Virology Practice Questions

Q: Negri bodies are characteristic inclusions found in neurons infected with the rabies virus. In which part of the central nervous system are they most commonly found?

Hippocampus. **Explanation:** **Negri bodies** are pathognomonic intracytoplasmic, eosinophilic inclusion bodies found in neurons infected by the **Rabies virus** (a Lyssavirus of the Rhabdoviridae family). These bodies represent sites of viral replication and consist of viral nucleocapsid proteins. 1. **Why Hippocampus is correct:** While the rabies virus spreads throughout the entire central nervous system (CNS), Negri bodies have a predilection for specific areas. They are most consistently and abundantly found in the **Pyramidal cells of the Hippocampus (Ammon’s horn)** and the **Purkinje cells of the Cerebellum**. Identification of these inclusions in these specific sites remains the gold standard for post-mortem histological diagnosis. 2. **Analysis of Incorrect Options:** * **Brain stem & Spinal cord:** Although the virus travels through the spinal cord and involves the brain stem (leading to cranial nerve dysfunction), Negri bodies are less frequently visualized here compared to the hippocampus. * **Cerebral cortex:** While cortical neurons can contain inclusions, they are not the "most common" or characteristic site used for diagnostic identification. **High-Yield Clinical Pearls for NEET-PG:** * **Morphology:** Negri bodies are sharply outlined, round or oval, and typically measure 1–7 µm. They are **intracytoplasmic** (unlike Herpes, which is intranuclear). * **Staining:** Best visualized using **Sellers’ stain** (basic fuchsin and methylene blue). * **Diagnosis:** The most sensitive and preferred diagnostic test for rabies in animals/humans is the **Direct Fluorescent Antibody (DFA)** test on brain tissue or skin biopsy (from the nape of the neck). * **Clinical Course:** Rabies is characterized by a long incubation period (1–3 months) because of slow retrograde axonal transport (8–20 mm/day) to the CNS.

Q: An immunocompromised person with a history of seizures had an MRI that revealed a temporal lobe lesion. Brain biopsy results showed multinucleated giant cells with intranuclear inclusions. What is the most probable cause of the lesion?

Cytomegalovirus infection. **Explanation:** The correct answer is **Cytomegalovirus (CMV) infection**. In immunocompromised patients (such as those with HIV/AIDS), CMV can cause encephalitis characterized by subacute dementia or focal neurological deficits. The histopathological hallmark of CMV is the presence of **multinucleated giant cells** and large, eosinophilic **intranuclear inclusions** (classically described as "Owl’s eye" appearance). While CMV typically causes periventricular calcifications in neonates, in adults, it can present with focal lesions in various brain regions, including the temporal lobe. **Why other options are incorrect:** * **Toxoplasmosis:** While common in immunocompromised patients, it typically presents as multiple ring-enhancing lesions on MRI. Histology shows tachyzoites and bradyzoites, not intranuclear inclusions. * **Herpes Simplex Encephalitis (HSE):** HSE is the most common cause of sporadic fatal encephalitis and classically involves the temporal lobe. However, it typically affects immunocompetent individuals and is characterized by Cowdry Type A inclusions. The presence of multinucleated giant cells in an immunocompromised setting more strongly points toward CMV or HIV-related pathology. * **Progressive Multifocal Leukoencephalopathy (PML):** Caused by the JC virus, it affects the white matter (demyelination). Histology shows enlarged oligodendrocytes with "ground-glass" nuclei, but not multinucleated giant cells. **NEET-PG High-Yield Pearls:** * **CMV:** "Owl’s eye" inclusions (Intranuclear + Intracytoplasmic). * **HSV:** Cowdry Type A inclusions (Intranuclear only). * **Rabies:** Negri bodies (Intracytoplasmic only). * **PML:** JC Virus; affects subcortical white matter; non-enhancing lesions. * **Temporal Lobe Involvement:** Always consider HSV-1 first in immunocompetent patients, but look for specific histopathological clues for CMV in the immunocompromised.

Q: The common cold is caused primarily by:

Viruses. **Explanation:** The common cold, or acute viral rhinosinusitis, is a self-limiting upper respiratory tract infection (URTI). **1. Why Viruses are Correct:** The vast majority (over 95%) of common colds are caused by viruses. The **Rhinovirus** (a Picornavirus) is the most frequent causative agent, accounting for 30–50% of cases. Other significant viral causes include Coronaviruses, Adenoviruses, Respiratory Syncytial Virus (RSV), and Parainfluenza viruses. These viruses infect the nasal epithelium, leading to inflammation, mucus hypersecretion, and the classic symptoms of rhinorrhea, sneezing, and sore throat. **2. Why Other Options are Incorrect:** * **Bacteria:** While bacteria like *Streptococcus pneumoniae* or *Haemophilus influenzae* can cause secondary infections (e.g., sinusitis or otitis media), they are not the primary cause of the common cold. Antibiotics are therefore ineffective for initial treatment. * **Fungi:** Fungal infections of the respiratory tract (like Aspergillosis or Mucormycosis) are rare and typically occur in immunocompromised individuals; they do not present as a standard "common cold." * **Allergy:** Allergic rhinitis can mimic cold symptoms (sneezing, watery eyes), but it is an IgE-mediated hypersensitivity reaction to environmental triggers (pollen, dust) rather than an infectious process. **NEET-PG High-Yield Pearls:** * **Most common cause:** Rhinovirus (binds to **ICAM-1** receptors). * **Seasonality:** Rhinoviruses peak in autumn/spring; Coronaviruses peak in winter. * **Adenovirus:** Often associated with "Pharyngoconjunctival fever" (sore throat + conjunctivitis). * **Treatment:** Purely symptomatic (decongestants, NSAIDs). Zinc gluconate may reduce duration if started within 24 hours.

Q: Australia antigen is a marker for Hepatitis B infection. Which component of the Hepatitis B virus (HBV) does the Australia antigen represent?

Surface antigen (HBsAg). **Explanation:** The **Australia antigen** is the historical name for the **Hepatitis B surface antigen (HBsAg)**. It was discovered in 1965 by Baruch Blumberg in the serum of an Australian Aboriginal person while studying protein polymorphisms. This discovery was pivotal as it led to the identification of the Hepatitis B virus (HBV). **Why Option A is correct:** HBsAg is the envelope protein of HBV. It is the first serological marker to appear in the blood after infection (usually 2–6 weeks before symptoms) and its persistence beyond 6 months indicates chronic infection. Because it was first identified in an Australian native, it was named the Australia antigen. **Why the other options are incorrect:** * **B. E antigen (HBeAg):** This is a soluble protein representing active viral replication and high infectivity. It is not the Australia antigen. * **C. Core antigen (HBcAg):** This is the nucleocapsid protein. Unlike HBsAg, it is not secreted into the blood and can only be demonstrated in hepatocytes via biopsy. * **D. DNA polymerase:** This is the enzyme responsible for viral replication (reverse transcriptase activity) located within the core, not the surface marker. **High-Yield Clinical Pearls for NEET-PG:** * **Screening Marker:** HBsAg is the primary marker used for screening blood donors and diagnosing acute/chronic HBV. * **Vaccine Component:** Recombinant HBsAg is the component used in the Hepatitis B vaccine. * **Window Period:** The time interval when HBsAg disappears but Anti-HBs has not yet appeared. During this phase, **Anti-HBc IgM** is the only diagnostic marker. * **Dane Particle:** The complete infectious virion (42 nm) consists of the HBsAg envelope surrounding the inner core.

Q: Human Papillomavirus (HPV) initially infects which cells?

Basal cells. **Explanation:** **1. Why Basal Cells are Correct:** Human Papillomavirus (HPV) is a double-stranded DNA virus that specifically targets the **basal layer of the stratified squamous epithelium**. The virus gains entry through micro-abrasions or trauma in the skin or mucosa. It must reach the basal cells because these are the **proliferating (mitotically active) cells** of the epidermis. HPV utilizes the host cell's replication machinery to maintain its genome; as these basal cells divide and differentiate into upper layers, the virus undergoes its full life cycle, eventually shedding from the surface. **2. Why Other Options are Incorrect:** * **Superficial epidermal cells (Stratum Corneum/Granulosum):** While viral replication and assembly occur in these upper layers (koilocytosis is seen here), the *initial* infection must occur at the basal layer to establish a persistent infection. * **Dermal and Subcutaneous cells:** HPV is strictly **epitheliotropic**. It does not infect the dermis or subcutaneous fat because it lacks the necessary receptors to enter these non-epithelial cells and cannot replicate within them. **3. High-Yield Clinical Pearls for NEET-PG:** * **Koilocytes:** The pathognomonic histological feature of HPV infection, characterized by perinuclear halo and pyknotic nuclei, found in the **stratum spinosum and granulosum**. * **HPV Proteins:** **E6** (inhibits p53) and **E7** (inhibits Retinoblastoma/Rb protein) are the primary oncogenic proteins in high-risk types (HPV 16, 18). * **Common Associations:** HPV 6, 11 (Anogenital warts/Condyloma acuminata); HPV 1, 2 (Common warts/Verruca vulgaris). * **Vaccine:** The Gardasil-9 vaccine targets the L1 capsid protein.

Q: A 3-year-old female child presented with low-grade fever, poor feeding, and a rash described as a 'slapped cheek' rash. Which of the following is the predominant site of action of the causative organism?

Bone marrow. **Explanation:** The clinical presentation of a low-grade fever followed by a characteristic **'slapped cheek' rash** (erythema infectiosum or Fifth disease) is diagnostic of **Parvovirus B19** infection. **Why Bone Marrow is correct:** Parvovirus B19 has a specific tropism for **erythroid progenitor cells** (specifically proerythroblasts) in the **bone marrow**. The virus enters these cells by binding to the **P-antigen** (globoside) on the cell surface. Once inside, it replicates and causes cell lysis, leading to a temporary cessation of erythropoiesis. In healthy children, this is clinically insignificant, but in patients with high red cell turnover (e.g., Sickle Cell Anemia, Hereditary Spherocytosis), it can trigger a life-threatening **Aplastic Crisis**. **Why other options are incorrect:** * **Spleen:** While the spleen clears damaged RBCs, it is not the primary site of Parvovirus replication. * **Liver:** The liver is a site of extramedullary hematopoiesis in fetuses (where Parvovirus can cause *Hydrops Fetalis*), but in a 3-year-old, the bone marrow is the definitive site. * **Nerves:** Neurotropism is characteristic of viruses like Poliovirus, Rabies, or VZV, but not Parvovirus B19. **High-Yield Clinical Pearls for NEET-PG:** * **Biphasic Illness:** Initial viremic phase (fever, malaise) followed by an immune-mediated phase (rash and arthralgia). * **Infectivity:** The child is **no longer infectious** once the rash appears. * **Pregnancy:** Infection during pregnancy can lead to **Hydrops Fetalis** due to severe fetal anemia and high-output cardiac failure. * **Diagnosis:** IgM antibodies (acute) or PCR (especially in immunocompromised/aplastic crisis).

Q: Which of the following are arboviral diseases?

Japanese encephalitis, Dengue, Yellow fever. **Explanation** **1. Understanding the Concept (Why B is correct):** Arboviruses (Arthropod-borne viruses) are a functional group of viruses transmitted to humans through the bites of infected arthropods, primarily mosquitoes and ticks. * **Japanese Encephalitis (JE):** Transmitted by the *Culex tritaeniorhynchus* mosquito. It is the leading cause of viral encephalitis in Asia. * **Dengue:** Transmitted by the *Aedes aegypti* mosquito. It is a member of the Flaviviridae family. * **Yellow Fever:** Also transmitted by the *Aedes aegypti* mosquito. It is characterized by jaundice and hemorrhagic manifestations. Since all three diseases listed in Option B are transmitted via arthropod vectors, it is the most comprehensive and correct choice. **2. Analysis of Incorrect Options:** * **Options A, C, and D:** While the diseases listed in these options are indeed arboviral, they are **incomplete**. In NEET-PG, when multiple options contain correct facts, the "most complete" answer is the correct one. Option B encompasses all the major arboviruses mentioned across the other choices. **3. High-Yield Clinical Pearls for NEET-PG:** * **Flaviviridae Family:** All three (JE, Dengue, Yellow Fever) belong to the *Flaviviridae* family and contain ssRNA. * **Vector Specificity:** Remember "C" for *Culex* and "C" for Rice fields (JE); "A" for *Aedes* and "A" for Urban areas (Dengue/Yellow Fever). * **KFD (Kyasanur Forest Disease):** A high-yield Indian arbovirus transmitted by **ticks** (*Haemaphysalis spinigera*). * **Non-Arboviruses:** Note that diseases like Malaria and Kala-azar are arthropod-borne but are **protozoal**, not viral. Similarly, Rabies is viral but **not** arboviral (transmitted via animal bites).

Question 1

Negri bodies are characteristic inclusions found in neurons infected with the rabies virus. In which part of the central nervous system are they most commonly found?

Accepted Answer

Hippocampus

Answer

Brain stem

Answer

Cerebral cortex neurons

Answer

Spinal cord

Question 2

An immunocompromised person with a history of seizures had an MRI that revealed a temporal lobe lesion. Brain biopsy results showed multinucleated giant cells with intranuclear inclusions. What is the most probable cause of the lesion?

Accepted Answer

Cytomegalovirus infection

Answer

Toxoplasmosis

Answer

Herpes simplex encephalitis

Answer

Progressive multifocal leukoencephalopathy

Question 3

The common cold is caused primarily by:

Accepted Answer

Viruses

Answer

Bacteria

Answer

Fungi

Answer

Allergy

Question 4

All are true about H1N1 influenza except?

Accepted Answer

Zanamivir is commonly given through the IV route.

Answer

Fatality is more common in some high-risk groups.

Answer

PCR is used for investigation.

Answer

The WHO latest trivalent influenza vaccine contains two influenza A subtypes (H3N2 and H1N1) and one influenza B component.

Question 5

Australia antigen is a marker for Hepatitis B infection. Which component of the Hepatitis B virus (HBV) does the Australia antigen represent?

Accepted Answer

Surface antigen (HBsAg)

Answer

E antigen (HBeAg)

Answer

Core antigen (HBcAg)

Answer

DNA polymerase

Question 6

Human Papillomavirus (HPV) initially infects which cells?

Accepted Answer

Basal cells

Answer

Superficial epidermal cells

Answer

Subcutaneous cells

Answer

Dermal cells

Question 7

Which of the following statements is NOT true about viral envelopes?

Accepted Answer

The envelope is essential for viral propagation in the next generation.

Answer

The lipid bilayer is derived from host cell membranes.

Answer

The viral proteins embedded within the envelope are encoded by the virus itself.

Answer

The envelope is susceptible to dissolution by organic solvents like ether.

Question 8

A 3-year-old female child presented with low-grade fever, poor feeding, and a rash described as a 'slapped cheek' rash. Which of the following is the predominant site of action of the causative organism?

Accepted Answer

Bone marrow

Answer

Spleen

Answer

Liver

Answer

Nerves

Question 9

Which of the following are arboviral diseases?

Accepted Answer

Japanese encephalitis, Dengue, Yellow fever

Answer

Japanese encephalitis, Dengue

Answer

Japanese encephalitis, Yellow fever

Answer

Dengue, Yellow fever

Question 10

All of the following are true regarding influenza, except?

Accepted Answer

Amantadine is active against influenza B only.

Answer

Point mutations in the hemagglutinin gene cause antigenic drift.

Answer

Acquisition of a completely new hemagglutinin gene causes antigenic shift.

Answer

Amantadine shortens the illness.

Virology — MCQs

Virology — MCQs

On this page

Practice by Chapter

Want unlimited practice?