Virology — MCQs

Virology Indian Medical PG Practice Questions and MCQs

Question 491: What is true about HSV encephalitis?

A. Caused by HSV-1
B. Hemorrhagic lesion seen
C. Eosinophilic inclusion bodies seen
D. All of the above (Correct Answer)

Explanation: **Explanation:** Herpes Simplex Virus (HSV) encephalitis is the most common cause of sporadic fatal encephalitis worldwide. The correct answer is **D (All of the above)** based on the following clinical and pathological features: 1. **Causative Agent (Option A):** In adults and children beyond the neonatal period, HSV encephalitis is almost exclusively caused by **HSV-1** (usually due to reactivation of the virus in the trigeminal ganglion). In contrast, HSV-2 is more commonly associated with neonatal encephalitis and aseptic meningitis. 2. **Pathology (Option B):** A hallmark of HSV encephalitis is its predilection for the **temporal lobes**. It causes necrotizing, **hemorrhagic inflammation**, which can be visualized as hyperintensities on MRI (T2/FLAIR) and often leads to focal neurological deficits or seizures. 3. **Histology (Option C):** Microscopic examination of infected brain tissue reveals characteristic **Cowdry Type A inclusion bodies**. These are intranuclear, **eosinophilic** (acidophilic) droplets surrounded by a clear halo, representing viral replication sites. **High-Yield Clinical Pearls for NEET-PG:** * **Site Predilection:** Temporal lobes and orbital-frontal cortex (look for "temporal lobe involvement" in clinical vignettes). * **Diagnosis:** **CSF PCR** is the gold standard (highly sensitive and specific). * **EEG Findings:** Periodic lateralized epileptiform discharges (PLEDs). * **Treatment:** Immediate IV **Acyclovir** is the drug of choice; do not wait for PCR results if clinical suspicion is high. * **Clinical Sign:** Patients may present with sudden onset fever, headache, and psychiatric symptoms/personality changes (due to temporal lobe necrosis).

Question 492: What oncogenic risk is associated with HPV types 6 and 11?

A. High
B. Low (Correct Answer)
C. None
D. Variable

Explanation: **Explanation:** Human Papillomavirus (HPV) is a double-stranded DNA virus with over 100 genotypes, classified based on their association with malignancy. **Why Option B is Correct:** HPV types **6 and 11** are classified as **low-risk types**. While they are highly infectious and cause significant morbidity, they rarely integrate their DNA into the host genome. Instead, they typically exist as episomes (extrachromosomal DNA), leading to benign epithelial proliferations rather than invasive squamous cell carcinoma. They are the primary causative agents of **Condyloma acuminata** (anogenital warts) and **Laryngeal Papillomatosis**. **Why Other Options are Incorrect:** * **Option A (High):** High-risk types include **HPV 16 and 18** (most common), along with 31 and 33. These types produce E6 and E7 oncoproteins that inhibit p53 and Rb tumor suppressor proteins, respectively, leading to cervical, anal, and oropharyngeal cancers. * **Option C (None):** While "low risk," these types are not "no risk." Rare cases of malignant transformation (e.g., Buschke-Löwenstein tumors) can occur, particularly in immunocompromised states. * **Option D (Variable):** HPV risk is consistently categorized by genotype; 6 and 11 are strictly defined in the low-risk category in clinical oncology. **High-Yield NEET-PG Pearls:** * **Laryngeal Papillomatosis:** HPV 6 and 11 are the most common cause of benign tumors of the larynx in children (acquired during birth). * **Vaccination:** The Quadrivalent (Gardasil) and Nonavalent vaccines cover types 6 and 11 to prevent genital warts. * **Koilocytes:** The hallmark cytological finding of HPV infection (shrunken "raisin-like" nucleus with a large perinuclear halo).

Question 493: In an epidemic of hepatitis E, infection in which of the following groups carries a poor prognosis?

A. Malnourished male
B. Pregnant women (Correct Answer)
C. Anaemic male
D. Postmenopausal women

Explanation: **Explanation:** Hepatitis E Virus (HEV), a single-stranded RNA virus transmitted via the feco-oral route, is generally a self-limiting disease with a low case fatality rate (0.5–3%). However, it is notorious for its **high mortality rate (up to 20–25%) in pregnant women**, particularly during the **third trimester**. **Why Pregnant Women?** The poor prognosis in pregnancy is attributed to a combination of factors: * **Hormonal Changes:** High levels of estrogen and progesterone suppress cell-mediated immunity. * **Cytokine Shift:** A shift from Th1 to Th2 immune response makes the mother more susceptible to viral replication. * **Complications:** HEV in pregnancy frequently leads to **Fulminant Hepatic Failure (FHF)**, Disseminated Intravascular Coagulation (DIC), and obstetric complications like premature delivery or postpartum hemorrhage. **Analysis of Incorrect Options:** * **A & C (Malnourished/Anaemic Males):** While malnutrition and anemia can impair general immunity, they do not specifically predispose an individual to the fulminant hepatic failure characteristic of HEV infection. * **D (Postmenopausal Women):** The specific immunological and hormonal milieu of pregnancy is absent in postmenopausal women; their risk profile remains similar to the general population. **High-Yield Clinical Pearls for NEET-PG:** * **Virus Family:** Hepeviridae (Non-enveloped RNA virus). * **Transmission:** Feco-oral (Water-borne epidemics). * **Zoonotic Potential:** HEV Genotype 3 and 4 are associated with consumption of undercooked pork. * **Chronic Infection:** HEV can cause chronic hepatitis in **organ transplant recipients** and immunocompromised patients. * **Diagnosis:** IgM anti-HEV is the gold standard for acute infection.

Question 494: Which chemokine co-receptor for HIV is found on macrophages?

A. CD4
B. CD8
C. CCR5 (Correct Answer)
D. CXCR4

Explanation: ### Explanation HIV entry into host cells is a multi-step process requiring both a primary receptor and a co-receptor. The primary receptor for HIV is the **CD4 molecule**, while the co-receptors are members of the chemokine receptor family. **1. Why CCR5 is correct:** HIV-1 strains are classified based on their co-receptor tropism. **M-tropic (Macrophage-tropic)** strains, also known as R5 strains, utilize the **CCR5** co-receptor. These strains are typically responsible for the initial infection and are found on macrophages, dendritic cells, and memory T-cells. **2. Analysis of Incorrect Options:** * **CD4 (Option A):** This is the **primary receptor** for HIV, not a chemokine co-receptor. It is found on T-helper cells, macrophages, and monocytes. * **CD8 (Option B):** This is a marker for cytotoxic T-cells. HIV does not typically infect CD8+ cells as they lack the CD4 receptor. * **CXCR4 (Option D):** This is the co-receptor for **T-tropic (T-cell-tropic)** or X4 strains. These strains emerge later in the course of the disease and are associated with a rapid decline in CD4 counts and progression to AIDS. **3. High-Yield Clinical Pearls for NEET-PG:** * **Maraviroc:** A CCR5 antagonist (entry inhibitor) used in HIV treatment; it is only effective against R5-tropic strains. * **CCR5-Δ32 Mutation:** A 32-base pair deletion in the CCR5 gene. Individuals homozygous for this mutation are resistant to HIV infection, while heterozygotes show delayed progression to AIDS. * **gp120 & gp41:** The viral envelope protein **gp120** binds to CD4 and the co-receptor, while **gp41** mediates the fusion of the viral envelope with the host cell membrane.

Question 495: Which of the following is NOT a viral inclusion body?

A. Psammoma bodies (Correct Answer)
B. Molluscum bodies
C. Negri bodies
D. Bollinger bodies

Explanation: **Explanation:** Inclusion bodies are characteristic aggregates (usually proteins) found in the cytoplasm or nucleus of cells infected by specific viruses. They serve as "viral factories" or sites of viral assembly. **Why Psammoma bodies is the correct answer:** Psammoma bodies are **not** viral inclusions. They are microscopic, concentric lamellated calcifications. They are associated with specific **neoplastic conditions** (e.g., Papillary thyroid carcinoma, Serous papillary ovarian cystadenocarcinoma, and Meningioma) rather than viral infections. **Analysis of incorrect options (Viral Inclusions):** * **Molluscum bodies (Henderson-Patterson bodies):** Large, eosinophilic cytoplasmic inclusions seen in keratinocytes infected by the *Molluscum contagiosum* virus (Poxvirus). * **Negri bodies:** Pathognomonic intracytoplasmic, eosinophilic inclusions found in the pyramidal cells of the hippocampus and Purkinje cells of the cerebellum in **Rabies**. * **Bollinger bodies:** Large granular eosinophilic cytoplasmic inclusions seen in **Fowlpox**. (Note: Borrel bodies are the smaller minute particles found within Bollinger bodies). **High-Yield Clinical Pearls for NEET-PG:** * **Intranuclear Inclusions:** * *Cowdry Type A:* Herpes Simplex Virus (HSV), Varicella-Zoster Virus (VZV). * *Cowdry Type B:* Poliovirus. * *Owl’s Eye appearance:* Cytomegalovirus (CMV) — Note: CMV shows both intranuclear and intracytoplasmic inclusions. * **Intracytoplasmic Inclusions:** * *Guarnieri bodies:* Smallpox (Variola). * *Torres bodies:* Yellow Fever. * **Mnemonic for Psammoma bodies (PSaMM):** **P**apillary (thyroid), **S**erous (ovary), **M**eningioma, **M**esothelioma.

Question 496: Which of the following viruses causes an acute febrile rash and produces disease in immunocompetent children but has been associated with transient aplastic crises in persons with sickle cell disease?

A. Rubella
B. Varicella-zoster virus
C. Parvovirus B19 (Correct Answer)
D. Measles

Explanation: **Explanation:** **Parvovirus B19** is the correct answer because it is the causative agent of **Erythema Infectiosum (Fifth Disease)**. In immunocompetent children, it typically presents as an acute febrile illness followed by a characteristic "slapped-cheek" rash. The underlying medical concept involves the virus's tropism for **erythroid progenitor cells**. Parvovirus B19 binds to the **P-antigen** (globoside) on red blood cell precursors and replicates within them, leading to temporary cessation of erythropoiesis. In healthy individuals, this is clinically insignificant. However, in patients with high red cell turnover (e.g., **Sickle Cell Disease**, Hereditary Spherocytosis, or Thalassemia), this pause results in a life-threatening **Transient Aplastic Crisis (TAC)**, characterized by a sudden drop in hemoglobin and a low reticulocyte count. **Why other options are incorrect:** * **Rubella:** Causes "German Measles" with post-auricular lymphadenopathy and a maculopapular rash, but does not affect erythropoiesis or cause aplastic crises. * **Varicella-zoster virus:** Causes chickenpox (vesicular rash) and shingles. It is not associated with aplastic crises in sickle cell patients. * **Measles:** Presents with high fever, Cough, Coryza, Conjunctivitis (3 C's), and Koplik spots. While severe, it does not target erythroid precursors. **High-Yield NEET-PG Pearls:** * **Receptor:** P-antigen (Globoside). * **Fetal Infection:** Can cause **Hydrops Fetalis** due to severe fetal anemia (most common in the second trimester). * **Adults:** Often presents as symmetric polyarthritis (mimicking Rheumatoid Arthritis). * **Diagnosis:** Low reticulocyte count is the hallmark of Parvovirus-induced aplastic crisis.

Question 497: Varicella-Zoster virus is not associated with which of the following?

A. Latent infection
B. Chicken pox
C. Centrifugal rash (Correct Answer)
D. Thrombocytopenia

Explanation: **Explanation:** The correct answer is **Centrifugal rash** because Varicella-Zoster Virus (VZV) typically presents with a **centripetal rash**. In medical terminology, a centripetal distribution means the rash is most dense on the trunk (center) and less dense on the extremities (periphery). This is a classic hallmark of Chickenpox. **Analysis of Options:** * **Centrifugal rash (Correct Option):** This is characteristic of **Smallpox**, where the rash is more dense on the face and limbs than on the trunk. Since VZV causes a centripetal rash, this statement is incorrect regarding VZV. * **Latent infection:** VZV follows the pattern of all Herpesviruses by establishing lifelong latency. It remains dormant in the **dorsal root ganglia** or cranial nerve ganglia after the primary infection. * **Chickenpox:** This is the primary clinical manifestation of VZV infection in non-immune individuals (typically children). * **Thrombocytopenia:** While less common, VZV can cause hematological complications, including transient thrombocytopenia and idiopathic thrombocytopenic purpura (ITP), leading to "hemorrhagic chickenpox" in severe cases. **High-Yield Clinical Pearls for NEET-PG:** * **Pleomorphism:** VZV rash is "pleomorphic," meaning lesions at all stages (papules, vesicles, pustules, and crusts) are seen simultaneously in the same area ("starry sky" appearance). * **Dew-drop on a rose petal:** Classic description of the clear VZV vesicle on an erythematous base. * **Reactivation:** Reactivation of latent VZV results in **Herpes Zoster (Shingles)**, characterized by a painful, unilateral vesicular eruption along a specific dermatome. * **Diagnosis:** Tzanck smear shows **multinucleated giant cells** with Cowdry Type A intranuclear inclusion bodies.

Question 498: Paramyxoviruses enter the body via which route?

A. Blood
B. Respiratory route (Correct Answer)
C. Conjunctiva
D. Fecal-oral route

Explanation: ### Explanation **Correct Option: B. Respiratory route** Paramyxoviruses (which include Measles, Mumps, Parainfluenza, and Respiratory Syncytial Virus) are primarily transmitted through **respiratory droplets** or direct contact with infected secretions. Once inhaled, these viruses attach to the respiratory epithelium. For viruses like RSV and Parainfluenza, the infection remains localized to the respiratory tract. For others, like Measles and Mumps, the respiratory tract serves as the portal of entry before the virus undergoes primary viremia to spread to distant organs. **Analysis of Incorrect Options:** * **A. Blood:** While some paramyxoviruses (Measles/Mumps) cause viremia, the *initial entry* into the body is not via blood (unlike Hepatitis B or HIV). * **C. Conjunctiva:** Though the conjunctiva can be a secondary site of infection (e.g., Koplik spots or conjunctivitis in Measles), it is not the primary route of entry for this family. * **D. Fecal-oral route:** This is the characteristic route for Picornaviruses (like Polio or Hepatitis A) and Reoviruses (Rotavirus), but not Paramyxoviruses, which are enveloped and easily inactivated by gastric acid. **High-Yield Clinical Pearls for NEET-PG:** * **Structure:** Paramyxoviruses are pleomorphic, enveloped, **negative-sense ssRNA** viruses. * **Fusion (F) Protein:** All members possess an F-protein that mediates cell-to-cell fusion, leading to the formation of **multinucleated giant cells (syncytia)**—a classic histopathological finding (e.g., Warthin-Finkeldey cells in Measles). * **RSV:** The most common cause of bronchiolitis and pneumonia in infants. * **Vitamin A:** Supplementation reduces mortality in Measles by protecting the integrity of the respiratory epithelium.

Question 499: What is H5N1 commonly known as?

A. Bird flu virus (Correct Answer)
B. Vaccine for HIV
C. Causative agent of Japanese encephalitis
D. An eradicated virus

Explanation: **Explanation:** **H5N1** is a highly pathogenic strain of the **Influenza A virus**. The nomenclature "H5N1" refers to the specific subtypes of surface glycoproteins: **Hemagglutinin (H5)**, which facilitates viral entry into host cells, and **Neuraminidase (N1)**, which assists in the release of new viral particles. It is primarily an avian pathogen, hence the name **Bird Flu**. While it mainly affects poultry, it can cross the species barrier to humans through direct contact with infected birds, often resulting in severe respiratory illness with a high mortality rate (approx. 50-60%). **Analysis of Incorrect Options:** * **Option B:** There is currently no approved **vaccine for HIV** due to the virus's high mutation rate and integration into the host genome. * **Option C:** The causative agent of **Japanese encephalitis** is the Japanese Encephalitis Virus (JEV), a member of the *Flaviviridae* family, transmitted by *Culex* mosquitoes. * **Option D:** The only human virus officially declared **eradicated** by the WHO is Smallpox (*Variola virus*). H5N1 remains an active global health threat with pandemic potential. **High-Yield Clinical Pearls for NEET-PG:** * **Antigenic Shift:** Major genetic changes (reassortment) leading to pandemics (e.g., H1N1 in 2009). * **Antigenic Drift:** Minor point mutations causing seasonal epidemics; necessitates annual vaccine updates. * **Drug of Choice:** Neuraminidase inhibitors like **Oseltamivir** (Tamiflu) are used for treatment. * **Diagnosis:** Real-time RT-PCR is the gold standard for detecting Influenza A subtypes.

Question 500: What are the most common causes of acute and epidemic viral hepatitis?

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

Explanation: **Explanation:** The correct answer is **Hepatitis E and Hepatitis E** because Hepatitis E Virus (HEV) is recognized as the leading cause of both sporadic acute viral hepatitis and large-scale waterborne epidemics in developing countries, including India. 1. **Why Option B is Correct:** While Hepatitis A (HAV) and HEV both cause acute infection via the fecal-oral route, epidemiological data consistently shows that **HEV is the most common cause of acute sporadic hepatitis in adults** and the primary driver of **epidemic outbreaks** due to contaminated water supplies. In the Indian context, HEV accounts for over 50-70% of all cases of sporadic acute viral hepatitis. 2. **Why Other Options are Incorrect:** * **Option A (HAV):** HAV is a common cause of acute hepatitis, especially in children (who are often asymptomatic). However, it is less frequently the cause of large-scale adult epidemics compared to HEV. * **Option C (HBV & HCV):** These are primarily transmitted parenterally and are the leading causes of **chronic** hepatitis, cirrhosis, and hepatocellular carcinoma, rather than acute/epidemic outbreaks. * **Option D (HDV & HGV):** HDV requires HBV for replication (co-infection/superinfection) and is not a primary cause of epidemics. HGV (GB virus C) is generally non-pathogenic in humans. **High-Yield NEET-PG Pearls:** * **Pregnancy Risk:** HEV is notorious for high mortality (up to 20%) in pregnant women, particularly during the third trimester, due to fulminant hepatic failure. * **Transmission:** Fecal-oral route (Waterborne). * **Virology:** HEV is a non-enveloped, single-stranded RNA virus (Hepeviridae family). * **Zoonosis:** HEV Genotypes 3 and 4 are zoonotic, often linked to undercooked pork.

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