Virology — MCQs

Virology Indian Medical PG Practice Questions and MCQs

Question 171: What is the oropharyngeal manifestation of HIV infection?

A. Oral hairy leukoplakia (Correct Answer)
B. Caries tooth
C. Cheilitis
D. Pharyngitis

Explanation: **Explanation:** **Oral Hairy Leukoplakia (OHL)** is a classic opportunistic manifestation of HIV infection. It is caused by the reactivation of the **Epstein-Barr Virus (EBV)** in the setting of profound immunosuppression (typically when CD4 counts fall below 200-300 cells/mm³). Clinically, it presents as white, corrugated (ribbed), non-scrapable patches, most commonly found on the **lateral borders of the tongue**. Unlike oral candidiasis, these lesions cannot be rubbed off. **Analysis of Incorrect Options:** * **B. Caries tooth:** While poor oral hygiene can occur in any patient, dental caries is not a specific or diagnostic opportunistic manifestation of HIV/AIDS. * **C. Cheilitis:** Angular cheilitis (inflammation of the corners of the mouth) can be seen in HIV due to secondary *Candida* infections or nutritional deficiencies, but it is non-specific and occurs in many other conditions (e.g., iron deficiency). * **D. Pharyngitis:** While acute HIV syndrome (seroconversion) can present with a sore throat, chronic oropharyngeal pharyngitis is not a defining opportunistic feature of HIV in the same way OHL is. **High-Yield Clinical Pearls for NEET-PG:** * **Diagnostic Significance:** OHL is considered a "highly suggestive" sign of HIV infection and often predicts the progression to AIDS. * **Histopathology:** Shows hyperkeratosis, parakeratosis, and "ballooning cells" in the upper layers of the epithelium. * **Treatment:** Usually, no specific treatment is required other than initiating **Antiretroviral Therapy (ART)**, which typically leads to the resolution of the lesions as the immune system recovers. * **Differential Diagnosis:** Must be distinguished from **Oral Candidiasis** (which is scrapable and shows pseudohyphae) and **Oral Leukoplakia** (a precancerous lesion associated with tobacco).

Question 172: Segmented RNA is found in which of the following viruses?

A. Influenza virus (Correct Answer)
B. Rabies virus
C. Herpes virus
D. Molluscum contagiosum

Explanation: **Explanation:** The correct answer is **Influenza virus**. The fundamental concept here is the genomic structure of RNA viruses. Most RNA viruses possess a single, continuous strand of RNA; however, a few families possess **segmented genomes**. **1. Why Influenza is correct:** Influenza virus belongs to the **Orthomyxoviridae** family. It contains a single-stranded, negative-sense RNA genome that is divided into **8 segments** (in Influenza A and B) or 7 segments (in Influenza C). This segmentation is clinically critical because it allows for **genetic reassortment** when two different strains infect the same cell, leading to **Antigenic Shift**. This shift results in major changes in surface glycoproteins (Hemagglutinin and Neuraminidase), causing periodic global pandemics. **2. Why other options are incorrect:** * **Rabies virus:** Belongs to the *Rhabdoviridae* family. It has a non-segmented, single-stranded, negative-sense RNA genome (bullet-shaped). * **Herpes virus:** This is a **DNA virus** (Double-stranded, linear DNA). Segmented genomes are a feature of specific RNA viruses, not DNA viruses. * **Molluscum contagiosum:** This belongs to the *Poxviridae* family. Like Herpes, it is a **DNA virus** (Double-stranded, linear DNA) and replicates in the cytoplasm. **High-Yield Clinical Pearls for NEET-PG:** To remember segmented RNA viruses, use the mnemonic **"BOAR"**: * **B**unyaviridae (3 segments) * **O**rthomyxoviridae (8 segments) * **A**renaviridae (2 segments) * **R**eoviridae (10-12 segments – *Note: Reovirus is Double-stranded RNA*) *Key Fact:* Segmented genomes = Potential for **Antigenic Shift** (Reassortment). Non-segmented genomes only undergo **Antigenic Drift** (Point mutations).

Question 173: Which carcinoma is associated with Epstein-Barr virus?

A. Carcinoma of the larynx
B. Carcinoma of the bladder
C. Carcinoma of the nasopharynx (Correct Answer)
D. Carcinoma of the maxilla

Explanation: **Explanation:** **Epstein-Barr Virus (EBV)**, also known as Human Herpesvirus 4 (HHV-4), is a potent oncogenic virus with a strong tropism for B-lymphocytes and epithelial cells. **Why Option C is Correct:** **Nasopharyngeal Carcinoma (NPC)**, specifically the undifferentiated type (WHO Type III), has a definitive causal association with EBV. The virus enters nasopharyngeal epithelial cells via the CD21 receptor (or through fusion mechanisms). Once inside, it establishes a **latency type II pattern**, expressing specific viral oncogenes like **LMP-1** (Latent Membrane Protein-1), which mimics CD40 signaling to promote cell survival and proliferation, leading to malignant transformation. This is particularly prevalent in Southern China and parts of Africa. **Why Other Options are Incorrect:** * **Options A & D (Larynx and Maxilla):** While Head and Neck Squamous Cell Carcinomas (HNSCC) are common, laryngeal and maxillary cancers are primarily linked to tobacco use, alcohol, and occasionally High-Risk HPV (for oropharyngeal sites), but not EBV. * **Option B (Bladder):** Carcinoma of the bladder is strongly associated with smoking, occupational exposure to aromatic amines (aniline dyes), and *Schistosoma haematobium* infection (Squamous cell type), but has no established link to EBV. **High-Yield Clinical Pearls for NEET-PG:** * **EBV-Associated Malignancies:** Burkitt Lymphoma (starry-sky appearance, t(8;14)), Hodgkin Lymphoma (Mixed cellularity), and Gastric Carcinoma (subset). * **Diagnostic Marker:** Elevated titers of **IgA antibodies against Viral Capsid Antigen (VCA)** are used for screening and monitoring recurrence in NPC. * **Non-Malignant EBV Disease:** Infectious Mononucleosis (Glandular fever) and Oral Hairy Leukoplakia (in HIV patients).

Question 174: Which organism's infection presents with clinical features resembling erythroblastosis fetalis?

A. Toxoplasmosis
B. Epstein Barr virus
C. Cytomegalovirus (Correct Answer)
D. Herpes virus

Explanation: **Explanation:** **Cytomegalovirus (CMV)** is the correct answer because its congenital presentation can closely mimic **Erythroblastosis Fetalis** (Rh incompatibility). Both conditions present with a clinical triad of **severe anemia, jaundice, and hepatosplenomegaly**. In severe cases, both can lead to **Hydrops Fetalis** (generalized fetal edema). CMV causes this by infecting the bone marrow and spleen, leading to extramedullary hematopoiesis and hemolysis, which mirrors the hemolytic process seen in Rh isoimmunization. **Analysis of Incorrect Options:** * **Toxoplasmosis:** While it presents with the "classic triad" of chorioretinitis, hydrocephalus, and intracranial calcifications, it does not typically present with the profound hemolytic picture or hydrops characteristic of erythroblastosis fetalis. * **Epstein-Barr Virus (EBV):** EBV is rarely a cause of congenital infections. It typically causes infectious mononucleosis in adolescents and is not associated with the erythroblastosis-like presentation in neonates. * **Herpes Simplex Virus (HSV):** Congenital HSV usually presents with the SEM triad (Skin, Eye, and Mouth vesicles), encephalitis, or disseminated multi-organ failure, rather than isolated hemolytic anemia and hydrops. **NEET-PG High-Yield Pearls:** * **CMV** is the most common intrauterine viral infection. * **Key Diagnostic Feature:** Look for **periventricular calcifications** (vs. diffuse calcifications in Toxoplasmosis). * **Histology:** "Owl’s eye" intranuclear inclusion bodies. * **Clinical Clue:** "Blueberry muffin" spots (extramedullary hematopoiesis) are common in CMV and Rubella. * **Treatment:** Ganciclovir/Valganciclovir is the drug of choice for symptomatic neonatal CMV.

Question 175: Which of the following viruses is known for latency?

A. Herpes Simplex Virus 2 (HSV-2) (Correct Answer)
B. Cytomegalovirus (CMV)
C. Rotavirus
D. Human Immunodeficiency Virus (HIV)

Explanation: ### Explanation **Correct Option: A. Herpes Simplex Virus 2 (HSV-2)** Latency is a hallmark of the **Herpesviridae** family. After the primary infection, the virus remains in a non-replicating state within the host's cells for life. Specifically, **HSV-2** establishes latency in the **sacral ganglia** (S2-S4). Periodic reactivation can occur, triggered by stress, fever, or immunosuppression, leading to recurrent genital herpes. **Analysis of Incorrect Options:** * **B. Cytomegalovirus (CMV):** While CMV is also a member of the Herpesviridae family and *does* exhibit latency (primarily in myeloid progenitor cells and monocytes), in the context of standard NEET-PG questions, HSV is the classic prototype for "latency" due to its well-defined neurotropism and sensory ganglia involvement. However, if this were a "multiple correct" format, CMV would also be technically correct. In single-best-answer formats, HSV is the preferred choice. * **C. Rotavirus:** This is a Reovirus that causes acute gastroenteritis. It does not establish latency; it causes an acute, self-limiting infection and is cleared by the immune system or shed in feces. * **D. HIV:** HIV is a Retrovirus characterized by **persistence**, not classical latency. It undergoes continuous active replication and integrates into the host genome (provirus). While "latent reservoirs" exist in resting T-cells, the clinical hallmark is chronic progression rather than the "dormancy-reactivation" cycle seen in Herpesviruses. **High-Yield Clinical Pearls for NEET-PG:** * **Site of Latency:** HSV-1 (Trigeminal ganglia); HSV-2 (Sacral ganglia); VZV (Dorsal root ganglia); EBV (B-cells). * **Diagnosis:** Tzanck smear showing **Multinucleated Giant Cells** (Cowdry Type A inclusion bodies) is characteristic of HSV and VZV. * **Drug of Choice:** Acyclovir is the mainstay for treating HSV-2 outbreaks and suppressive therapy.

Question 176: Hepatitis A is transmitted by which route?

A. Blood route
B. Inhalation
C. Feco-oral route (Correct Answer)
D. Sexual contact

Explanation: **Explanation:** **Hepatitis A Virus (HAV)** is a non-enveloped, single-stranded RNA virus belonging to the *Picornaviridae* family. The correct answer is the **feco-oral route**, which is the primary mode of transmission. The virus is excreted in the feces of infected individuals; transmission occurs through the ingestion of contaminated water or food (especially raw shellfish) and via person-to-person contact due to poor hand hygiene. **Analysis of Options:** * **Feco-oral route (Correct):** HAV is acid-stable, allowing it to survive the gastric barrier. It replicates in the liver and is shed in high concentrations in bile and stool. * **Blood route (Incorrect):** Unlike Hepatitis B, C, and D, HAV has a very brief period of viremia. Transmission via blood transfusion or needle sticks is extremely rare and not a significant public health route. * **Inhalation (Incorrect):** HAV is not a respiratory pathogen; it does not colonize the respiratory mucosa or spread via droplets. * **Sexual contact (Incorrect):** While transmission can occur during sexual activity (specifically oral-anal contact), this is essentially a variation of the feco-oral route rather than transmission via genital secretions. **High-Yield Clinical Pearls for NEET-PG:** * **Incubation Period:** Short (2–6 weeks). * **Chronicity:** HAV **never** causes chronic infection or a carrier state. * **Diagnosis:** **IgM anti-HAV** is the gold standard for acute infection. **IgG anti-HAV** indicates past infection or vaccination (lifelong immunity). * **Prophylaxis:** Killed vaccine is available. Post-exposure prophylaxis (PEP) involves the vaccine or immunoglobulin (HNIG) depending on the patient's age and health status. * **Epidemiology:** Often associated with overcrowding and poor sanitation; common in travelers to endemic areas.

Question 177: Which of the following is associated with Hepatitis C virus (HCV)?

A. Anti-LKM-1 antibody (Correct Answer)
B. Scleroderma
C. Cryoglobulinemia
D. Polyarteritis nodosa

Explanation: **Explanation:** The correct answer is **Anti-LKM-1 antibody**. **1. Why Anti-LKM-1 is correct:** Anti-Liver Kidney Microsomal type 1 (Anti-LKM-1) antibodies are the hallmark of **Autoimmune Hepatitis (AIH) Type 2**. Interestingly, there is a well-documented molecular mimicry between the Hepatitis C Virus (HCV) and the cytochrome P450 2D6 antigen. Consequently, up to 10% of patients with chronic HCV infection test positive for Anti-LKM-1 antibodies. This makes it a high-yield association for differentiating viral-induced autoimmunity from primary AIH. **2. Analysis of Incorrect Options:** * **Scleroderma:** This is a systemic connective tissue disorder characterized by fibrosis. It is associated with **Anti-centromere** (Limited/CREST) and **Anti-Scl-70** (Diffuse) antibodies, not HCV. * **Cryoglobulinemia:** While **Mixed Cryoglobulinemia (Type II and III)** is strongly associated with HCV, the question asks for the *most specific* immunological marker listed. In many NEET-PG patterns, if both are present, Anti-LKM-1 is tested as the specific antibody association, though Cryoglobulinemia remains the most common extrahepatic manifestation. * **Polyarteritis Nodosa (PAN):** This systemic necrotizing vasculitis is classically associated with **Hepatitis B Virus (HBV)**, not HCV. **3. NEET-PG High-Yield Pearls:** * **HCV & Autoimmunity:** HCV is the "great masquerader" of virology, associated with Lichen Planus, Porphyria Cutanea Tarda, and Membranoproliferative Glomerulonephritis (MPGN). * **LKM Antibody Types:** * **LKM-1:** HCV and AIH Type 2. * **LKM-2:** Drug-induced hepatitis (Ticrynafen). * **LKM-3:** Hepatitis D Virus (HDV). * **HBV vs. HCV:** Remember: **HBV = PAN**; **HCV = Cryoglobulinemia.**

Question 178: Japanese Encephalitis is transmitted by which mosquito species?

A. Culex tritaeniorhynchus
B. Culex vishnui
C. Culex pseudovishnui
D. All of the above (Correct Answer)

Explanation: **Explanation:** Japanese Encephalitis (JE) is the leading cause of viral encephalitis in Asia, caused by a Flavivirus. It is a zoonotic disease where the virus is maintained in an **enzootic cycle** involving mosquitoes as vectors and pigs or water birds (Ardeid birds) as reservoirs. **Why "All of the above" is correct:** The primary vectors for Japanese Encephalitis are mosquitoes of the **Culex vishnui subgroup**. This subgroup consists of three main species that are all competent vectors: 1. **Culex tritaeniorhynchus:** This is the **most important and principal vector** across most of Asia, including India. It breeds predominantly in stagnant water like rice fields. 2. **Culex vishnui:** A significant vector that contributes to transmission in rural areas. 3. **Culex pseudovishnui:** Also a proven vector within the same subgroup. Since all three species belong to the primary vector group responsible for the transmission of the JE virus to humans, option D is the correct choice. **High-Yield Clinical Pearls for NEET-PG:** * **Reservoirs:** Pigs are considered "amplifier hosts" (they develop high viremia), while Ardeid birds (herons, egrets) are the natural reservoir hosts. * **Dead-end Hosts:** Humans and horses are "dead-end hosts" because they do not develop sufficient viremia to infect feeding mosquitoes. * **Seasonality:** Transmission usually peaks during the rainy season and pre-harvest periods (due to rice field irrigation). * **Diagnosis:** The investigation of choice is **MAC-ELISA** to detect IgM antibodies in CSF or serum. * **Vaccination:** The **SA-14-14-2** (live attenuated) vaccine is commonly used in the Universal Immunization Programme (UIP) in endemic areas of India.

Question 179: What are bacteriophages?

A. Bacteria that infect viruses
B. Viruses that infect bacteria (Correct Answer)
C. Viruses that infect protozoa
D. Bacteria that infect protozoa

Explanation: **Explanation:** **Bacteriophages** (often simply called "phages") are obligate intracellular **viruses** that specifically target and replicate within **bacteria**. The term literally translates to "bacteria eater" (from the Greek *phagein*, meaning "to devour"). They function by attaching to specific receptors on the bacterial cell wall, injecting their genetic material (DNA or RNA), and hijacking the host’s metabolic machinery to produce new viral particles. **Analysis of Options:** * **Option B (Correct):** Bacteriophages are viral entities. They play a crucial role in bacterial genetics through **transduction**, where they transfer DNA from one bacterium to another, often spreading antibiotic resistance or virulence factors. * **Option A:** This is biologically impossible; bacteria are complex cellular organisms and cannot "infect" a virus, which is a non-cellular genetic entity. * **Options C & D:** Viruses or bacteria that infect protozoa are distinct categories (e.g., *Acanthamoeba polyphaga mimivirus*). Bacteriophages are strictly host-specific to bacteria. **High-Yield Clinical Pearls for NEET-PG:** 1. **Life Cycles:** Phages exhibit two main cycles: **Lytic** (virulent phages cause cell lysis) and **Lysogenic** (temperate phages integrate their DNA into the bacterial chromosome as a **prophage**). 2. **Lysogenic Conversion:** This is a high-yield concept where a non-pathogenic bacterium becomes pathogenic after being infected by a temperate phage. Examples include: * *Corynebacterium diphtheriae* (Toxin production via **Beta-phage**) * *Vibrio cholerae* (CTX phage) * *Streptococcus pyogenes* (Erythrogenic toxin) * *Clostridium botulinum* (Botulinum toxin) 3. **Phage Typing:** Used in epidemiology to track the source of outbreaks (e.g., *Staphylococcus aureus* or *Salmonella Typhi*) by identifying the specific phage strains that lyse the bacteria.

Question 180: A VDRL reactive mother gave birth to an infant. All of the following would help in determining the risk of transmission to the infant, EXCEPT?

A. TPHA test on the serum sample of the mother
B. TPHA test on the serum sample of the infant (Correct Answer)
C. VDRL on the paired serum sample of the infant and mother
D. Time interval between the treatment of the mother and her delivery

Explanation: ### Explanation The diagnosis of congenital syphilis is challenging because maternal antibodies cross the placenta, making it difficult to distinguish between an infant's active infection and passive immunity. **Why Option B is the Correct Answer:** TPHA (Treponema Pallidum Haemagglutination Assay) is a **treponemal test** that detects IgG antibodies. Since maternal IgG antibodies freely cross the placenta and can persist in the infant’s circulation for up to 12–15 months, a positive TPHA in an infant does not differentiate between a true infection and passively acquired maternal antibodies. Therefore, it is **not helpful** in determining the risk of transmission or diagnosing active congenital syphilis. **Analysis of Other Options:** * **Option A (TPHA on mother):** Confirms that the mother’s reactive VDRL is due to syphilis and not a biological false positive (BFP). If the mother is TPHA negative, there is no risk of transmission. * **Option C (VDRL on paired samples):** A quantitative VDRL is crucial. A **four-fold increase** in the infant’s titer compared to the mother’s titer is highly suggestive of active congenital infection. * **Option D (Treatment timing):** The risk of transmission is highest if the mother is untreated or treated less than **4 weeks before delivery**. Adequate treatment of the mother significantly reduces the risk to the infant. ### Clinical Pearls for NEET-PG * **Screening vs. Confirmation:** VDRL/RPR are used for screening and monitoring treatment; TPHA/FTA-ABS are used for confirmation. * **Diagnosis of Choice:** The most specific serological test for diagnosing congenital syphilis in an infant is the **IgM FTA-ABS** or **IgM ELISA**, as IgM does not cross the placenta. * **Hutchinson’s Triad:** Interstitial keratitis, sensorineural hearing loss (8th nerve deafness), and Hutchinson’s teeth. * **Early Sign:** Syphilitic rhinitis (snuffles) is often the earliest clinical sign of congenital syphilis.

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