Virology — MCQs

Virology Indian Medical PG Practice Questions and MCQs

Question 431: Which of the following infections is not transmitted vertically?

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

Explanation: **Explanation:** The concept of "vertical transmission" refers specifically to the passage of a pathogen from mother to fetus **in utero** (transplacentally). While many infections can be passed from mother to child, the timing and route define the classification. **Why HSV is the correct answer:** Herpes Simplex Virus (HSV) is primarily transmitted **perinatally** (during delivery) through direct contact with infected maternal secretions in the birth canal. It is rarely transmitted vertically (transplacentally). In the context of standard NEET-PG questions, HSV is classified as a perinatal infection rather than a classic vertical/congenital infection. **Analysis of Incorrect Options:** * **Cytomegalovirus (CMV):** The most common cause of congenital infection worldwide. It readily crosses the placenta (vertical transmission) and can cause sensorineural hearing loss and periventricular calcifications. * **Toxoplasmosis:** Caused by *Toxoplasma gondii*, this parasite is a classic member of the TORCH complex, transmitted transplacentally if the mother acquires a primary infection during pregnancy. * **HIV:** Can be transmitted vertically (transplacental), though it is also transmitted perinatally and via breast milk. Without intervention, the risk of vertical transmission is significant. **Clinical Pearls for NEET-PG:** * **TORCH Complex:** Remember the mnemonic for vertical transmission: **T**oxoplasmosis, **O**thers (Syphilis, Parvovirus B19, Zika), **R**ubella, **C**MV, **H**epatitis B/HIV. * **HSV Management:** To prevent perinatal transmission, a Cesarean section is indicated if active genital lesions are present at the time of labor. * **CMV:** Look for "Owl’s eye" inclusion bodies in histopathology. * **Toxoplasmosis:** Classic triad includes Chorioretinitis, Hydrocephalus, and Intracranial calcifications.

Question 432: Hepatitis B virus (HBV) is associated with all of the following except?

A. Hepatic cancer
B. Chronic hepatitis
C. Hepatic adenoma (Correct Answer)
D. Cirrhosis

Explanation: **Explanation:** The correct answer is **C. Hepatic adenoma**. **1. Why Hepatic Adenoma is the correct answer:** Hepatic adenoma is a **benign** liver tumor primarily associated with **oral contraceptive pill (OCP) use**, anabolic steroid use, or glycogen storage diseases. It is not caused by viral infections. Hepatitis B Virus (HBV) is a known oncogenic virus that integrates into the host genome, leading to malignant transformation rather than benign adenomatous growth. **2. Analysis of Incorrect Options:** * **Hepatic Cancer (Hepatocellular Carcinoma - HCC):** HBV is a major risk factor for HCC. The HBx protein acts as a transcriptional transactivator that disrupts cell cycle control and inhibits p53 (a tumor suppressor gene), directly promoting malignancy. * **Chronic Hepatitis:** Approximately 5–10% of adults and up to 90% of infected neonates fail to clear the surface antigen (HBsAg) within 6 months, leading to chronic hepatitis. * **Cirrhosis:** Chronic inflammation and immune-mediated destruction of hepatocytes lead to extensive fibrosis and regenerative nodules, culminating in cirrhosis. HBV is one of the leading causes of cirrhosis worldwide. **3. NEET-PG High-Yield Pearls:** * **HBV Genome:** It is a partially double-stranded circular DNA virus (Hepadnaviridae). * **Oncogenesis:** HBV can cause HCC **without** preceding cirrhosis (unlike HCV, where cirrhosis is usually a prerequisite). * **Extrahepatic Manifestations:** HBV is strongly associated with **Polyarteritis Nodosa (PAN)** and Membranous Glomerulonephritis. * **Ground Glass Hepatocytes:** A classic histological finding in chronic HBV infection due to the accumulation of HBsAg in the endoplasmic reticulum.

Question 433: Which bacterium is known to survive in alkaline media?

A. E. coli
B. Shigella
C. Vibrio (Correct Answer)
D. Salmonella

Explanation: **Explanation:** The correct answer is **Vibrio cholerae**. This bacterium is a classic example of an **alkaliphile**, meaning it thrives in environments with a high pH (alkaline). **1. Why Vibrio is correct:** *Vibrio cholerae* grows optimally at a pH of **8.2 to 8.9**, though it can survive in environments with a pH as high as 9.5. This physiological trait is exploited in clinical microbiology to create **selective media** (e.g., **TCBS Agar**—Thiosulfate Citrate Bile Salts Sucrose agar) and **enrichment media** (e.g., **Alkaline Peptone Water** with pH 8.6). The alkaline environment inhibits the growth of most other intestinal commensals, allowing *Vibrio* to flourish. **2. Why other options are incorrect:** * **E. coli, Shigella, and Salmonella:** These are members of the *Enterobacteriaceae* family. While they can tolerate a range of pH levels, they generally prefer a neutral pH (7.2–7.4). Unlike *Vibrio*, they are highly sensitive to alkaline conditions and are easily inhibited by the high pH used in *Vibrio*-specific media. Furthermore, *Vibrio* is uniquely sensitive to stomach acid (acid-labile), which is why a high infectious dose is required unless the patient is taking antacids. **High-Yield Clinical Pearls for NEET-PG:** * **Enrichment Media for Vibrio:** Alkaline Peptone Water (APW) and Monsur’s Tellurite Taurocholate Gelatin Phosphate (TTGP). * **Selective Media:** TCBS (produces yellow colonies due to sucrose fermentation). * **Transport Media:** Venkatraman-Ramakrishnan (VR) medium and Cary-Blair medium. * **The "String Test":** Used to identify *Vibrio* species; colonies emulsified in 0.5% sodium deoxycholate become mucoid and form a "string."

Question 434: Which of the following statements about rabies virus is incorrect?

A. It is a DNA virus. (Correct Answer)
B. Vaccine virus has a fixed incubation period.
C. Negri bodies are found in the hippocampus.
D. All bites on fingers with laceration are class three injuries.

Explanation: **Explanation:** **1. Why Option A is the Correct Answer (The Incorrect Statement):** Rabies virus belongs to the family **Rhabdoviridae** and the genus *Lyssavirus*. It is a **single-stranded, negative-sense RNA virus**, not a DNA virus. It is characterized by its distinct bullet-shaped morphology and an envelope covered with glycoprotein spikes. **2. Analysis of Other Options:** * **Option B:** In rabies research, "Street virus" (found in nature) has a highly variable incubation period. However, the **"Fixed virus"** (used for vaccine production, derived by repeated serial passage in brains of rabbits) has a shortened and **fixed incubation period** (usually 4–6 days). * **Option C:** **Negri bodies** are pathognomonic intracytoplasmic eosinophilic inclusion bodies. They are most commonly and characteristically found in the **Pyramidal cells of the Hippocampus (Ammon’s horn)** and Purkinje cells of the cerebellum. * **Option D:** According to WHO and National guidelines, **Category III** (High risk) exposures include single or multiple transdermal bites or scratches, licks on broken skin, or contamination of mucous membranes with saliva. Any bite on the **fingers/hands** (highly innervated areas) or lacerated wounds are automatically classified as Class III, requiring both vaccine and Rabies Immunoglobulin (RIG). **Clinical Pearls for NEET-PG:** * **Shape:** Bullet-shaped virus. * **Genome:** ssRNA, linear, non-segmented, negative sense. * **Centripetal spread:** Moves via retrograde axonal transport to the CNS. * **Hydrophobia:** Occurs due to forceful spasms of the diaphragm and accessory respiratory muscles when attempting to swallow. * **Diagnosis:** Direct Fluorescent Antibody (DFA) test on skin biopsy (from the nape of the neck) or corneal impression is a gold standard intra-vitam test.

Question 435: Which of the following is an RNA virus?

A. Hepatitis B virus
B. Parainfluenza virus (Correct Answer)
C. Adenoviruses
D. Herpes simplex virus

Explanation: **Explanation:** The classification of viruses into DNA or RNA genomes is a fundamental high-yield topic for NEET-PG. **Correct Option: B. Parainfluenza virus** The Parainfluenza virus belongs to the **Paramyxoviridae** family. All members of this family (including Measles, Mumps, and RSV) are **enveloped, single-stranded, negative-sense RNA viruses**. They replicate in the cytoplasm and are characterized by the presence of an RNA-dependent RNA polymerase. **Incorrect Options:** * **A. Hepatitis B virus:** This is a member of the **Hepadnaviridae** family. It is a partially double-stranded **DNA virus**. It is unique because it uses reverse transcriptase during its replication cycle, despite being a DNA virus. * **C. Adenoviruses:** These are **non-enveloped, double-stranded linear DNA viruses**. They are common causes of pharyngoconjunctival fever and hemorrhagic cystitis. * **D. Herpes simplex virus:** Belonging to the **Herpesviridae** family, these are **enveloped, double-stranded linear DNA viruses**. This family also includes EBV, CMV, and VZV. **NEET-PG Clinical Pearls:** 1. **Mnemonic for DNA Viruses:** "**HHAPPPPy**" (Hepadna, Herpes, Adeno, Pox, Parvo, Papilloma, Polyoma). Note that **Parvo** is the only single-stranded DNA virus. 2. **Parainfluenza Clinical Link:** It is the most common cause of **Croup (Laryngotracheobronchitis)**, characterized by a barking cough and the "Steeple sign" on X-ray. 3. All RNA viruses replicate in the **cytoplasm**, EXCEPT Orthomyxoviruses (Influenza) and Retroviruses (HIV), which involve the nucleus.

Question 436: Which virus from the following can be easily detected by CSF culture?

A. Cytomegalovirus (CMV) (Correct Answer)
B. Echovirus
C. Coxsackievirus
D. Herpes Simplex Virus (HSV)

Explanation: **Explanation:** The correct answer is **Cytomegalovirus (CMV)**. While viral isolation from Cerebrospinal Fluid (CSF) is generally difficult for most neurotropic viruses, CMV is an exception in specific clinical contexts. **1. Why CMV is the correct answer:** In patients with CMV-related neurological diseases (such as ventriculoencephalitis or polyradiculopathy, often seen in advanced HIV/AIDS), the viral load in the CSF is typically very high. CMV can be isolated using conventional cell culture or the **Shell Vial culture technique**, which provides rapid results (24–48 hours) by detecting immediate-early antigens. While PCR is now the gold standard for diagnosis due to its speed and sensitivity, CMV remains the most "culturable" virus from CSF among the options provided. **2. Why other options are incorrect:** * **Echovirus & Coxsackievirus (Enteroviruses):** These are the most common causes of viral meningitis. While they can be grown in suckling mice or specific cell lines (like Monkey Kidney cells), their recovery rate from CSF is significantly lower than from stool or throat swabs. PCR is the preferred diagnostic method. * **Herpes Simplex Virus (HSV):** HSV-1 (Encephalitis) and HSV-2 (Meningitis) are notoriously difficult to culture from CSF. The sensitivity of CSF culture for HSV is **less than 5%**. Diagnosis relies almost exclusively on CSF PCR. **High-Yield Clinical Pearls for NEET-PG:** * **Gold Standard for Viral CNS Infections:** CSF PCR has replaced culture for almost all viral CNS pathogens. * **CMV Histology:** Look for **"Owl’s Eye"** intranuclear inclusion bodies. * **Enterovirus:** Most common cause of "Aseptic Meningitis." * **HSV Encephalitis:** Characterized by hemorrhagic necrosis of the **temporal lobes**; CSF shows increased RBCs and xanthochromia.

Question 437: Papillomavirus has been found in all of the following lesions except?

A. Oral papillomas
B. Verruca vulgaris of the oral mucosa
C. Condyloma acuminatum
D. Condyloma latum (Correct Answer)

Explanation: **Explanation:** The correct answer is **Condyloma latum** because it is a clinical manifestation of **Secondary Syphilis**, caused by the spirochete *Treponema pallidum*, not Human Papillomavirus (HPV). **1. Why Condyloma latum is the correct answer:** Condyloma lata are flat, moist, wart-like papules typically found in intertriginous areas (like the anogenital region) during the secondary stage of syphilis. They are highly infectious and contain a high load of spirochetes. In contrast, HPV-related lesions are usually more "verrucous" or cauliflower-like in appearance. **2. Why the other options are incorrect:** * **Oral papillomas:** These are benign epithelial tumors caused by HPV types 6 and 11. * **Verruca vulgaris:** Also known as common warts, these are caused by HPV (primarily types 2 and 4) and can occur on the oral mucosa. * **Condyloma acuminatum:** These are genital warts caused by low-risk HPV types 6 and 11. They are characterized by a "cauliflower-like" appearance and koilocytic changes on histology. **High-Yield Clinical Pearls for NEET-PG:** * **The "L" Rule:** Condyloma **L**atum = **L**ues (Syphilis); Condyloma **A**cuminatum = **A**PV (HPV). * **Koilocytes:** The hallmark histological finding for HPV infection (cells with perinuclear halos and wrinkled "raisinoid" nuclei). * **HPV Oncogenesis:** Types 16 and 18 are high-risk for cervical and oropharyngeal carcinoma due to E6 (inhibits p53) and E7 (inhibits Rb) proteins. * **Syphilis Diagnosis:** Condyloma latum is best diagnosed via Dark-field microscopy or serology (RPR/VDRL).

Question 438: A 24-year-old male presented with a lesion on his genitalia after multiple sexual encounters. Which human papillomavirus type is the causative agent?

A. HPV 6, 11 (Correct Answer)
B. HPV 16, 18
C. HPV 31, 33
D. HPV 35, 45

Explanation: **Explanation:** The clinical presentation of a genital lesion (typically **Condyloma acuminatum** or anogenital warts) following sexual contact is most commonly caused by **Human Papillomavirus (HPV) types 6 and 11**. These are classified as **"low-risk" HPV types** because they are associated with benign proliferative lesions rather than invasive squamous cell carcinoma. * **Option A (Correct):** HPV 6 and 11 are responsible for over 90% of cases of genital warts and are also the primary cause of recurrent respiratory papillomatosis. * **Option B (Incorrect):** HPV 16 and 18 are **"high-risk"** oncogenic types. They are the leading cause of cervical cancer, oropharyngeal cancer, and other anogenital malignancies (anal, penile, vulvar). They typically cause flat, subclinical lesions rather than overt warts. * **Options C & D (Incorrect):** HPV types 31, 33, 35, and 45 are also categorized as high-risk types. While they contribute to cervical dysplasia and neoplasia, they are less prevalent than types 16 and 18 and do not typically present as common genital warts. **NEET-PG High-Yield Pearls:** * **Koilocytes:** The hallmark histological finding of HPV infection (cells with perinuclear halo and wrinkled "raisinoid" nuclei). * **Oncoproteins:** HPV E6 inhibits the **p53** tumor suppressor protein; HPV E7 inhibits the **pRb** (Retinoblastoma) protein. * **Vaccination:** The Quadrivalent vaccine (Gardasil) covers types 6, 11, 16, and 18, providing protection against both warts and cervical cancer. * **Diagnosis:** Usually clinical; confirmed by acetic acid test (acetowhitening) or biopsy if diagnosis is uncertain.

Question 439: In early Human Immunodeficiency Virus (HIV) infection, if the ELISA test is negative, what is the recommended next step for diagnosis?

A. Test for p24 antibody
B. Test for gp 120 antibody
C. Test for gp 120 antigen
D. Test for p24 antigen (Correct Answer)

Explanation: ### Explanation **Correct Option: D. Test for p24 antigen** The core concept here is the **"Window Period"** in HIV infection. This is the interval between the initial infection and the point where antibodies become detectable by standard screening tests (ELISA). 1. **Why p24 antigen is correct:** During the early acute phase of HIV infection (typically 2–3 weeks post-exposure), there is a burst of viral replication. The **p24 capsid protein** (antigen) appears in the blood before the body produces a measurable antibody response. Therefore, in a patient with a negative ELISA (which primarily detects antibodies) but high clinical suspicion, testing for p24 antigen (or HIV RNA PCR) is the diagnostic choice to bridge the window period. **Analysis of Incorrect Options:** * **A & B (p24 and gp120 antibodies):** These are antibodies. If the initial ELISA (an antibody-based screening test) is negative, it implies the patient has not yet undergone seroconversion. Testing for specific antibodies like anti-p24 or anti-gp120 will also yield negative results during the window period. * **C (gp120 antigen):** While gp120 is a vital envelope glycoprotein for viral attachment, it is not the standard soluble antigen used for early diagnosis in clinical practice. The p24 antigen is more abundant and easier to detect in the serum during early viremia. **High-Yield Clinical Pearls for NEET-PG:** * **Window Period Duration:** With 4th generation ELISA (which detects both p24 antigen and IgM/IgG antibodies), the window period is reduced to approximately **14–15 days**. * **Order of Appearance:** HIV RNA (10-12 days) → p24 Antigen (14-16 days) → Antibodies (3-8 weeks). * **Confirmatory Test:** While p24 is used for early diagnosis, **Western Blot** was historically the gold standard for confirmation (detecting antibodies to p24, gp41, and gp120/160), though current protocols favor the HIV-1/HIV-2 antibody differentiation immunoassay.

Question 440: Which among the following is the only hepatitis virus that can be cultured?

A. Hepatitis A virus (HAV) (Correct Answer)
B. Hepatitis B virus (HBV)
C. Hepatitis D virus (HDV)
D. Hepatitis C virus (HCV)

Explanation: ### Explanation **Correct Option: A. Hepatitis A virus (HAV)** Hepatitis A virus (HAV) is unique among the primary hepatitis viruses because it is the **only one that can be routinely grown in cell culture**. It can be propagated in various human and primate cell lines (e.g., fetal rhesus monkey kidney cells). However, it is important to note that HAV is fastidious; it grows slowly, does not produce a cytopathic effect (CPE) in most primary isolates, and requires adaptation to the culture medium. This property was historically significant for the development of the inactivated HAV vaccine. **Why other options are incorrect:** * **Hepatitis B virus (HBV):** HBV cannot be grown in standard cell cultures. Research relies on transfected cell lines or "humanized" mouse models because the virus requires highly specific hepatocyte differentiation to replicate. * **Hepatitis D virus (HDV):** As a defective virus, HDV requires the presence of HBV (specifically HBsAg) to replicate and assemble. It cannot be cultured independently. * **Hepatitis C virus (HCV):** For decades, HCV could not be cultured. While specific laboratory strains (like JFH-1) can now be grown in specialized Huh7 cell lines for research, it is not considered "culturable" in the traditional diagnostic or general sense compared to HAV. **High-Yield Clinical Pearls for NEET-PG:** * **Family:** HAV belongs to *Picornaviridae* (Genus: *Hepatovirus*). * **Genome:** All hepatitis viruses are RNA viruses except **HBV**, which is a DNA virus. * **Transmission:** HAV and HEV are transmitted via the **fecal-oral route**, while HBV, HCV, and HDV are parenteral. * **Chronicity:** HAV and HEV (except in pregnancy/immunocompromised) do **not** cause chronic infection. * **Fulminant Hepatitis:** HEV has the highest mortality rate in pregnant women (up to 20%).

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Virology — MCQs

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