Virology Practice Questions

Q: Which of the following is the least common chronic complication of measles?

Subacute sclerosing panencephalitis. **Explanation:** The question asks for the **least common chronic complication** of measles. While measles is known for its acute symptoms, its complications are what lead to significant morbidity and mortality. **Why Subacute Sclerosing Panencephalitis (SSPE) is the correct answer:** SSPE is a progressive, fatal neurodegenerative disease caused by a persistent infection with a defective measles virus. While it is a severe **chronic** complication, it is extremely rare, occurring in approximately **1 in 10,000 to 1 in 100,000** cases of measles. It typically manifests 7–10 years after the initial infection. Because of its very low incidence compared to acute complications, it is the "least common" among the choices provided. **Analysis of Incorrect Options:** * **Diarrhoea:** This is the **most common** complication of measles overall (occurring in about 8% of cases), particularly in malnourished children. * **Pneumonia:** This is the **most common cause of death** associated with measles in children. It can be caused by the measles virus itself (Hecht’s giant cell pneumonia) or secondary bacterial infections. * **Otitis Media:** This is a very frequent bacterial complication, occurring in nearly 7–10% of cases, often leading to permanent hearing loss if untreated. **NEET-PG High-Yield Pearls:** * **Most common complication:** Diarrhoea. * **Most common cause of death:** Pneumonia. * **SSPE Diagnosis:** Look for high titers of anti-measles antibodies in the CSF and serum, and **periodic complexes** on EEG. * **Vitamin A:** Supplementation reduces the severity and mortality of measles complications. * **Koplik spots:** Pathognomonic sign found on the buccal mucosa opposite the lower second molars during the pre-eruptive stage.

Q: Which Human Papillomavirus (HPV) types are considered high-risk?

16 and 18. **Explanation:** Human Papillomavirus (HPV) is a double-stranded DNA virus with over 200 genotypes. These are clinically categorized based on their oncogenic potential into "High-risk" and "Low-risk" types. **1. Why Option A is Correct:** **HPV 16 and 18** are the most potent **high-risk (oncogenic)** types. They are responsible for approximately 70% of all cervical cancers worldwide. Their oncogenicity is primarily due to the overexpression of two early proteins: * **E6:** Binds to and degrades the **p53** tumor suppressor protein. * **E7:** Binds to and inactivates the **pRb** (Retinoblastoma) protein. This leads to uncontrolled cell cycle progression and genomic instability. **2. Why Other Options are Incorrect:** * **Option B (6 and 11):** These are **low-risk** types. They are the primary cause of **Condyloma acuminatum** (anogenital warts) and Recurrent Respiratory Papillomatosis (RRP). They rarely progress to malignancy. * **Options C & D:** Types 42, 44, 70, and 72 are generally considered low-risk or of undetermined significance and are not the primary drivers of cervical carcinogenesis. **High-Yield Clinical Pearls for NEET-PG:** * **Most common type in Cervical Cancer:** HPV 16 (followed by 18). * **Most common type in Oropharyngeal Cancer:** HPV 16. * **Screening:** The Papanicolaou (Pap) smear looks for **Koilocytes** (cells with perinuclear halo and wrinkled "raisinoid" nuclei). * **Vaccination:** The **9-valent vaccine (Gardasil 9)** covers types 6, 11, 16, 18, 31, 33, 45, 52, and 58. * **Schiller’s Test:** Used during colposcopy; cancerous areas are **Lugol’s iodine negative** (remain pale/yellow) due to lack of glycogen.

Q: A patient presents with acute symptoms of hepatitis and tests positive for HDV antigen. Given that HDV requires HBV for replication, which of the following sets of serological markers indicates chronic HBV infection with superinfection by HDV?

HBsAg+, HBeAg+, Anti-HBc IgM-, Anti-HBc IgG+, Anti-HBs-. ### Explanation The key to solving this question lies in distinguishing between **HBV/HDV Co-infection** and **HDV Superinfection**. Hepatitis D Virus (HDV) is a defective RNA virus that requires the Hepatitis B Surface Antigen (HBsAg) coat for its assembly and transmission. **1. Why Option B is Correct:** In **HDV Superinfection**, a patient who is already a chronic carrier of HBV (or has chronic hepatitis B) becomes infected with HDV. * **Chronic HBV status** is defined by the presence of **HBsAg** for >6 months and the presence of **Anti-HBc IgG**. * The absence of **Anti-HBc IgM** is crucial here, as IgM indicates an acute HBV infection. * Therefore, the profile **HBsAg+, Anti-HBc IgG+, and Anti-HBc IgM-** confirms a pre-existing chronic HBV state upon which the acute HDV infection has occurred. **2. Analysis of Incorrect Options:** * **Option A:** This profile (Anti-HBc IgM+) indicates an **acute HBV infection**. If HDV markers were also present, this would represent **Co-infection** (simultaneous infection with both viruses), not superinfection. * **Option C:** This indicates a **resolved HBV infection** (HBsAg negative, Anti-HBs positive, and Anti-HBc IgG positive). HDV cannot replicate without active HBsAg production. * **Option D:** This indicates **immunity via vaccination** (only Anti-HBs positive; Anti-HBc is negative as there was no exposure to the viral core). **3. High-Yield Clinical Pearls for NEET-PG:** * **Co-infection:** Usually results in acute hepatitis that resolves; low risk of chronicity. * **Superinfection:** Often leads to severe "flare-up" of hepatitis and carries a very high risk (up to 80%) of progressing to **chronic HDV**, cirrhosis, and liver failure. * **HDV Diagnosis:** Look for HDV-Ag or HDV-RNA in the blood. * **Prevention:** The HBV vaccine is the most effective way to prevent HDV infection in HBV-naive individuals.

Q: Subacute sclerosing panencephalitis (SSPE) is not diagnosed by which of the following?

Electroencephalogram (EEG). **Explanation:** Subacute Sclerosing Panencephalitis (SSPE) is a progressive, fatal neurodegenerative disease caused by a persistent infection with a mutant strain of the **Measles virus**. The diagnosis relies on demonstrating high titers of measles antibodies and viral presence in the CNS. **Why Option A is the Correct Answer:** While an **Electroencephalogram (EEG)** is a vital supportive tool in the clinical workup of SSPE—characteristically showing **periodic, high-voltage slow-wave complexes** (Radermecker complexes)—it is **not diagnostic** on its own. EEG findings are suggestive but non-specific, as similar patterns can occur in other encephalopathies. Definitive diagnosis requires microbiological or pathological evidence of the virus. **Analysis of Incorrect Options:** * **Option B & C:** A hallmark of SSPE is the presence of **intrathecal synthesis** of measles antibodies. Diagnosis requires demonstrating high titers of anti-measles IgG in both the **blood (serum)** and **CSF**. A CSF-to-serum antibody ratio is often used to confirm the diagnosis. * **Option D:** Demonstration of **Measles virus antigen** or viral RNA in brain tissue via biopsy (or autopsy) using immunohistochemistry or PCR is a definitive diagnostic method. Histology typically shows **Cowdry type A inclusion bodies**. **High-Yield Clinical Pearls for NEET-PG:** * **Latency:** SSPE typically occurs 5–10 years after an initial measles infection. * **Pathogenesis:** Caused by a "defective" measles virus (mutations in the **M (Matrix) protein** prevent normal viral budding). * **CSF Findings:** Raised gamma globulins (oligoclonal bands) but **normal** glucose and cell count. * **Clinical Stages:** Characterized by behavioral changes, followed by **myoclonic jerks**, and eventually dementia/coma.

Q: Which of the following is a true finding regarding Hepatitis C virus?

Antibody to HCV may not be detected in the acute stage. **Explanation:** **Hepatitis C Virus (HCV)**, a member of the *Flaviviridae* family, is characterized by a significant "window period." In the acute stage of infection, anti-HCV antibodies may take **6 to 12 weeks** (or longer) to develop. Therefore, a patient may be viremic and symptomatic while testing negative for antibodies. The definitive diagnosis during this early phase is made by detecting **HCV RNA** using PCR. **Analysis of Options:** * **Option A (Incorrect):** HCV is primarily transmitted via **parenteral routes** (blood transfusions, IV drug use). Hepatitis A and E are the primary viruses spread via the fecal-oral route. * **Option C (Incorrect):** HCV is notorious for its high chronicity rate. Approximately **75%–85%** of infected individuals develop chronic hepatitis, which can lead to cirrhosis and hepatocellular carcinoma (HCC). * **Option D (Incorrect):** While historically difficult to grow, HCV **can be cultured** in vitro using specific cell lines (e.g., Huh7 human hepatoma cells). This was a breakthrough that allowed for the development of Direct-Acting Antivirals (DAAs). **High-Yield Clinical Pearls for NEET-PG:** * **Most common cause** of post-transfusion hepatitis (historically). * **HCV RNA** is the first marker to appear (as early as 1–2 weeks post-exposure). * **Genotype 3** is the most common genotype found in India. * Unlike Hepatitis B, there is **no vaccine** available for HCV due to the high antigenic variation in its E2 envelope glycoprotein (hypervariable regions).

Q: What is true about prions?

Associated with misfolding of protein. **Explanation:** Prions (Proteinaceous Infectious Particles) are unique pathogens that lack nucleic acids (DNA/RNA). The fundamental mechanism of prion disease involves the **misfolding of a normal host protein**, known as PrPc (cellular prion protein), into an abnormal, protease-resistant isoform called **PrPsc** (scrapie prion protein). This misfolded protein acts as a template, inducing other normal proteins to misfold, leading to neurodegeneration. **Analysis of Options:** * **A. Encoded by viral genome:** Incorrect. Prions are not viruses; they are encoded by the host's own **PRNP gene** located on chromosome 20. * **C. Non-infectious:** Incorrect. Prions are highly infectious and can be transmitted via contaminated neurosurgical instruments, corneal transplants, or ingestion of infected tissue (e.g., Kuru). * **D. Immunogenic:** Incorrect. Because prions are derived from host proteins, the immune system does not recognize them as foreign. Therefore, they **do not elicit an inflammatory or immune response** (no fever, no antibody production). **High-Yield Clinical Pearls for NEET-PG:** * **Resistance:** Prions are notoriously resistant to standard sterilization methods (autoclaving, UV light, and formalin). They require specific protocols like **1N NaOH for 1 hour** or gravity displacement autoclaving at **134°C**. * **Histopathology:** Characterized by **spongiform degeneration** (vacuolation of neurons), neuronal loss, and amyloid plaques without inflammation. * **Key Diseases:** Creutzfeldt-Jakob Disease (CJD), Kuru, Fatal Familial Insomnia (FFI) in humans; Bovine Spongiform Encephalopathy (Mad Cow Disease) in cattle. * **Diagnosis:** Detection of **14-3-3 protein** in CSF is a significant diagnostic marker.

Q: Which is the longest DNA segment of the hepatitis B virus genome?

P gene. **Explanation:** The Hepatitis B Virus (HBV) is a unique, partially double-stranded circular DNA virus (Hepadnaviridae). Its compact genome consists of approximately 3,200 nucleotides and contains four overlapping open reading frames (ORFs). **1. Why P gene is correct:** The **P gene** is the largest ORF, encompassing nearly **80% of the entire HBV genome**. It encodes the viral **DNA polymerase**, a multifunctional enzyme that possesses reverse transcriptase, DNA-dependent DNA polymerase, and RNase H activities. It is essential for viral replication and is the primary target for antiviral drugs like Tenofovir and Entecavir. **2. Why other options are incorrect:** * **S gene:** Encodes the surface proteins (HBsAg). While clinically significant for diagnosis, it is much shorter than the P gene. * **C gene:** Encodes the core protein (HBcAg) and the precore protein (HBeAg). It is significantly smaller than the P gene. * **X gene:** This is the **smallest ORF** in the HBV genome. It encodes the HBx protein, which acts as a transcriptional transactivator and is implicated in the development of hepatocellular carcinoma (HCC). **High-Yield Clinical Pearls for NEET-PG:** * **Genome Structure:** HBV has a "relaxed circular DNA" (rcDNA) which is converted into **cccDNA** (covalently closed circular DNA) in the host nucleus—the template for all viral transcripts. * **Replication:** HBV is the only DNA virus that replicates via an **RNA intermediate** using reverse transcriptase. * **Dane Particle:** The complete infectious virion is a 42 nm spherical particle. * **Smallest Gene:** X gene (associated with oncogenesis). * **Largest Gene:** P gene (encodes Polymerase).

Q: All of the following are true about HIV infection except?

Increased release of acid labile interferon. **Explanation:** The correct answer is **C (Increased release of acid-labile interferon)** because HIV infection is actually associated with the production of **acid-labile Interferon-alpha (IFN-α)**, not its increased release as a protective mechanism. In HIV patients, the presence of acid-labile IFN-α is a marker of disease progression and is often found in the serum of those with AIDS or symptomatic HIV, rather than being a standard physiological response to the virus. **Analysis of Options:** * **Option A (Enveloped RNA virus):** This is **true**. HIV is a member of the *Lentivirus* genus within the *Retroviridae* family. It possesses a lipid envelope derived from the host cell membrane and contains two copies of single-stranded positive-sense RNA. * **Option B (Rate of killing vs. T4 molecules):** This is **true**. The HIV gp120 envelope glycoprotein binds specifically to the **CD4 (T4) molecule**. Cells with higher densities of CD4 receptors on their surface are more susceptible to viral entry and subsequent cytopathic destruction. * **Option D (Decreased delayed hypersensitivity):** This is **true**. HIV causes a profound depletion of CD4+ T cells, leading to a defect in cell-mediated immunity. This results in **anergy**, manifested as a decreased or absent delayed-type hypersensitivity (DTH) skin test response (e.g., to Tuberculin). **High-Yield Clinical Pearls for NEET-PG:** * **Primary Receptor:** CD4 molecule. * **Co-receptors:** **CCR5** (macrophages/early infection) and **CXCR4** (T-cells/late infection). Individuals with a homozygous **CCR5-Δ32 mutation** are resistant to HIV-1 infection. * **Hallmark Immunological Defect:** Inversion of the CD4:CD8 ratio (normal is ~2:1; in AIDS it is <1:1). * **Acid-labile IFN-α:** Its presence in HIV is unusual because IFN-α is typically acid-stable; its appearance in HIV/SLE is a specific diagnostic nuance.

Q: Which of the following conditions is caused by HHV-8?

Kaposi sarcoma. **Explanation:** **Human Herpesvirus 8 (HHV-8)**, also known as **Kaposi Sarcoma-associated Herpesvirus (KSHV)**, is a gamma-herpesvirus that primarily infects vascular endothelial cells. It carries oncogenes (like viral cyclin and v-FLIP) that promote cell proliferation and inhibit apoptosis. In immunocompromised states, particularly HIV/AIDS, HHV-8 leads to the development of **Kaposi Sarcoma**, a multicentric vascular tumor characterized by spindle cells and slit-like neovascular spaces. **Analysis of Incorrect Options:** * **A & B (Burkitt's Lymphoma & Nasopharyngeal Carcinoma):** Both are strongly associated with **Epstein-Barr Virus (EBV)**, also known as HHV-4. EBV is a gamma-herpesvirus that infects B-cells and epithelial cells. * **D (Hepatic Carcinoma):** Hepatocellular carcinoma is primarily linked to chronic infections with **Hepatitis B Virus (HBV)** and **Hepatitis C Virus (HCV)**, as well as aflatoxin exposure. **High-Yield Clinical Pearls for NEET-PG:** * **HHV-8 Spectrum:** Besides Kaposi Sarcoma, HHV-8 is also the causative agent of **Primary Effusion Lymphoma (PEL)** and **Multicentric Castleman Disease**. * **Transmission:** HHV-8 is most commonly transmitted through saliva and sexual contact. * **Histopathology:** Look for "spindle-shaped cells" and "extravasated RBCs" in biopsy descriptions of Kaposi Sarcoma. * **Classification:** Remember the "Rule of 8"—HHV-8 causes Kaposi Sarcoma (the 8th virus causes the sarcoma starting with 'K', the 11th letter, but often associated with AIDS/Advanced stages).

Q: Influenza pandemics are primarily caused by which type of influenza virus?

Type A. **Explanation:** **Influenza Type A** is the primary cause of pandemics due to its unique ability to undergo **Antigenic Shift**. This process involves a major genetic recombination (reassortment) between different viral strains, resulting in a completely new subtype with novel Hemagglutinin (H) or Neuraminidase (N) surface antigens. Because the human population has little to no pre-existing immunity to these new subtypes, the virus spreads globally, leading to a pandemic. Type A also has a broad host range, infecting humans, birds, and pigs, which facilitates this genetic mixing. **Why other options are incorrect:** * **Type B:** While it causes significant seasonal epidemics, it does not cause pandemics. This is because Type B undergoes **Antigenic Drift** (minor point mutations) but not Shift, and it lacks an animal reservoir to facilitate reassortment. * **Type C:** This type generally causes only mild respiratory illness or sporadic cases and does not lead to epidemics or pandemics. * **Type D:** Primarily affects cattle and is not known to infect or cause disease in humans. **High-Yield NEET-PG Pearls:** * **Antigenic Shift:** Sudden, major change; causes **Pandemics** (Only Type A). * **Antigenic Drift:** Gradual, minor mutations; causes **Epidemics** (Types A and B). * **Nomenclature:** The most common subtypes currently circulating in humans are H1N1 and H3N2. * **Vaccine:** The influenza vaccine is updated annually to match the predicted circulating strains (usually quadrivalent, covering two Type A and two Type B strains).

Question 1

Which of the following is the least common chronic complication of measles?

Accepted Answer

Subacute sclerosing panencephalitis

Answer

Diarrhoea

Answer

Pneumonia

Answer

Otitis media

Question 2

Which Human Papillomavirus (HPV) types are considered high-risk?

Accepted Answer

16 and 18

Answer

6 and 11

Answer

42 and 44

Answer

70 and 72

Question 3

A patient presents with acute symptoms of hepatitis and tests positive for HDV antigen. Given that HDV requires HBV for replication, which of the following sets of serological markers indicates chronic HBV infection with superinfection by HDV?

Accepted Answer

HBsAg+, HBeAg+, Anti-HBc IgM-, Anti-HBc IgG+, Anti-HBs-

Answer

HBsAg+, HBeAg+, Anti-HBc IgM+, Anti-HBc IgG-, Anti-HBs-

Answer

HBsAg-, HBeAg-, Anti-HBc IgM-, Anti-HBc IgG+, Anti-HBs+

Answer

HBsAg-, HBeAg-, Anti-HBc IgM-, Anti-HBc IgG-, Anti-HBs+

Question 4

Subacute sclerosing panencephalitis (SSPE) is not diagnosed by which of the following?

Accepted Answer

Electroencephalogram (EEG)

Answer

Antibodies to measles in cerebrospinal fluid (CSF)

Answer

Antibodies to measles in blood

Answer

Measles antigen in brain biopsy

Question 5

Which of the following is a true finding regarding Hepatitis C virus?

Accepted Answer

Antibody to HCV may not be detected in the acute stage

Answer

Spreads via the fecal-oral route

Answer

Does not cause chronic hepatitis

Answer

Cannot be cultured in vitro

Question 6

What is true about prions?

Accepted Answer

Associated with misfolding of protein

Answer

Encoded by viral genome

Answer

Non-infectious

Answer

Immunogenic

Question 7

Which is the longest DNA segment of the hepatitis B virus genome?

Accepted Answer

P gene

Answer

X gene

Answer

S gene

Answer

C gene

Question 8

All of the following are true about HIV infection except?

Accepted Answer

Increased release of acid labile interferon

Answer

Caused by an enveloped RNA virus

Answer

Rate of killing is directly proportional to T4 molecules on the cell surface

Answer

Decreased delayed hypersensitivity activity reaction

Question 9

Which of the following conditions is caused by HHV-8?

Accepted Answer

Kaposi sarcoma

Answer

Burkitt's lymphoma

Answer

Nasopharyngeal carcinoma

Answer

Hepatic carcinoma

Question 10

Influenza pandemics are primarily caused by which type of influenza virus?

Accepted Answer

Type A

Answer

Type B

Answer

Type C

Answer

All types

Virology — MCQs

Virology — MCQs

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