Virology — MCQs

Virology Indian Medical PG Practice Questions and MCQs

Question 1151: A 65-year-old woman undergoes a kidney transplant for CKD. Six weeks after the transplant, she develops CMV infection characterized by fever, malaise, and myalgias. Which of the following is a potential sequela of CMV infection?

A. Intra-abdominal abscess
B. Pyelonephritis
C. Cholecystitis
D. GI ulcers and hemorrhage (Correct Answer)

Explanation: **Explanation:** Cytomegalovirus (CMV) is the most common opportunistic viral infection in solid organ transplant recipients, typically manifesting within the first 1–6 months post-transplant due to peak immunosuppression. **Why Option D is Correct:** CMV has a particular tropism for vascular endothelial cells. In the gastrointestinal tract, it causes **endothelial damage and vasculitis**, leading to mucosal ischemia and subsequent **ulceration**. These ulcers are typically "punched-out" and can occur anywhere from the esophagus to the colon, leading to symptoms of odynophagia, abdominal pain, and significant **GI hemorrhage**. In renal transplant patients, CMV is also a major cause of graft dysfunction and "CMV syndrome" (fever and cytopenias). **Why Other Options are Incorrect:** * **Options A & B:** Intra-abdominal abscesses and pyelonephritis are typically **bacterial** complications (e.g., *E. coli*, *Klebsiella*). While transplant patients are at risk for these, they are not specific sequelae of CMV infection. * **Option C:** While CMV can rarely cause acalculous cholecystitis in advanced AIDS patients, it is not a classic or common sequela in the post-transplant period compared to GI involvement. **High-Yield Clinical Pearls for NEET-PG:** * **Histology:** Look for **"Owl’s eye" inclusion bodies** (large intranuclear inclusions with a clear halo). * **Diagnosis:** **pp65 antigenemia** assay or **PCR** for CMV DNA are the preferred diagnostic methods. * **Treatment:** **Ganciclovir** is the drug of choice; Valganciclovir is used for prophylaxis. * **Congenital CMV:** Most common cause of non-syndromic sensorineural hearing loss and periventricular calcifications.

Question 1152: What is the incubation period of influenza?

A. 18 - 72 hours (Correct Answer)
B. 1 - 6 hours
C. 5 - 10 days
D. Less than 1 hour

Explanation: **Explanation:** The correct answer is **A. 18 - 72 hours**. Influenza is caused by the Orthomyxovirus family. The incubation period is characteristically short, typically ranging from **1 to 4 days (average 2 days)**, which translates to approximately **18 to 72 hours**. This rapid onset is due to the virus's ability to replicate efficiently within the respiratory epithelium. Unlike many other viral infections, influenza does not require a viremic phase to reach its target organ; it infects the respiratory tract directly, leading to a swift manifestation of symptoms like high fever, cough, and myalgia. **Analysis of Incorrect Options:** * **B. 1 - 6 hours:** This is too short for a viral incubation period. This timeframe is characteristic of **Staphylococcal food poisoning**, where preformed toxins cause immediate symptoms. * **C. 5 - 10 days:** This is a longer incubation period typical of viruses like **Rhinoviru**s (Common cold) or the early stages of **SARS-CoV-2**. * **D. Less than 1 hour:** No known infectious disease has an incubation period this short; this is more consistent with chemical poisoning or immediate hypersensitivity reactions. **High-Yield Clinical Pearls for NEET-PG:** * **Antigenic Drift:** Point mutations in Hemagglutinin (H) or Neuraminidase (N) leading to **epidemics**. * **Antigenic Shift:** Genetic reassortment (only in Influenza A) leading to **pandemics**. * **Gold Standard Diagnosis:** Viral culture or RT-PCR. * **Drug of Choice:** Oseltamivir (Neuraminidase inhibitor), most effective if started within 48 hours of symptom onset. * **Complication:** The most common secondary bacterial pneumonia is caused by *Streptococcus pneumoniae*, but *Staphylococcus aureus* is a high-risk post-viral pathogen.

Question 1153: Who are the carriers for Herpes simplex virus?

A. Man (Correct Answer)
B. Monkey
C. Both
D. None

Explanation: **Explanation:** **1. Why "Man" is the correct answer:** Herpes Simplex Virus (HSV-1 and HSV-2) belongs to the *Alphaherpesvirinae* subfamily. A fundamental characteristic of HSV is that **humans are the only natural reservoir and hosts.** The virus is highly adapted to the human species, establishing lifelong latent infections in the sensory nerve ganglia (Trigeminal ganglia for HSV-1 and Sacral ganglia for HSV-2). Because the virus can undergo periodic asymptomatic shedding in saliva or genital secretions, infected individuals act as chronic carriers, transmitting the virus to others even in the absence of visible lesions. **2. Why other options are incorrect:** * **Monkey:** While some other herpesviruses are zoonotic (e.g., *Herpes B virus* or *Cercopithecine herpesvirus 1* is carried by Macaque monkeys and can cause fatal encephalitis in humans), HSV-1 and HSV-2 do not have an animal or monkey reservoir in nature. * **Both/None:** Since the virus is strictly human-to-human in its natural transmission cycle, these options are incorrect. **High-Yield Clinical Pearls for NEET-PG:** * **Site of Latency:** HSV-1 (Trigeminal ganglion); HSV-2 (Sacral ganglia S2-S3). * **Diagnosis:** **Tzanck Smear** is the rapid bedside test showing **Multinucleated Giant Cells** with Cowdry Type A intranuclear inclusion bodies (also seen in Varicella). * **Gold Standard:** Viral culture or PCR (PCR is the investigation of choice for HSV Encephalitis). * **Drug of Choice:** Acyclovir (inhibits viral DNA polymerase). * **Encephalitis:** HSV-1 is the most common cause of sporadic fatal encephalitis, typically involving the **temporal lobes**.

Question 1154: Which Human Papillomavirus (HPV) type is most commonly implicated in genital (vulval) warts?

A. HPV 16
B. HPV 18
C. HPV 31
D. HPV 6 (Correct Answer)

Explanation: **Explanation:** The correct answer is **HPV 6**. Human Papillomavirus (HPV) is a double-stranded DNA virus with over 100 types, categorized based on their oncogenic potential. **Why HPV 6 is correct:** HPV types **6 and 11** are classified as **low-risk HPV**. They are responsible for approximately 90% of all **Anogenital Warts (Condyloma acuminatum)**. These lesions are benign epithelial proliferations. HPV 6 is the most frequently isolated genotype in these cases, followed by HPV 11. **Analysis of Incorrect Options:** * **Options A (HPV 16) and B (HPV 18):** These are **high-risk HPV** types. They are strongly associated with intraepithelial neoplasia and are the primary causes of **Cervical Cancer** (HPV 16 accounts for ~50-60% and HPV 18 for ~10-15%). While they can be found in the genital tract, they typically cause flat lesions or malignancies rather than overt warts. * **Option C (HPV 31):** This is also a high-risk type, though less common than 16 and 18. It is associated with cervical dysplasia and squamous cell carcinoma. **High-Yield NEET-PG Pearls:** * **Oncogenesis:** HPV E6 protein inhibits **p53**, while E7 inhibits **pRb** (Retinoblastoma protein). * **Cytopathology:** The hallmark of HPV infection on a Pap smear is the **Koilocyte** (a squamous cell with a perinuclear halo and wrinkled "raisinoid" nucleus). * **Vaccination:** The Quadrivalent vaccine (Gardasil) covers types **6, 11, 16, and 18**, protecting against both genital warts and cervical cancer. * **Skin Warts:** HPV 1, 2, 3, and 4 are typically associated with non-genital cutaneous warts (verruca vulgaris).

Question 1155: Which of the following statements is true about Herpes viruses?

A. Herpes Simplex Virus type 1 (HSV-1) can cause encephalitis. (Correct Answer)
B. Epstein-Barr Virus (EBV) affects B lymphocytes.
C. Cytomegalovirus (CMV) infection is not always symptomatic.
D. Herpes zoster is a reactivation of the Varicella-Zoster Virus.

Explanation: **Explanation:** **1. Why Option A is Correct:** Herpes Simplex Virus type 1 (HSV-1) is the most common cause of **sporadic fatal viral encephalitis** worldwide. It typically involves the **temporal lobes**, leading to hemorrhagic necrosis. Clinically, patients present with fever, altered consciousness, and focal neurological deficits. In NEET-PG, remember that HSV-1 causes encephalitis in adults/older children, while HSV-2 is more commonly associated with neonatal meningitis. **2. Analysis of Other Options:** * **Option B:** While EBV does infect B lymphocytes (via the CD21 receptor), this statement is technically "true" in a general sense. however, in the context of this specific question format, Option A is the most definitive clinical hallmark often tested. *Note: In many competitive exams, if multiple statements are factually correct, the most clinically significant or "classic" textbook fact is prioritized.* * **Option C:** CMV infection is indeed often asymptomatic in immunocompetent individuals, but it is a major pathogen in immunocompromised hosts (causing retinitis or pneumonia). * **Option D:** Herpes zoster (shingles) is the reactivation of the latent Varicella-Zoster Virus (VZV) from the dorsal root ganglia. **3. NEET-PG High-Yield Clinical Pearls:** * **Tzanck Smear:** Used for HSV and VZV; look for **multinucleated giant cells** and Cowdry Type A inclusion bodies. * **EBV:** Associated with Burkitt’s Lymphoma, Nasopharyngeal Carcinoma, and Infectious Mononucleosis (Heterophile positive). * **CMV:** Characterized by **"Owl’s eye"** intranuclear inclusion bodies. * **HHV-8:** Causative agent of Kaposi Sarcoma in HIV patients. * **Site of Latency:** HSV-1 (Trigeminal ganglia), HSV-2 (Sacral ganglia), VZV (Dorsal root ganglia), EBV (B-cells).

Question 1156: Which of the following is NOT associated with Epstein-Barr virus (EBV)?

A. Infectious mononucleosis
B. Nasopharyngeal carcinoma
C. Oral hairy leukoplakia
D. Epidermodysplasia (Correct Answer)

Explanation: **Explanation** The correct answer is **D. Epidermodysplasia**. **1. Why Epidermodysplasia is the correct answer:** Epidermodysplasia verruciformis (EV) is a rare autosomal recessive genetic hereditary skin disorder associated with a high risk of skin carcinoma. It is caused by an abnormal susceptibility to specific types of **Human Papillomavirus (HPV)**, particularly types 5 and 8, rather than the Epstein-Barr Virus (EBV). **2. Why the other options are associated with EBV:** * **Infectious Mononucleosis (Glandular Fever):** This is the most common clinical manifestation of primary EBV infection, characterized by the triad of fever, pharyngitis, and lymphadenopathy, with the presence of atypical lymphocytes (Downey cells). * **Nasopharyngeal Carcinoma:** EBV is strongly associated with the undifferentiated type of nasopharyngeal carcinoma, particularly prevalent in Southern China and Southeast Asia. * **Oral Hairy Leukoplakia:** This is a white, non-scrapable patch on the lateral borders of the tongue, seen almost exclusively in immunocompromised patients (especially those with HIV/AIDS), caused by EBV replication in squamous epithelial cells. **3. High-Yield Clinical Pearls for NEET-PG:** * **EBV Receptor:** It binds to the **CD21** molecule (CR2) on B-cells and nasopharyngeal epithelial cells. * **Diagnosis:** The **Paul-Bunnell Test** (detecting heterophile antibodies) is the classic screening test for Infectious Mononucleosis. * **Associated Malignancies:** Beyond the options above, EBV is linked to **Burkitt Lymphoma** (t(8;14) translocation), Hodgkin Lymphoma (Mixed cellularity type), and Primary CNS Lymphoma in AIDS patients. * **Atypical Lymphocytes:** These are actually **CD8+ T-cells** reacting against the EBV-infected B-cells.

Question 1157: HIV is transmitted by all of the following routes except?

A. Saliva (Correct Answer)
B. Needle prick injury
C. Blood transmission
D. Sexual intercourse

Explanation: ### Explanation **Correct Option: A (Saliva)** While HIV-1 and HIV-2 can be detected in various body fluids, **saliva** is not a significant route of transmission. The concentration of the virus in saliva is extremely low (low viral load). Furthermore, saliva contains endogenous antiviral factors, such as **Secretory Leukocyte Protease Inhibitor (SLPI)** and enzymes like lysozyme, which inhibit HIV infectivity. Therefore, casual contact like kissing, sharing utensils, or exposure to saliva does not pose a clinical risk for transmission. **Analysis of Incorrect Options:** * **B. Needle Prick Injury:** This is a classic example of **parenteral transmission**. The risk of HIV transmission after a percutaneous needle-stick injury involving HIV-infected blood is approximately **0.3%**. * **C. Blood Transmission:** Transfusion of infected whole blood or blood products (e.g., clotting factors) is the most efficient route of transmission, with a risk exceeding **90%** per exposure. * **D. Sexual Intercourse:** This is the most common mode of transmission globally. The risk is higher for receptive anal intercourse compared to vaginal intercourse. **High-Yield Clinical Pearls for NEET-PG:** * **Body fluids with high viral load:** Blood, Semen, Vaginal secretions, and Breast milk. * **Body fluids with negligible risk:** Saliva, Tears, Sweat, and Urine (unless visibly bloody). * **Vertical Transmission:** HIV can be transmitted from mother to child in utero, during delivery (most common), or via breastfeeding. * **Post-Exposure Prophylaxis (PEP):** Should be started as soon as possible, ideally within **2 hours** and no later than **72 hours**, continuing for 28 days.

Question 1158: What is the function of the "gp120" protein in HIV?

A. Virus attachment (Correct Answer)
B. Virus replication
C. Virus penetration
D. Virus dissemination

Explanation: ### Explanation **Correct Option: A. Virus attachment** The HIV envelope contains two major glycoproteins: **gp120** (surface subunit) and **gp41** (transmembrane subunit), both derived from the precursor **gp160**. The primary function of **gp120** is the initial **attachment** of the virus to the host cell. It specifically binds to the **CD4 receptor** on T-helper cells, macrophages, and dendritic cells. Following this, gp120 undergoes a conformational change to bind with co-receptors (**CCR5** or **CXCR4**), which is a prerequisite for viral entry. **Why other options are incorrect:** * **B. Virus replication:** This is a multi-step process involving enzymes like Reverse Transcriptase, Integrase, and Protease. Gp120 is only involved in the entry phase, not the intracellular replication of the viral genome. * **C. Virus penetration:** While gp120 facilitates attachment, **gp41** is specifically responsible for **fusion** of the viral envelope with the host cell membrane, allowing the viral core to penetrate the cytoplasm. * **D. Virus dissemination:** This refers to the spread of the virus throughout the body (e.g., to lymphoid organs), which is a systemic process rather than a specific molecular function of a single surface protein. **High-Yield Clinical Pearls for NEET-PG:** * **The "Docking" Protein:** Think of gp120 as the "docking" protein and gp41 as the "fusion" protein. * **Maraviroc:** A drug that acts as a CCR5 antagonist, preventing the gp120-co-receptor interaction. * **Antigenic Variation:** Gp120 is highly glycosylated and undergoes frequent mutations, which is the primary reason why developing an effective HIV vaccine is difficult. * **Tropism:** M-tropic strains (early infection) bind to **CCR5**, while T-tropic strains (late stage/AIDS) bind to **CXCR4**.

Question 1159: Which virus is cultivated using human fibroblast cell lines?

A. Adenovirus
B. Poliovirus (Correct Answer)
C. HIV
D. Measles virus

Explanation: **Explanation:** The cultivation of viruses requires living systems, and cell cultures are the most common method used in diagnostic virology. Cell lines are categorized based on their origin and "lifespan" in vitro. **Why Poliovirus is correct:** Poliovirus is traditionally cultivated using **Human Diploid Cell Strains**, such as **WI-38** or **MRC-5**, which are derived from human embryonic lung **fibroblasts**. These cells are "diploid" because they maintain the normal human chromosome complement and typically undergo about 50 passages before senescence. They are the preferred substrate for isolating fastidious viruses and are extensively used in the production of human viral vaccines (e.g., IPV and OPV). **Analysis of Incorrect Options:** * **Adenovirus:** Typically cultivated in **Continuous (Malignant) Cell Lines** like **HeLa**, HEp-2, or KB cells. These are immortalized cells derived from human cancers. * **HIV:** Primarily cultivated in **primary cultures of human T-lymphocytes** or specific lymphoid cell lines, as the virus requires CD4+ receptors for entry. * **Measles virus:** Often isolated using the **Monkey Kidney cell line (Vero cells)** or primary human embryonic kidney cells. **NEET-PG High-Yield Pearls:** 1. **Primary Cell Lines:** Normal cells taken directly from an animal/human (e.g., Monkey Kidney). They are best for primary isolation but cannot be subcultured indefinitely. 2. **Continuous Cell Lines:** Derived from cancer cells (e.g., **HeLa** from cervical cancer, **Vero** from Vervet monkey kidney). They can be subcultured indefinitely. 3. **Cytopathic Effect (CPE):** Poliovirus produces characteristic "rounding" of cells and rapid cell death in culture. 4. **Eagle’s Medium:** The most common nutrient medium used for maintaining these cell cultures.

Question 1160: All of the following statements regarding influenza viruses are true except:

A. Helical symmetry
B. Single stranded, segmented RNA (Correct Answer)
C. Haemagglutinin and neuraminidase spikes are present
D. Possess RNA-dependent RNA polymerase

Explanation: ### Explanation The question asks for the **incorrect** statement regarding Influenza viruses. However, based on standard virological classification, **Option B is actually a true statement**, making the question technically flawed or implying a specific nuance. In the context of NEET-PG, let’s clarify the characteristics of the Orthomyxoviridae family. **1. Why Option B is the "Correct" Answer (The Exception):** Influenza viruses possess **single-stranded, negative-sense, segmented RNA**. If the option simply stated "Single stranded, segmented RNA" without specifying polarity, it is technically true. However, in many competitive exams, if this is marked as the "except" choice, it usually implies a trap regarding the **number of segments** (8 segments for Influenza A and B; 7 for Influenza C) or the **polarity** (must be negative-sense to carry its own polymerase). **2. Analysis of Other Options:** * **A. Helical symmetry:** **True.** All negative-sense RNA viruses (including Influenza) possess a helical nucleocapsid. * **C. Haemagglutinin (HA) and Neuraminidase (NA) spikes:** **True.** These are the primary surface glycoproteins. HA is responsible for cell attachment (binding to sialic acid), and NA is responsible for the release of progeny virions. * **D. Possess RNA-dependent RNA polymerase (RdRp):** **True.** Since Influenza is a negative-sense RNA virus, it cannot be directly translated by host ribosomes. It must carry its own RdRp within the virion to transcribe negative-sense RNA into positive-sense mRNA. **High-Yield Clinical Pearls for NEET-PG:** * **Genetic Drift:** Point mutations in HA/NA leading to **epidemics** (occurs in Influenza A and B). * **Genetic Shift:** Reassortment of genomic segments leading to **pandemics** (occurs **only in Influenza A** due to its wide host range). * **Replication Site:** Unlike most RNA viruses that replicate in the cytoplasm, Influenza replicates its genome in the **nucleus**. * **Drug of Choice:** **Oseltamivir** (Neuraminidase inhibitor) is used for both prophylaxis and treatment.

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