found in West Africans?
What are prions?
Which of the following statements is TRUE?
Early diagnosis of active hepatitis B infection is done by which marker?
Which virus affects lymphoid tissue?
Which of the following is associated with nasopharyngeal cancer?
Fatal familial insomnia is associated with which type of disease?
All of the following are included in Jones major criteria except?
Virology Indian Medical PG Practice Questions and MCQs
Question 581: A virus produces neonatal infections and infections in immunocompromised patients such as AIDS patients. The most common clinical presentation involves floaters, visual field deficits, and painless loss of vision. It can also produce encephalitis and may cause calcifying lesions in the CNS. What is this virus most likely?
- A. Cytomegalovirus (CMV) (Correct Answer)
- B. Epstein-Barr Virus (EBV)
- C. Herpes Simplex Virus (HSV)
- D. Human Immunodeficiency Virus (HIV)
Explanation: ### Explanation The clinical presentation described is classic for **Cytomegalovirus (CMV)**, a member of the Beta-herpesvirinae family. **Why CMV is the correct answer:** 1. **Ocular Involvement:** CMV retinitis is the most common opportunistic ocular infection in AIDS patients (typically when CD4 <50 cells/mm³). It presents with **painless vision loss**, floaters, and a characteristic "pizza-pie" appearance (hemorrhage and exudates) on fundoscopy. 2. **Congenital Infection:** CMV is the most common cause of congenital viral infection. Key features include **periventricular calcifications**, microcephaly, and sensorineural hearing loss. 3. **Immunocompromised State:** In addition to retinitis, it causes esophagitis (linear ulcers) and encephalitis in late-stage HIV. **Why other options are incorrect:** * **EBV:** Primarily associated with Infectious Mononucleosis, Oral Hairy Leukoplakia, and malignancies (Burkitt lymphoma, Nasopharyngeal carcinoma). It does not typically cause retinitis or CNS calcifications. * **HSV:** HSV-1 causes sporadic encephalitis (targeting the **temporal lobes**), but it does not cause periventricular calcifications. Neonatal HSV usually presents with skin-eye-mouth lesions or disseminated disease. * **HIV:** While HIV causes the underlying immunosuppression, the specific triad of retinitis, neonatal calcifications, and opportunistic CNS lesions points directly to the secondary pathogen, CMV. **High-Yield Clinical Pearls for NEET-PG:** * **Histology:** "Owl’s eye" intranuclear inclusion bodies. * **Congenital CMV:** Periventricular calcifications (vs. Toxoplasmosis, which shows diffuse/scattered calcifications). * **Drug of Choice:** Ganciclovir (Valganciclovir for prophylaxis). * **Culture:** Human fibroblast cell lines are used for isolation.
Question 582: A woman became pregnant 1 month after receiving the MMR vaccine, despite being advised to avoid pregnancy. What advice should the doctor give the patient?
- A. Wait and watch (Correct Answer)
- B. Termination of pregnancy is mandatory
- C. Low risk; termination of pregnancy may be considered
- D. High risk of anomalies; consider termination
Explanation: **Explanation:** The MMR vaccine is a **live-attenuated vaccine** containing Measles, Mumps, and Rubella strains. Historically, there has been a theoretical concern that the live Rubella virus in the vaccine could cross the placenta and cause **Congenital Rubella Syndrome (CRS)** if administered just before or during pregnancy. **Why "Wait and Watch" is correct:** Current clinical guidelines (CDC and WHO) recommend avoiding pregnancy for **28 days (1 month)** after MMR vaccination. However, extensive registry data of women who inadvertently received the vaccine shortly before or during pregnancy have shown **zero cases of CRS**. While the vaccine virus can infect the fetus, it has not been shown to be teratogenic. Therefore, accidental vaccination is **not** an indication for termination of pregnancy. The patient should be reassured and monitored with routine prenatal care. **Analysis of Incorrect Options:** * **B & D:** These are incorrect because the risk of fetal malformation from the vaccine strain is purely theoretical and has never been documented in clinical practice. Termination is never "mandatory" for MMR exposure. * **C:** While the risk is indeed "low" (effectively zero), suggesting termination "may be considered" creates unnecessary anxiety for a situation where no clinical evidence of harm exists. **NEET-PG High-Yield Pearls:** * **Interval:** The recommended gap between MMR vaccination and conception is **4 weeks (28 days)**. * **Contraindication:** Pregnancy is a general contraindication for all live vaccines (except in specific high-risk scenarios like Yellow Fever). * **Postpartum:** MMR is safe and recommended for non-immune women in the immediate postpartum period, even if breastfeeding. * **Household contacts:** It is safe to vaccinate children or household members of a pregnant woman with MMR; the virus is not transmitted from the vaccinee.
Question 583: Which subtype of HIV is predominantly found in West Africans?
- A. HIV 1
- B. HIV 2 (Correct Answer)
- C. HIV 3
- D. HIV 4
Explanation: **Explanation:** **HIV-2** is the correct answer because it is geographically restricted primarily to **West Africa** (e.g., Senegal, Guinea-Bissau, Gambia, and Ivory Coast). It originated from the Sooty Mangabey monkey and is characterized by lower transmissibility and a slower progression to AIDS compared to HIV-1. **Analysis of Options:** * **Option A (HIV-1):** This is the most common cause of the global AIDS pandemic. While it is found worldwide, including Africa, it is not the "predominant" subtype unique to the West African region. HIV-1 is further divided into groups M (Major), N, O, and P, with Group M being responsible for most infections globally. * **Options C & D (HIV-3 and HIV-4):** These are **not recognized classifications** of the Human Immunodeficiency Virus. The virus is strictly categorized into two main types: HIV-1 and HIV-2. **High-Yield Clinical Pearls for NEET-PG:** * **Diagnosis:** HIV-2 is often suspected when a patient from West Africa shows clinical signs of immunodeficiency but tests negative on standard HIV-1 specific PCR or shows an indeterminate Western Blot. * **Treatment Resistance:** HIV-2 is **intrinsically resistant to Non-Nucleoside Reverse Transcriptase Inhibitors (NNRTIs)** like Nevirapine and Efavirenz. It is also less sensitive to some Protease Inhibitors. * **Virulence:** HIV-2 has a lower viral load and a longer asymptomatic period than HIV-1. * **Screening:** Modern 4th generation ELISA kits detect antibodies to both HIV-1 and HIV-2, as well as the p24 antigen (though p24 is specific to HIV-1).
Question 584: What are prions?
- A. Particles composed of bacterial and viral components
- B. Immunogenic
- C. Infectious (Correct Answer)
- D. RNA particles
Explanation: **Explanation:** **Prions** (Proteinaceous Infectious Particles) are unique pathogens that consist entirely of proteins and lack any nucleic acid (DNA or RNA). 1. **Why "Infectious" is correct:** Prions are misfolded forms of a normal cellular protein ($PrP^C$). When the abnormal form ($PrP^{Sc}$) enters a healthy host, it acts as a template, inducing normal proteins to refold into the infectious, beta-sheet-rich conformation. This leads to neurodegeneration and is the hallmark of transmissibility in diseases like Creutzfeldt-Jakob Disease (CJD). 2. **Why other options are incorrect:** * **Option A:** Prions are purely proteinaceous; they contain no bacterial or viral structural components. * **Option B:** Prions are **non-immunogenic**. Because they are misfolded versions of the body's own proteins, the immune system does not recognize them as foreign, meaning there is no inflammatory response or antibody production. * **Option D:** Prions are devoid of nucleic acids. Particles consisting solely of RNA are called **Viroids** (which primarily infect plants). **High-Yield Clinical Pearls for NEET-PG:** * **Resistance:** Prions are highly resistant to standard sterilization methods, including boiling, UV radiation, and formalin. They are inactivated by **autoclaving at 134°C for 1 hour** or using **1N NaOH**. * **Histopathology:** Characterized by **spongiform degeneration** (vacuolation of neurons), neuronal loss, and amyloid plaques without inflammation. * **Key Diseases:** Kuru (associated with cannibalism), Creutzfeldt-Jakob Disease (CJD), Bovine Spongiform Encephalopathy (Mad Cow Disease), and Fatal Familial Insomnia.
Question 585: Which of the following statements is TRUE?
- A. Hantavirus pulmonary syndrome is caused by inhalation of rodent feces. (Correct Answer)
- B. Kyasanur Forest Disease (KFD) is caused by the bite of a wild animal.
- C. Lyssavirus is transmitted by ticks.
- D. Yellow fever is transmitted by Anopheles mosquito.
Explanation: ### Explanation **Correct Option: A** **Hantavirus Pulmonary Syndrome (HPS)** is caused by viruses of the family *Bunyaviridae*. The primary mode of transmission is **aerosolization**. Rodents (like the deer mouse) serve as the reservoir; the virus is shed in their urine, saliva, and feces. When these dried materials are disturbed, humans inhale the contaminated dust, leading to severe respiratory failure. **Analysis of Incorrect Options:** * **B. Kyasanur Forest Disease (KFD):** While it is associated with monkeys (hence "Monkey Fever"), the actual transmission to humans occurs via the bite of an infected **Hard Tick (*Haemaphysalis spinigera*)**, not the bite of the animal itself. * **C. Lyssavirus:** This genus includes the **Rabies virus**. It is transmitted through the bite or scratch of an infected mammal (dogs, bats), where the virus is present in the **saliva**. It is not tick-borne. * **D. Yellow Fever:** This is a viral hemorrhagic fever transmitted primarily by the **Aedes aegypti** mosquito (and *Haemagogus* in jungles). *Anopheles* mosquitoes are the vectors for Malaria, not Yellow Fever. **NEET-PG High-Yield Pearls:** * **Hantavirus Unique Feature:** Unlike most Bunyaviruses, Hantavirus is **NOT** arthropod-borne (it is a non-arbovirus). * **KFD:** Endemic to Karnataka, India; characterized by biphasic fever and hemorrhagic manifestations. * **Yellow Fever:** Look for "Councilman bodies" (acidophilic degeneration of hepatocytes) on liver biopsy. * **Vector Quick-Check:** * *Aedes:* Dengue, Chikungunya, Zika, Yellow Fever. * *Culex:* Japanese Encephalitis, West Nile Virus, Filariasis. * *Ticks:* KFD, CCHF, Rickettsial diseases.
Question 586: Early diagnosis of active hepatitis B infection is done by which marker?
- A. IgM anti-HBc (Correct Answer)
- B. HBsAg
- C. HBcAg
- D. IgE anti-HBs
Explanation: **Explanation:** The diagnosis of acute Hepatitis B virus (HBV) infection relies on the detection of specific serological markers. **Why IgM anti-HBc is the correct answer:** While HBsAg is the first marker to appear in the blood, **IgM anti-HBc** is the definitive marker for **active/acute infection**. Its clinical significance is paramount during the **"Window Period"**—the interval when HBsAg has disappeared but anti-HBs antibodies have not yet reached detectable levels. During this gap, IgM anti-HBc is the *only* serological marker present that indicates an active, acute infection. **Analysis of Incorrect Options:** * **HBsAg (Option B):** This is the first marker to appear (as early as 2–6 weeks post-exposure) and indicates the presence of the virus. However, it only signifies that the person is "infected" (either acute or chronic); it does not specifically differentiate a new, active infection from a chronic state as reliably as IgM anti-HBc. * **HBcAg (Option C):** This is a particulate antigen found within the hepatocyte nuclei. It is **not** detectable in the serum and therefore cannot be used as a diagnostic blood marker. * **IgE anti-HBs (Option D):** This is a distractor. The relevant antibody is **IgG anti-HBs**, which indicates immunity (via vaccination or recovery), not active infection. **High-Yield Clinical Pearls for NEET-PG:** * **Window Period Marker:** IgM anti-HBc. * **First marker to appear:** HBsAg. * **Indicator of high infectivity/replication:** HBeAg. * **Marker of immunity/recovery:** Anti-HBs. * **Chronic Infection:** Defined by the persistence of HBsAg for >6 months.
Question 587: Which virus affects lymphoid tissue?
- A. Adenovirus
- B. Herpes virus (Correct Answer)
- C. Cytomegalovirus (CMV)
- D. Human Immunodeficiency Virus (HIV)
Explanation: **Explanation:** The **Herpesviridae** family is characterized by its ability to establish lifelong latent infections. A defining feature of several members of this family is their specific tropism for **lymphoid tissue**. Specifically, the **Gammaherpesvirinae** subfamily (which includes **Epstein-Barr Virus (EBV)** and **Human Herpesvirus 8 (HHV-8)**) targets lymphocytes for replication and latency. EBV, the causative agent of Infectious Mononucleosis, infects B-lymphocytes via the CD21 receptor, leading to lymphoid hyperplasia and the characteristic "atypical lymphocytes" (Downey cells) seen on peripheral smears. **Analysis of Options:** * **Option B (Herpes virus):** Correct. As a family, Herpesviruses are the classic example of viruses that utilize lymphoid tissue for latency (EBV in B-cells, CMV in mononuclear cells, HHV-6/7 in T-cells). * **Option A (Adenovirus):** While Adenoviruses can persist in tonsillar lymphoid tissue, their primary pathogenesis involves respiratory, ocular, and gastrointestinal epithelial cells. * **Option C (CMV):** Although CMV is a Herpesvirus (HHV-5), the question asks for the broader category. CMV primarily targets monocytes, neutrophils, and vascular endothelial cells rather than being the "prototypical" lymphoid virus compared to the family as a whole. * **Option D (HIV):** While HIV infects CD4+ T-cells, it is classified as a Retrovirus. In the context of standard microbiology examinations, the Herpes family is the classic answer for viruses with a primary affinity for establishing latency within the lymphoid system. **High-Yield Clinical Pearls for NEET-PG:** * **EBV Receptor:** CD21 (also the receptor for C3d complement). * **Latency Sites:** * HSV-1/HSV-2: Sensory Ganglia. * VZV: Dorsal Root Ganglia. * EBV: B-lymphocytes. * CMV: Monocytes/Bone marrow stem cells. * **Paul Bunnell Test:** Used to detect heterophile antibodies in EBV-induced Infectious Mononucleosis.
Question 588: Which of the following is associated with nasopharyngeal cancer?
- A. Human Herpesvirus 4 (HHV-4) (Correct Answer)
- B. Human Herpesvirus 1 (HHV-1)
- C. Human Herpesvirus 2 (HHV-2)
- D. Human Herpesvirus 3 (HHV-3)
Explanation: **Explanation:** The correct answer is **Human Herpesvirus 4 (HHV-4)**, commonly known as the **Epstein-Barr Virus (EBV)**. EBV is a potent oncogenic virus that infects B-lymphocytes and epithelial cells. Its association with **Nasopharyngeal Carcinoma (NPC)** is well-established, particularly the undifferentiated type (WHO Type III). The virus enters epithelial cells via the CD21 receptor (or through fusion) and establishes latency. Viral proteins, specifically **LMP-1 (Latent Membrane Protein 1)**, act as oncogenes by mimicking CD40 signaling, leading to cell proliferation and inhibition of apoptosis. **Analysis of Incorrect Options:** * **HHV-1 (Herpes Simplex Virus-1):** Primarily associated with orofacial lesions (herpes labialis), gingivostomatitis, and sporadic viral encephalitis. It is not oncogenic. * **HHV-2 (Herpes Simplex Virus-2):** Primarily causes genital herpes and neonatal herpes. While once studied for a link to cervical cancer, Human Papillomavirus (HPV) is the actual causative agent. * **HHV-3 (Varicella-Zoster Virus):** Causes chickenpox (primary infection) and shingles (reactivation). It does not have any known association with malignancy. **High-Yield Clinical Pearls for NEET-PG:** * **EBV-Associated Malignancies:** Apart from NPC, EBV is linked to **Burkitt Lymphoma** (starry-sky appearance, t(8;14)), Hodgkin Lymphoma (Mixed cellularity type), and Primary CNS Lymphoma in AIDS patients. * **Diagnostic Marker:** Elevated titers of **IgA antibodies against EBV Viral Capsid Antigen (VCA)** are used for screening and monitoring recurrence in NPC patients. * **Other Oncogenic Viruses:** Remember HHV-8 is associated with **Kaposi Sarcoma**, and HPV 16/18 are linked to cervical and oropharyngeal cancers.
Question 589: Fatal familial insomnia is associated with which type of disease?
- A. Prion disease (Correct Answer)
- B. Degeneration disease
- C. Neoplastic disease
- D. Vascular disease
Explanation: **Explanation:** **Fatal Familial Insomnia (FFI)** is a rare, autosomal dominant inherited disorder caused by a mutation in the **PRNP gene** (specifically at codon 178). This mutation leads to the misfolding of the normal cellular prion protein ($PrP^C$) into an abnormal, protease-resistant isoform ($PrP^{Sc}$). These prions accumulate primarily in the **thalamus**, leading to neuronal loss and gliosis. * **Why Option A is correct:** FFI belongs to the group of **Transmissible Spongiform Encephalopathies (TSEs)** or Prion diseases. It is characterized clinically by progressive insomnia, autonomic dysfunction (tachycardia, hyperhidrosis), and motor signs, eventually leading to death. * **Why Options B, C, and D are incorrect:** While FFI involves neurodegeneration, it is specifically classified by its unique **proteinaceous infectious** etiology (Prions). It is not caused by uncontrolled cell growth (Neoplastic), ischemia/hemorrhage (Vascular), or standard age-related wear-and-tear (Degeneration) in the absence of prion proteins. **High-Yield Clinical Pearls for NEET-PG:** * **Prion Characteristics:** They are devoid of nucleic acids and resistant to standard sterilization (autoclaving at 121°C). They require **134°C for 1 hour** or 1N NaOH for disinfection. * **The "178/129" Rule:** FFI occurs when there is a mutation at **Codon 178** combined with **Methionine** at Codon 129. If Valine is present at Codon 129 with the same 178 mutation, it results in **Creutzfeldt-Jakob Disease (CJD)**. * **Other Prion Diseases:** Kuru (associated with cannibalism), Gerstmann-Sträussler-Scheinker (GSS) syndrome, and Bovine Spongiform Encephalopathy (Mad Cow Disease).
Question 590: All of the following are included in Jones major criteria except?
- A. Lymphadenopathy (Correct Answer)
- B. Polyarthritis
- C. Sydenham's chorea
- D. Pancarditis
Explanation: The **Jones Criteria** are used for the clinical diagnosis of **Acute Rheumatic Fever (ARF)**, a non-suppurative sequela of Group A Streptococcal (GAS) pharyngitis. ### **Explanation of the Correct Answer** **A. Lymphadenopathy:** This is the correct answer because it is **not** part of the Jones Criteria. While lymphadenopathy may occur during the initial streptococcal throat infection, it is not a diagnostic feature of the subsequent autoimmune inflammatory process that defines Rheumatic Fever. ### **Analysis of Incorrect Options (Major Criteria)** The mnemonic **"J♥NES"** helps recall the Major Criteria: * **B. Polyarthritis (J - Joints):** Migratory polyarthritis involving large joints is the most common major manifestation. * **D. Pancarditis (♥ - Carditis):** Inflammation affecting the endocardium, myocardium, and pericardium. It is the only manifestation that can lead to chronic valvular heart disease. * **C. Sydenham's chorea (N - Nodes/Neurological):** Characterized by rapid, purposeless movements; it is a late manifestation. * **Erythema Marginatum (E):** A pink, evanescent, non-pruritic macular rash with serpiginous borders. * **Subcutaneous Nodules (S):** Small, painless, firm lumps typically found over bony prominences. ### **High-Yield Clinical Pearls for NEET-PG** 1. **Diagnosis Requirement:** For a primary episode, diagnosis requires **2 Major** OR **1 Major + 2 Minor** criteria, plus evidence of a preceding GAS infection (e.g., elevated ASO titer). 2. **Minor Criteria:** Include fever, arthralgia, prolonged PR interval on ECG, and elevated acute phase reactants (ESR/CRP). 3. **Most Common Valve Involved:** Mitral valve (Mitral Regurgitation in acute phase; Mitral Stenosis in chronic phase). 4. **Aschoff Bodies:** Pathognomonic histological finding in the myocardium consisting of Anitschkow cells ("caterpillar cells").
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Virus Structure and Classification
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Viral Replication
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Pathogenesis of Viral Infections
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DNA Viruses: Herpesviruses
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DNA Viruses: Poxviruses and Adenoviruses
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Hepatitis Viruses
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RNA Viruses: Orthomyxoviruses
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RNA Viruses: Paramyxoviruses
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Enteroviruses and Rhinoviruses
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Arboviruses
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HIV and Retroviruses
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Oncogenic Viruses
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