Virology Practice Questions

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).

Q: Infection with which of the following agents is particularly dangerous for anemic patients?

Parvovirus. **Explanation:** **1. Why Parvovirus B19 is the Correct Answer:** Parvovirus B19 is uniquely dangerous for anemic patients because it has a specific tropism for **erythroid progenitor cells**. The virus enters these cells via the **P-antigen** (globoside) receptor and replicates within them, leading to direct cytotoxicity and the temporary cessation of erythropoiesis. In healthy individuals, this brief pause in red blood cell (RBC) production is clinically silent. However, in patients with high RBC turnover (e.g., **Sickle Cell Anemia, Hereditary Spherocytosis, Thalassemia**), the bone marrow cannot compensate for the loss. This results in a life-threatening **Aplastic Crisis**, characterized by a sudden drop in hemoglobin and a dangerously low reticulocyte count. **2. Why Other Options are Incorrect:** * **Adenovirus:** Primarily causes respiratory infections, conjunctivitis (pink eye), and hemorrhagic cystitis. It does not target erythroid precursors. * **Cytomegalovirus (CMV):** A member of the Herpesviridae family, it typically causes infectious mononucleosis-like symptoms or severe systemic disease in immunocompromised hosts (retinitis, colitis), but not selective bone marrow suppression of RBCs. * **Herpes Simplex Virus (HSV):** Primarily associated with mucocutaneous lesions (cold sores, genital herpes) and encephalitis; it does not impact erythropoiesis. **3. NEET-PG High-Yield Clinical Pearls:** * **Erythema Infectiosum (Fifth Disease):** Classic presentation in children featuring a "slapped-cheek" rash. * **Hydrops Fetalis:** If a pregnant woman is infected, the virus can cross the placenta, causing severe fetal anemia, high-output cardiac failure, and fetal death. * **Diagnosis:** Look for **"Giant Pronormoblasts"** in the bone marrow and a **low reticulocyte count** (distinguishes aplastic crisis from hemolytic crisis). * **Receptor:** P-antigen (individuals lacking P-antigen are resistant to Parvovirus B19).

Question 1

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 2

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 3

Human Papillomavirus (HPV) initially infects which cells?

Accepted Answer

Basal cells

Answer

Superficial epidermal cells

Answer

Subcutaneous cells

Answer

Dermal cells

Question 4

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 5

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 6

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 7

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.

Question 8

Infection with which of the following agents is particularly dangerous for anemic patients?

Accepted Answer

Parvovirus

Answer

Adenovirus

Answer

Cytomegalovirus

Answer

Herpes simplex virus

Question 9

A 27-year-old man develops malaise, fatigue, and loss of appetite three weeks after a meal. He notes passing dark urine. On physical examination, he has mild scleral icterus and right upper quadrant tenderness. Laboratory studies show serum AST of 62 U/L and ALT of 58 U/L. The total bilirubin concentration is 3.9 mg/dL, and the direct bilirubin concentration is 2.8 mg/dL. His symptoms abate over the next 3 weeks. The cause of his illness is most likely related to contaminated food. Which of the following serologic test results is most likely to be positive in this patient?

Accepted Answer

Anti-HAV

Answer

Anti-HBc

Answer

Anti-HBs

Answer

Anti-HCV

Question 10

Hantavirus is an emerging pathogen that is best described by which of the following statements?

Accepted Answer

Influenza-like symptoms are followed rapidly by acute respiratory failure

Answer

Hemolysis is common in infected patients

Answer

It is acquired by inhalation of aerosols of the urine and feces of infected rodents

Answer

Transmission from human to human is common

Virology — MCQs

Virology — MCQs

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