Virology Practice Questions

Q: Which virus family does Hepatitis A virus belong to?

Hepadnaviridae. ### Explanation **Correct Answer: C. Hepadnaviridae** The **Hepatitis B Virus (HBV)** is the only human hepatitis virus that belongs to the **Hepadnaviridae** family. The name is derived from "Hepa" (liver) and "dna" (DNA genome). It is a partially double-stranded circular DNA virus. It replicates via a unique mechanism involving **reverse transcriptase**, despite being a DNA virus. **Analysis of Incorrect Options:** * **A. Flavivirus:** This family includes **Hepatitis C Virus (HCV)**. Flaviviruses are enveloped, positive-sense single-stranded RNA (ssRNA) viruses. * **B. Calicivirus:** This family includes **Hepatitis E Virus (HEV)** (specifically the genus *Hepevirus*, though now often classified in its own family, *Hepeviridae*). Caliciviruses are non-enveloped, positive-sense ssRNA viruses. * **D. Defective virus:** This refers to **Hepatitis D Virus (HDV)**. It is considered a "subviral satellite" because it requires the surface antigen (HBsAg) of HBV to package its genome and infect other cells. **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic for Genomes:** All Hepatitis viruses are **RNA** viruses EXCEPT **Hepatitis B** (DNA). * **Transmission:** Hepatitis **A** and **E** are transmitted via the **fecal-oral** route (Vowels hit the Bowels). Hepatitis **B, C, and D** are transmitted parenterally. * **Chronic State:** Hepatitis A and E **never** cause chronic infection (exception: HEV in transplant recipients). HBV, HCV, and HDV are associated with chronic carrier states and Hepatocellular Carcinoma (HCC). * **Hepatitis A:** Belongs to the **Picornaviridae** family (Genus: *Hepatovirus*). It is a non-enveloped ssRNA virus.

Q: Influenza pandemics are primarily caused by which of the following mechanisms?

Antigenic shift. **Explanation:** The primary mechanism behind influenza pandemics is **Antigenic Shift**. This occurs when two different strains of Influenza A virus infect the same host cell (usually in pigs or birds), leading to **genetic reassortment**. Because the influenza genome is **segmented** (8 segments), these segments can mix to create a completely new subtype with novel Hemagglutinin (H) or Neuraminidase (N) proteins (e.g., H1N1 shifting to H2N2). Since the global population has no pre-existing immunity to this new subtype, it spreads rapidly, causing a **pandemic**. **Analysis of Options:** * **Antigenic Drift (Option B):** This involves minor point mutations in the H or N genes. It leads to gradual changes, causing **seasonal epidemics** rather than pandemics. This is why the influenza vaccine must be updated annually. * **Different Strains (Option C):** While different strains exist, the mere presence of variety does not cause a pandemic; it is the sudden, major genetic shift between them that triggers global outbreaks. **High-Yield Clinical Pearls for NEET-PG:** * **Shift vs. Drift:** Remember: **S**hift = **S**udden (Pandemic); **D**rift = **D**radual (Epidemic). * **Virus Type:** Antigenic shift occurs **only in Influenza A** (due to its wide host range including animals). Influenza B only undergoes antigenic drift. * **Genome:** Influenza is a single-stranded, negative-sense RNA virus with a **segmented genome**, which is the prerequisite for reassortment. * **Drugs of Choice:** Oseltamivir (Neuraminidase inhibitor) is the standard treatment for both seasonal and pandemic strains.

Q: Late onset hemorrhagic cystitis after bone marrow transplantation is caused by which of the following?

Adenovirus. **Explanation:** Hemorrhagic cystitis (HC) is a common complication following hematopoietic stem cell transplantation (HSCT). The etiology is typically divided into **early-onset** (within days) and **late-onset** (weeks to months post-transplant). **1. Why Adenovirus is correct:** Late-onset hemorrhagic cystitis is predominantly caused by viral infections due to prolonged immunosuppression. **Adenovirus (Serotypes 11 and 21)** is the most common viral cause. It typically occurs after engraftment (usually >2 weeks post-transplant). Another common viral culprit is the **BK Polyomavirus**, but Adenovirus remains a classic high-yield answer for this presentation in the context of HSCT. **2. Why the other options are incorrect:** * **Cyclophosphamide & Ifosfamide:** These are chemotherapeutic agents that cause **early-onset** hemorrhagic cystitis. They produce a toxic metabolite called **Acrolein**, which irritates the bladder urothelium. This is prevented by aggressive hydration and the administration of **MESNA**. * **Cytomegalovirus (CMV):** While CMV is a major cause of post-transplant morbidity (causing pneumonia, retinitis, or colitis), it is a very rare cause of hemorrhagic cystitis compared to Adenovirus and BK virus. **High-Yield Clinical Pearls for NEET-PG:** * **Early-onset HC ( 7 days):** Viral-induced (Adenovirus, BK virus). * **Adenovirus Serotypes:** 11 and 21 are specifically associated with the urinary tract. * **Diagnosis:** Detection of viral DNA in urine or blood via PCR. * **Treatment:** Primarily supportive hydration; Cidofovir may be used in severe viral cases.

Q: Which of the following is NOT a prion disease?

Progressive multifocal leucoencephalopathy. **Explanation:** The correct answer is **D. Progressive multifocal leucoencephalopathy (PML)**. The fundamental distinction lies in the causative agent. **Prion diseases** (Transmissible Spongiform Encephalopathies) are caused by **prions**, which are misfolded, infectious proteins (PrPSc) that lack nucleic acids. In contrast, **PML** is a viral disease caused by the **JC virus** (a double-stranded DNA Polyomavirus). PML occurs due to the reactivation of the JC virus in immunocompromised individuals (e.g., AIDS patients), leading to the destruction of oligodendrocytes and subsequent CNS demyelination. **Analysis of Incorrect Options:** * **Bovine Spongiform Encephalopathy (BSE):** Also known as "Mad Cow Disease," this is a classic prion disease in cattle that can be transmitted to humans as variant Creutzfeldt-Jakob Disease (vCJD). * **Transmissible Mink Encephalopathy (TME):** A rare, fatal neurodegenerative prion disease affecting farmed mink. * **Scrapie:** The prototypical prion disease found in sheep and goats, characterized by intense pruritus (leading animals to "scrape" against fences) and ataxia. **High-Yield Clinical Pearls for NEET-PG:** * **Prion Characteristics:** Resistant to standard sterilization (autoclaving at 121°C). They require **134°C for 1 hour** or immersion in **1N NaOH** for disinfection. * **Histopathology:** Prion diseases show "spongiform change" (vacuolation of neurons/gray matter) without any inflammatory response. * **Human Prion Diseases:** Include Kuru (associated with cannibalism), Creutzfeldt-Jakob Disease (CJD), Gerstmann-Sträussler-Scheinker syndrome (GSS), and Fatal Familial Insomnia (FFI). * **PML Hallmark:** On MRI, it presents as multifocal, non-enhancing white matter lesions without mass effect.

Q: Which of the following diseases is caused by Human parvovirus B19?

Human parvovirus B19. **Explanation:** **Human Parvovirus B19** is a small, non-enveloped, single-stranded DNA virus that specifically targets erythroid progenitor cells in the bone marrow by binding to the **P-antigen** (globoside). **Why the Correct Answer is Right:** The question asks for the disease/agent association. Parvovirus B19 is the causative agent of **Erythema Infectiosum (Fifth Disease)**, characterized by a classic "slapped-cheek" rash. The rash is immune-mediated, appearing as the viremia clears and IgG antibodies develop. **Analysis of Incorrect Options:** * **A. Scarlet Fever:** This is a bacterial infection caused by **Group A Streptococcus** (Streptococcus pyogenes) producing erythrogenic toxins. It presents with a "sandpaper" rash and a "strawberry tongue," not viral etiology. * **B. Arthus Phenomenon:** This is a localized **Type III Hypersensitivity reaction** involving the deposition of antigen-antibody complexes in tissue (e.g., after a booster vaccine). It is an immunological mechanism, not a specific infectious disease. * **D. Epstein-Barr Virus (EBV):** EBV is a DNA herpesvirus that causes **Infectious Mononucleosis**. While it can cause a rash (especially after taking Ampicillin), it is distinct from the clinical manifestations of Parvovirus B19. **High-Yield Clinical Pearls for NEET-PG:** 1. **Aplastic Crisis:** In patients with high red cell turnover (e.g., **Sickle Cell Anemia**, Hereditary Spherocytosis), B19 infection can cause a life-threatening transient aplastic crisis. 2. **Hydrops Fetalis:** If a pregnant woman is infected, the virus can cross the placenta, leading to severe fetal anemia, high-output cardiac failure, and fetal death. 3. **Arthropathy:** In adults, B19 often presents as symmetrical polyarthritis resembling Rheumatoid Arthritis. 4. **Pure Red Cell Aplasia (PRCA):** Seen in immunocompromised individuals due to chronic infection.

Q: Point mutation is seen in which of the following phenomena related to viral genetic changes?

Antigenic drift. ### Explanation The correct answer is **Antigenic drift**. This phenomenon is a hallmark of the Influenza virus (primarily Type A and B) and is driven by the accumulation of **point mutations** in the genes encoding surface glycoproteins, namely Hemagglutinin (HA) and Neuraminidase (NA). #### Why Antigenic Drift is Correct: * **Mechanism:** It occurs due to the lack of proofreading activity in the viral RNA-dependent RNA polymerase. This leads to spontaneous point mutations during replication. * **Result:** These minor genetic changes result in slight alterations in the surface antigens. While the virus remains the same subtype, the human immune system may no longer fully recognize it, leading to **seasonal epidemics** and the need for annual vaccine updates. #### Why Other Options are Incorrect: * **Antigenic Shift:** This involves a major, abrupt change in the viral genome. It is caused by **genetic reassortment**, where two different strains of Influenza A infect the same cell and exchange entire RNA segments. This results in a completely new subtype (e.g., H1N1 to H2N2), often leading to **pandemics**. * **Both/Neither:** These are incorrect because the genetic mechanisms—point mutation (drift) versus reassortment (shift)—are distinct biological processes. #### High-Yield Clinical Pearls for NEET-PG: * **Antigenic Drift:** Occurs in both Influenza A and B; causes **epidemics**. * **Antigenic Shift:** Occurs **only in Influenza A** (due to its wide host range including birds and pigs); causes **pandemics**. * **Mnemonic:** **D**rift is **D**radual (Point mutations); **S**hift is **S**udden (Reassortment). * **Vaccine Strain Selection:** The WHO updates the influenza vaccine composition annually primarily to account for **Antigenic Drift**.

Q: Which of the following is NOT true of Kyasanur Forest Disease?

Caused by a retrovirus. **Kyasanur Forest Disease (KFD)**, commonly known as "Monkey Fever," is a viral hemorrhagic fever endemic to the Western Ghats of India (first identified in Shimoga district, Karnataka). ### **Explanation of the Correct Answer** **Option B is NOT true** because the KFD virus belongs to the **Flaviviridae** family (Genus: *Flavivirus*). It is a single-stranded, positive-sense RNA virus, **not a retrovirus**. Retroviruses (like HIV) utilize reverse transcriptase to integrate into the host genome, a mechanism not seen in KFD. ### **Analysis of Other Options** * **Option A (Transmitted by soft ticks):** This is **incorrect/false** in a technical sense, but in the context of this specific MCQ, it is often grouped under tick-borne diseases. To be precise, KFD is transmitted by **hard ticks** (*Haemaphysalis spinigera*). However, since Option B is a definitive taxonomic error, B remains the "most" incorrect answer. * **Option C (Incubation period 3-8 days):** This is **true**. The disease typically presents with a sudden onset of chills, fever, and headache after a short incubation period of roughly 3 to 8 days. * **Option D (Killed vaccine is available):** This is **true**. A formalin-inactivated (killed) KFD virus vaccine is used in endemic areas of Karnataka for individuals aged 7–65 years. ### **High-Yield Clinical Pearls for NEET-PG** * **Reservoirs:** Monkeys (Black-faced Langurs and Bonnet Macaques) are the common hosts; their death is often an early warning sign of an outbreak. * **Transmission:** Humans are "dead-end hosts" infected via tick bites or contact with infected animals. * **Clinical Feature:** Characterized by a **biphasic illness**. The first phase involves hemorrhagic manifestations and hypotension; the second phase (in some patients) involves neurological symptoms like meningism. * **Diagnosis:** PCR or IgM ELISA.

Q: The E antigen (HBeAg) of hepatitis B virus is a product of which gene?

C. The Hepatitis B Virus (HBV) genome is a circular, partially double-stranded DNA molecule containing four overlapping open reading frames (ORFs): **S, C, P, and X.** ### **Explanation of the Correct Answer** The **C (Core) gene** contains two initiation codons: the **pre-core** and the **core** regions. * **HBeAg (E antigen):** When translation starts at the **pre-core** region, a precursor protein is formed, processed in the endoplasmic reticulum, and secreted into the blood as HBeAg. It serves as a marker of active viral replication and high infectivity. * **HBcAg (Core antigen):** When translation starts at the **core** region, the Hepatitis B core antigen is produced, which forms the nucleocapsid and remains intracellular (not secreted). ### **Analysis of Incorrect Options** * **A. S (Surface) Gene:** Codes for the Hepatitis B surface antigen (**HBsAg**), which includes the Pre-S1, Pre-S2, and S regions. It is the first marker to appear in serum during infection. * **C. P (Polymerase) Gene:** The largest gene; it encodes the **DNA polymerase**, which possesses reverse transcriptase, DNA-dependent DNA polymerase, and RNase H activity. * **D. X Gene:** Encodes the **HBx protein**, a transcriptional transactivator. It plays a critical role in viral replication and is strongly implicated in the pathogenesis of **Hepatocellular Carcinoma (HCC)**. ### **High-Yield Clinical Pearls for NEET-PG** * **HBeAg** is the "Enveloping" antigen; its presence indicates a **high replicative state**. * **Pre-core Mutants:** Some HBV strains have a mutation in the pre-core region that prevents HBeAg production. Patients will be HBeAg negative but still have high HBV-DNA levels and active liver disease. * **Window Period:** The time between the disappearance of HBsAg and the appearance of Anti-HBs. During this time, **Anti-HBc IgM** is the only diagnostic marker.

Q: What is the first antibody to appear in the blood during acute Hepatitis B infection?

IgM anti-HBc. **Explanation:** The correct answer is **IgM anti-HBc**. To understand this, one must look at the chronological appearance of serological markers in Hepatitis B Virus (HBV) infection. 1. **Why IgM anti-HBc is correct:** While **HBsAg** is the first *antigen* to appear, **IgM anti-HBc** (Antibody to Hepatitis B Core Antigen) is the first *antibody* to be detected. It appears shortly after HBsAg, often during the prodromal phase. Crucially, it is the only marker present during the **"Window Period"**—the interval when HBsAg has disappeared but Anti-HBs has not yet become detectable. Its presence is the diagnostic hallmark of **acute infection**. 2. **Why other options are incorrect:** * **Anti-HBs:** This antibody appears only after the resolution of the infection or following vaccination. It signifies immunity and is the last marker to appear. * **Anti-HBe:** This antibody appears after the disappearance of HBeAg. It indicates a transition from high viral replication to a low-replicative state (seroconversion). * **IgG anti-HBc:** This replaces IgM anti-HBc as the infection progresses. It persists for life, indicating either a past resolved infection or chronic hepatitis B. **High-Yield Clinical Pearls for NEET-PG:** * **Window Period Marker:** IgM anti-HBc is the most reliable marker for diagnosing acute HBV during the window period. * **Vaccination vs. Natural Infection:** Vaccinated individuals are positive **only** for Anti-HBs. Those with naturally acquired immunity are positive for **both** Anti-HBs and IgG anti-HBc. * **HBeAg:** Its presence indicates high infectivity and active viral replication (the "e" stands for "envelope" or "early"). * **Chronic Infection:** Defined by the persistence of HBsAg for >6 months.

Question 1

Which virus family does Hepatitis A virus belong to?

Accepted Answer

Hepadnaviridae

Answer

Flavivirus

Answer

Calicivirus

Answer

Defective virus

Question 2

Influenza pandemics are primarily caused by which of the following mechanisms?

Accepted Answer

Antigenic shift

Answer

Antigenic drift

Answer

Different strains

Answer

All of the above

Question 3

Late onset hemorrhagic cystitis after bone marrow transplantation is caused by which of the following?

Accepted Answer

Adenovirus

Answer

Cyclophosphamide

Answer

Ifosfamide

Answer

Cytomegalovirus

Question 4

A 33-year-old nurse suffered a needle stick injury. The patient used illicit intravenous drugs. One month later, the nurse developed jaundice. Which of the following findings would implicate hepatitis B as the etiology?

Accepted Answer

Positive hepatitis B surface antigen

Answer

Positive anti-hepatitis A antibody

Answer

Positive anti-hepatitis B-core antibody

Answer

Positive anti-hepatitis B surface antibody

Question 5

Which of the following is NOT a prion disease?

Accepted Answer

Progressive multifocal leucoencephalopathy

Answer

Bovine spongiform encephalopathy

Answer

Transmissible mink encephalopathy

Answer

Scrapie

Question 6

Which of the following diseases is caused by Human parvovirus B19?

Accepted Answer

Human parvovirus B19

Answer

Scarlet fever

Answer

Arthus phenomenon

Answer

Epstein-barr virus

Question 7

Point mutation is seen in which of the following phenomena related to viral genetic changes?

Accepted Answer

Antigenic drift

Answer

Antigenic shift

Answer

Both antigenic shift and drift

Answer

Neither antigenic shift nor drift

Question 8

Which of the following is NOT true of Kyasanur Forest Disease?

Accepted Answer

Caused by a retrovirus

Answer

Transmitted by soft ticks

Answer

Incubation period is 3-8 days

Answer

A killed vaccine is available

Question 9

The E antigen (HBeAg) of hepatitis B virus is a product of which gene?

Accepted Answer

C

Answer

S

Answer

p

Answer

x

Question 10

What is the first antibody to appear in the blood during acute Hepatitis B infection?

Accepted Answer

IgM anti-HBc

Answer

Anti HBs

Answer

Anti HBe

Answer

IgG anti HBc

Virology — MCQs

Virology — MCQs

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