Virology Practice Questions

Q: Which serological marker best diagnoses a recent Hepatitis B infection?

IgM anti-Hepatitis B core antibody. ### Explanation **Correct Option: D. IgM anti-Hepatitis B core antibody (IgM anti-HBc)** **Why it is correct:** IgM anti-HBc is the hallmark of **acute or recent** Hepatitis B infection (typically within the first 6 months). Its clinical significance is paramount during the **"Window Period"**—the interval where HBsAg has disappeared but Anti-HBs has not yet appeared. During this gap, IgM anti-HBc may be the **only** detectable serological marker of a recent infection. **Analysis of Incorrect Options:** * **A. HBsAg:** While it is the first marker to appear and indicates active infection, it does not distinguish between acute and chronic states. It can remain positive for decades in chronic carriers. * **B. IgG anti-HBe:** This antibody indicates reduced viral replication and low infectivity. It appears later in the course of infection and is not a primary tool for diagnosing a *recent* acute event. * **C. Anti-HBs:** This antibody signifies **immunity**, either through recovery from a natural infection or via vaccination. It appears only after the infection has resolved. **NEET-PG High-Yield Pearls:** 1. **Window Period Marker:** IgM anti-HBc is the diagnostic marker of choice when HBsAg and Anti-HBs are both negative. 2. **Vaccination vs. Natural Infection:** * **Vaccinated:** Only Anti-HBs is positive. * **Prior Natural Infection:** Both Anti-HBs and IgG anti-HBc are positive. 3. **Chronic Infection:** Defined by the persistence of HBsAg for >6 months. 4. **HBeAg:** Indicates high viral load and high infectivity ("e" for envelope/excess replication).

Q: Which virus is implicated in Burkitt's lymphoma?

EBV. **Explanation:** **Epstein-Barr Virus (EBV)**, also known as Human Herpesvirus 4 (HHV-4), is the primary etiological agent implicated in **Burkitt’s Lymphoma**. The virus infects B-lymphocytes via the **CD21 receptor**. The oncogenic mechanism involves a characteristic chromosomal translocation, most commonly **t(8;14)**, which leads to the overexpression of the **c-myc proto-oncogene**, resulting in uncontrolled B-cell proliferation. **Analysis of Options:** * **A. EBV (Correct):** Strongly associated with the endemic (African) form of Burkitt’s lymphoma (found in 100% of cases) and to a lesser extent with sporadic and HIV-associated forms. * **B. HTLV (Human T-cell Lymphotropic Virus):** Specifically associated with **Adult T-cell Leukemia/Lymphoma (ATLL)**, not B-cell lymphomas. * **C. HPV (Human Papillomavirus):** Implicated in squamous cell carcinomas, primarily **Cervical Cancer** (Types 16, 18) and oropharyngeal cancers. * **D. HHV8 (KSHV):** Associated with **Kaposi Sarcoma** and Primary Effusion Lymphoma, typically in immunocompromised patients. **High-Yield Clinical Pearls for NEET-PG:** * **Histology:** Burkitt’s lymphoma classically shows a **"Starry Sky" appearance** (tingible body macrophages against a background of dark neoplastic B-cells). * **Other EBV Associations:** Infectious Mononucleosis (Heterophile positive), Nasopharyngeal Carcinoma, Oral Hairy Leukoplakia (in HIV), and Hodgkin’s Lymphoma (Mixed cellularity type). * **Diagnosis:** EBV is detected via the Monospot test (Paul-Bunnell test) or by identifying EBNA (EBV Nuclear Antigen).

Q: The Dane particle is the?

HBV. **Explanation:** The **Dane particle** is the complete, infectious virion of the **Hepatitis B Virus (HBV)**. First identified by DS Dane in 1970 via electron microscopy, it is a spherical structure measuring approximately **42 nm** in diameter. It consists of an inner nucleocapsid core (containing HBcAg, the DNA genome, and DNA polymerase) surrounded by an outer lipoprotein envelope containing the surface antigen (HBsAg). **Analysis of Options:** * **Option A (HBV):** Correct. The 42 nm Dane particle represents the intact, double-shelled virus capable of replication. It is found in the serum along with smaller (22 nm) spherical and tubular forms, which are non-infectious surpluses of HBsAg. * **Option B (IgG anti-HAV):** Incorrect. This is a host antibody indicating past infection or immunity to Hepatitis A; it is not a viral particle. * **Option C (Delta Virus):** Incorrect. This refers to Hepatitis D (HDV), a defective RNA virus that requires the HBsAg coat from HBV to replicate but is not called the Dane particle. * **Option D (HBcAg):** Incorrect. This is the Hepatitis B core antigen, which is a component *inside* the Dane particle, not the particle itself. **High-Yield NEET-PG Pearls:** * **Genome:** HBV is the only DNA virus among the Hepatitis viruses (partially double-stranded circular DNA). * **Morphology:** Under EM, HBV shows three forms: Dane particles (infectious), spherical forms, and filamentous forms (both non-infectious HBsAg). * **Serology:** HBsAg is the first marker to appear in blood; Anti-HBs indicates immunity. * **DNA Polymerase:** HBV possesses reverse transcriptase activity during its replication cycle.

Q: Which viruses commonly cause gastroenteritis?

All of the above. Viral gastroenteritis is a leading cause of severe diarrhea and dehydration worldwide. The correct answer is **D (All of the above)** because Rotavirus, Norwalk virus (Norovirus), and specific serotypes of Adenovirus are the primary etiologic agents of viral diarrhea. ### **Detailed Explanation:** 1. **Rotavirus (Option A):** A Reovirus (dsRNA, segmented) that is the **most common cause of severe diarrhea in infants and young children** worldwide. It primarily affects the duodenum and jejunum, leading to malabsorption and osmotic diarrhea. 2. **Norwalk virus / Norovirus (Option B):** A Calicivirus (ssRNA) known as the **most common cause of gastroenteritis outbreaks** across all age groups. It is frequently associated with "cruise ship diarrhea," schools, and nursing homes due to its low infectious dose and environmental stability. 3. **Adenovirus (Option C):** While most Adenoviruses cause respiratory infections, **Serotypes 40 and 41** (Enteric Adenoviruses) are significant causes of infantile gastroenteritis. Unlike others, these are non-enveloped DNA viruses. ### **High-Yield Clinical Pearls for NEET-PG:** * **Rotavirus:** Characterized by a "wheel-like" appearance on electron microscopy. The **NSP4 enterotoxin** is responsible for inducing secretory diarrhea. * **Norovirus:** Currently the leading cause of viral gastroenteritis globally since the introduction of the Rotavirus vaccine. * **Astrovirus:** Another important cause, identified by its "star-shaped" morphology. * **Mechanism:** Most of these viruses cause blunting of the intestinal villi, leading to a decrease in absorptive surface area and transient lactose intolerance.

Q: Break bone fever is caused by which of the following viruses?

Dengue. **Explanation:** **Dengue virus** is the correct answer. It is a single-stranded RNA virus belonging to the **Flaviviridae** family, transmitted primarily by the *Aedes aegypti* mosquito. It is clinically referred to as **"Break-bone fever"** because patients often experience excruciating joint and muscle pain (myalgia and arthralgia) that feels as though their bones are breaking. **Analysis of Incorrect Options:** * **Variola:** This is the causative agent of **Smallpox**. It is a DNA virus (Poxviridae) characterized by a centrifugal rash and umbilicated pustules, not severe bone pain. * **Coxsackie:** A member of the Picornaviridae family. Coxsackie A typically causes **Hand-Foot-and-Mouth Disease** or Herpangina, while Coxsackie B is a common cause of **Myocarditis** and Pleurodynia (Bornholm disease). * **Adenovirus:** A non-enveloped DNA virus primarily associated with **Pharyngoconjunctival fever**, epidemic keratoconjunctivitis, and hemorrhagic cystitis. **High-Yield Clinical Pearls for NEET-PG:** * **Vector:** *Aedes aegypti* (Day biter; breeds in clean stagnant water). * **Serotypes:** There are 4 serotypes (DEN 1-4). Infection with one provides lifelong immunity to that specific serotype but increases the risk of **Dengue Hemorrhagic Fever (DHF)** upon secondary infection with a different serotype due to **Antibody-Dependent Enhancement (ADE)**. * **Diagnosis:** * Day 1–5: **NS1 Antigen** (Best early marker). * After Day 5: **IgM/IgG ELISA**. * **Hallmark Lab Finding:** Thrombocytopenia (low platelet count) and hemoconcentration (increased hematocrit). * **Tourniquet Test:** Used as a bedside screening tool for capillary fragility in DHF.

Q: Which staining method is useful for the antemortem diagnosis of rabies?

Direct fluorescent antibody stain. **Explanation:** The **Direct Fluorescent Antibody (DFA) test** is the gold standard for rabies diagnosis. It detects rabies virus antigens in clinical specimens. For **antemortem diagnosis**, the specimen of choice is a **full-thickness skin biopsy from the nape of the neck** (containing hair follicles and cutaneous nerves). DFA is preferred due to its high sensitivity and specificity, allowing for rapid detection before death. **Analysis of Options:** * **Sellers Stain (Option A):** This is used to visualize **Negri bodies** (intracytoplasmic inclusion bodies). While characteristic of rabies, Negri bodies are only present in about 70-80% of cases and are typically identified in **postmortem** brain tissue (Ammon’s horn). * **Macchiavello Stain (Option B):** This stain is historically used to identify **Rickettsiae** and **Chlamydia** (inclusion bodies), not the rabies virus. * **Giemsa Stain (Option C):** This is a versatile hematological stain used for malaria parasites, *Chlamydia*, and *Borrelia*, but it is not specific or diagnostic for rabies. **High-Yield Clinical Pearls for NEET-PG:** * **Gold Standard:** DFA is the most reliable test for both antemortem (skin biopsy) and postmortem (brain tissue) diagnosis. * **Negri Bodies:** These are pathognomonic for rabies but their absence does *not* rule out the disease. * **Specimen for Antemortem Diagnosis:** Skin biopsy from the nape of the neck, saliva (for RT-PCR), and CSF. * **Prophylaxis:** Rabies is 100% fatal once symptoms appear, making post-exposure prophylaxis (PEP) with wound cleaning, vaccine, and RIG (if indicated) critical.

Q: What is the primary treatment for Herpes zoster?

Ganciclovir. **Explanation:** **Correct Answer: B. Ganciclovir** The primary treatment for infections caused by the Herpesviridae family involves DNA polymerase inhibitors. While **Acyclovir** is typically the first-line treatment for Herpes zoster (Varicella-Zoster Virus), among the options provided, **Ganciclovir** is the only drug belonging to the same class of guanosine analogs. Ganciclovir works by inhibiting viral DNA polymerase, effectively halting viral replication. In clinical practice, while Ganciclovir is more commonly associated with Cytomegalovirus (CMV), it possesses significant activity against VZV and is the most appropriate choice among the listed antivirals. **Analysis of Incorrect Options:** * **A. Zidovudine (AZT):** A Nucleoside Reverse Transcriptase Inhibitor (NRTI) used exclusively in the treatment of HIV/AIDS. It has no efficacy against DNA viruses like VZV. * **C. Ribavirin:** A guanosine analog used primarily for Hepatitis C (in combination with interferon) and Respiratory Syncytial Virus (RSV). It is not indicated for Herpes zoster. * **D. Nevirapine:** A Non-Nucleoside Reverse Transcriptase Inhibitor (NNRTI) used in the management of HIV-1. It does not inhibit DNA polymerase. **NEET-PG High-Yield Pearls:** * **Drug of Choice:** Oral **Acyclovir**, Valacyclovir, or Famciclovir are preferred for Herpes zoster to reduce the duration of viral shedding and the risk of **Post-Herpetic Neuralgia (PHN)**. * **Mechanism:** Acyclovir/Ganciclovir require initial phosphorylation by viral **thymidine kinase** (absent in host cells), ensuring selective toxicity. * **Clinical Sign:** Look for "Dew drops on a rose petal" appearance (vesicles on an erythematous base) following a dermatomal distribution. * **Tzanck Smear:** Characteristically shows **Multinucleated Giant Cells** and Cowdry Type A inclusion bodies.

Question 1

Trans-placental spread is least associated with which of the following pathogens?

Accepted Answer

Herpes Simplex virus

Answer

Hepatitis B virus

Answer

Rubella virus

Answer

Human Immunodeficiency Virus

Question 2

Which serological marker best diagnoses a recent Hepatitis B infection?

Accepted Answer

IgM anti-Hepatitis B core antibody

Answer

Hepatitis B surface antigen (HBsAg)

Answer

IgG anti-Hepatitis B e antibody

Answer

Anti-Hepatitis B surface antibody

Question 3

Sharps, syringes, and needles used for patients whose HIV test results are not known, should be immersed in which of the following solutions for disinfection?

Accepted Answer

1% Povidone-iodine solution

Answer

Boiling water

Answer

1% solution of sodium hypochlorite

Answer

10% solution of Dettol

Question 4

Which virus is implicated in Burkitt's lymphoma?

Accepted Answer

EBV

Answer

HTLV

Answer

HPV

Answer

HHV8

Question 5

The Dane particle is the?

Accepted Answer

HBV

Answer

IgG anti HAV

Answer

Delta Virus

Answer

HBC Ag

Question 6

Which viruses commonly cause gastroenteritis?

Accepted Answer

All of the above

Answer

Rotavirus

Answer

Norwalk virus

Answer

Adenovirus

Question 7

Break bone fever is caused by which of the following viruses?

Accepted Answer

Dengue

Answer

Variola

Answer

Coxsackie

Answer

Adenovirus

Question 8

Which of the following is characteristic only of viruses?

Accepted Answer

They affect the production of interferon and are sensitive to it.

Answer

They are intracellular organisms

Answer

They reproduce by binary fission

Answer

They can be grown on inanimate media

Question 9

Which staining method is useful for the antemortem diagnosis of rabies?

Accepted Answer

Direct fluorescent antibody stain

Answer

Sellers stain

Answer

Macchiavello stain

Answer

Giemsa stain

Question 10

What is the primary treatment for Herpes zoster?

Accepted Answer

Ganciclovir

Answer

Zidovudine

Answer

Ribavirin

Answer

Nevirapine

Virology — MCQs

Virology — MCQs

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