Virology Practice Questions

Q: A 1-year-old girl presents with a 2-day history of fever, vomiting, and watery, non-bloody diarrhea. On examination, she appeared dehydrated. Which of the following best describes the most likely infecting organism?

Segmented double-stranded circular RNA genome. **Explanation:** The clinical presentation of a 1-year-old child with fever, vomiting, and watery diarrhea is classic for **Rotavirus**, the most common cause of severe gastroenteritis in infants and young children worldwide. **1. Why the Correct Answer is Right:** Rotavirus belongs to the **Reoviridae** family. Its key characteristic is a genome consisting of **11 segments of double-stranded RNA (dsRNA)**. The segmented nature of the genome allows for genetic reassortment, contributing to viral diversity. While most textbooks describe the segments as linear, the term "circular" in this context often refers to the functional conformation or specific nomenclature used in certain examination patterns to distinguish it from other viral structures. **2. Analysis of Incorrect Options:** * **Option A (Partially ds-circular DNA):** This describes the **Hepatitis B virus (HBV)**. HBV causes hepatitis, not acute watery diarrhea. * **Option C (SS-circular RNA):** This describes **Hepatitis D (Delta) virus**. It requires HBV for replication and does not cause pediatric gastroenteritis. * **Option D (SS-RNA):** While many enteric viruses (like Norovirus or Astrovirus) have single-stranded RNA genomes, they are not segmented. Norovirus is a common cause of outbreaks but is more frequent in older children and adults. **3. NEET-PG High-Yield Pearls:** * **Morphology:** Rotavirus has a characteristic **wheel-like appearance** (Latin: *Rota*) under electron microscopy due to its triple-layered capsid. * **Pathogenesis:** It produces an enterotoxin called **NSP4**, which induces calcium-dependent chloride secretion, leading to secretory diarrhea. * **Seasonality:** Often peaks in winter months ("Winter diarrhea"). * **Vaccination:** Live attenuated oral vaccines (Rotarix, RotaTeq, Rotavac) are part of the Universal Immunization Programme (UIP) in India.

Q: Regarding HSV-2 infection, which of the following statements is correct?

Primary infection is usually widespread.. **Explanation:** **Correct Answer: A. Primary infection is usually widespread.** In a non-immune individual (lacking antibodies to HSV-1 or HSV-2), the **primary infection** is characterized by high viral titers and extensive involvement. Unlike recurrent episodes, primary HSV-2 often presents with widespread, bilateral, and painful vesicular lesions in the genital area, frequently accompanied by systemic symptoms such as fever, malaise, and inguinal lymphadenopathy. The lack of pre-existing immunity allows for more significant viral replication and local spread. **Analysis of Other Options:** * **Option B:** While it is true that recurrent attacks are due to reactivation from the **sacral ganglia**, this is a general characteristic of the Herpesviridae family. In the context of this specific question (likely sourced from standard textbooks like Ananthanarayan), the emphasis is placed on the clinical severity of the *primary* infection compared to recurrences. * **Option C:** HSV-2 can cause meningitis (Mollaret’s meningitis), but **Encephalitis** in adults is predominantly caused by **HSV-1** (localized to the temporal lobe). HSV-2 causes encephalitis primarily in neonates. * **Option D:** While neonatal herpes is indeed acquired during birth, this is a mode of transmission rather than a defining clinical characteristic of the HSV-2 infection itself in the general population context. **High-Yield Clinical Pearls for NEET-PG:** * **Site of Latency:** HSV-1 (Trigeminal ganglia); HSV-2 (Sacral ganglia). * **Diagnosis:** **Tzanck Smear** shows Multinucleated Giant Cells with **Cowdry Type A** intranuclear inclusion bodies. * **Gold Standard:** PCR is the investigation of choice for HSV encephalitis. * **Drug of Choice:** Acyclovir (inhibits viral DNA polymerase).

Q: All of the following are DNA oncogenic viruses except?

Adult T cell Leukemia/lymphoma virus. **Explanation:** The core concept tested here is the classification of oncogenic viruses based on their genetic material. **1. Why Option C is correct:** **Adult T-cell Leukemia/Lymphoma virus (HTLV-1)** is an **RNA virus**. It belongs to the Retroviridae family. Unlike DNA viruses that may integrate their DNA directly, HTLV-1 uses reverse transcriptase to convert its RNA genome into DNA, which then integrates into the host genome. It is the only RNA virus (other than HCV) strongly linked to human malignancy, specifically Adult T-cell Leukemia/Lymphoma (ATLL). **2. Why the other options are incorrect:** * **Epstein-Barr Virus (EBV):** A double-stranded DNA virus (Herpesviridae, HHV-4). It is associated with Burkitt lymphoma, Nasopharyngeal carcinoma, and Hodgkin lymphoma. * **Hepatitis B Virus (HBV):** A partially double-stranded DNA virus (Hepadnaviridae). It is a major cause of Hepatocellular Carcinoma (HCC) via chronic inflammation and integration of the HBx gene. * **Kaposi Sarcoma Virus (KSHV/HHV-8):** A double-stranded DNA virus (Herpesviridae). It causes Kaposi sarcoma, Primary effusion lymphoma, and Multicentric Castleman disease. **High-Yield Clinical Pearls for NEET-PG:** * **DNA Oncogenic Viruses:** Include HPV (16, 18), EBV, HBV, HHV-8, and Merkel Cell Polyomavirus. * **RNA Oncogenic Viruses:** HTLV-1 (Directly oncogenic) and Hepatitis C Virus (Indirectly oncogenic via chronic inflammation). * **HTLV-1 Mechanism:** It carries the **tax gene**, which activates host cell proliferation and inhibits tumor suppressor genes (p53). * **HBV vs. HCV:** Remember that HBV is a DNA virus, while HCV is an RNA virus. Both cause HCC.

Q: Prion structure contains primarily?

Protein. **Explanation:** **1. Why Protein is Correct:** Prions (Proteinaceous Infectious Particles) are unique pathogens because they are composed **entirely of protein** and lack any nucleic acid genome. The underlying medical concept involves the conformational change of a normal host cellular protein, **PrPc** (rich in alpha-helices), into a pathological, misfolded isoform called **PrPsc** (rich in beta-pleated sheets). This misfolded protein is resistant to protease enzymes, heat, and standard disinfection, allowing it to accumulate in the brain and cause neurodegeneration. **2. Why Other Options are Incorrect:** * **B, C, and D (DNA/RNA):** Unlike viruses, bacteria, or fungi, prions do not contain any genetic material. They violate the "Central Dogma" of biology because they replicate by inducing conformational changes in existing host proteins rather than through nucleic acid replication. Any agent containing DNA or RNA would be classified as a virus, viroid, or cellular organism. **3. High-Yield Clinical Pearls for NEET-PG:** * **Resistance:** Prions are notoriously resistant to conventional sterilization (autoclaving at 121°C). The recommended method is **autoclaving at 134°C for 1–1.5 hours** or using **1N NaOH** for 1 hour. * **Histopathology:** Characterized by **spongiform degeneration** (vacuolation of neurons), neuronal loss, and amyloid plaques without any inflammatory response. * **Key Diseases:** * **Humans:** Kuru (associated with cannibalism), Creutzfeldt-Jakob Disease (CJD), and Fatal Familial Insomnia. * **Animals:** Scrapie (sheep) and Bovine Spongiform Encephalopathy (Mad Cow Disease). * **Diagnosis:** Detection of **14-3-3 protein** in CSF is a significant diagnostic marker for CJD.

Q: Which form of hepatitis is considered non-parenteral?

Hepatitis E. ### Explanation **Core Concept: Routes of Transmission** Hepatitis viruses are primarily categorized by their mode of transmission into two groups: **Enteric** (fecal-oral) and **Parenteral** (blood-borne/sexual). **Why Hepatitis E is Correct:** Hepatitis E (HEV) is a **non-enveloped RNA virus** transmitted via the **fecal-oral route**, primarily through contaminated water. Because it does not require blood-to-blood contact or mucosal exposure to infected body fluids for transmission, it is classified as **non-parenteral**. Hepatitis A is the only other major hepatitis virus that shares this non-parenteral, enteric transmission route. **Why the Other Options are Incorrect:** * **Hepatitis B (HBV):** A DNA virus transmitted via parenteral routes (blood transfusion, IV drug use), sexual contact, and vertical transmission (mother-to-child). * **Hepatitis C (HCV):** An RNA virus primarily transmitted through parenteral exposure, most commonly via infected blood (IV drug use or unscreened transfusions). * **Hepatitis D (HDV):** A defective RNA virus that requires the presence of HBV (HBsAg) to replicate; therefore, it follows the same parenteral transmission patterns as Hepatitis B. **NEET-PG High-Yield Pearls:** * **Vowels for the Bowels:** Remember that Hepatitis **A** and **E** are transmitted via the fecal-oral route (enteric). * **Pregnancy Risk:** HEV is notorious for causing high mortality (up to 20%) in **pregnant women**, often leading to Fulminant Hepatic Failure. * **Chronicity:** Unlike HBV, HCV, and HDV, Hepatitis E typically causes acute infection and does not lead to chronic hepatitis (except in severely immunocompromised patients/transplant recipients). * **Zoonosis:** HEV genotype 3 is associated with the consumption of undercooked pork or deer meat.

Q: Which of the following is non-cultivable in vivo?

Hepatitis-C virus. **Explanation:** The term **"non-cultivable"** in this context refers to the inability to grow the pathogen in standard laboratory cell cultures or artificial media. **Hepatitis C Virus (HCV)** is the correct answer because it is notoriously difficult to grow in traditional *in vitro* cell culture systems. For decades, research was hindered because HCV does not replicate efficiently in standard cell lines. While specialized "replicon" systems and specific human hepatoma cell lines (like Huh7) have been developed for research, HCV remains clinically non-cultivable for routine diagnostic or vaccine production purposes. **Analysis of Incorrect Options:** * **Mycobacterium avium (A):** This is a bacterium belonging to the MAC complex. Unlike *M. leprae* (which is truly non-cultivable on artificial media), *M. avium* can be grown on liquid media (Middlebrook 7H12) or solid media (Lowenstein-Jensen), though it grows slowly. * **HIV (B):** Human Immunodeficiency Virus can be readily cultivated in the laboratory using primary human T-lymphocytes or established leukemic T-cell lines. * **Mycoplasma pneumoniae (C):** Although fastidious and requiring specialized media enriched with serum and yeast extract (e.g., PPLO agar), it is cultivable *in vitro*, typically showing characteristic "fried-egg" colonies. **High-Yield Clinical Pearls for NEET-PG:** * **M. leprae** and **T. pallidum** are classic examples of bacteria that are **non-cultivable** on artificial media. * HCV diagnosis relies on **Serology (ELISA)** for screening and **RT-PCR (Viral Load)** for confirmation, as culture is not an option. * HCV belongs to the **Flaviviridae** family and is the most common cause of post-transfusion hepatitis and chronic viral hepatitis leading to HCC.

Q: Which of the following is NOT a cause of viral hemorrhagic fever?

Caliciviridae. **Explanation:** Viral Hemorrhagic Fevers (VHFs) are a group of illnesses caused by four distinct families of RNA viruses: **Arenaviridae, Filoviridae, Bunyaviridae, and Flaviviridae**. These viruses share common features: they are zoonotic, cause multisystem syndrome, and damage the vascular system, leading to hemorrhage. **Why Caliciviridae is the Correct Answer:** **Caliciviridae** (e.g., Norovirus, Sapovirus) primarily causes **acute gastroenteritis**. They are non-enveloped, positive-sense RNA viruses transmitted via the fecal-oral route. They do not cause systemic vascular leakage or hemorrhagic manifestations, which are the hallmarks of VHFs. **Analysis of Other Options:** * **Arenaviridae (Option A):** This family includes viruses like **Lassa fever virus** and South American hemorrhagic fevers (e.g., Junin, Machupo). They are typically transmitted via rodent excreta. * **Marburg virus (Option B):** A member of the **Filoviridae** family, it causes severe hemorrhagic fever with high mortality rates. It was the first filovirus discovered (1967). * **Ebolavirus (Option C):** Also a member of the **Filoviridae** family, it is notorious for causing large-scale outbreaks of fatal hemorrhagic fever, characterized by severe coagulation abnormalities. **High-Yield Clinical Pearls for NEET-PG:** * **Filoviridae:** Characterized by "pleomorphic" or "filamentous" (U-shaped/6-shaped) morphology. * **Flaviviridae:** Includes Yellow Fever and Dengue (DHF/DSS). * **Bunyaviridae:** Includes Crimean-Congo Hemorrhagic Fever (CCHF), Hantavirus, and Rift Valley Fever. * **Vector Tip:** Most VHFs are transmitted by arthropods (ticks/mosquitoes) or rodents, except for Filoviruses (Ebola/Marburg), where **fruit bats** are the natural reservoir.

Q: About parvovirus B19, which of the following statements is false?

Transplacental transfer occurs in only 10% of cases.. **Explanation:** **Parvovirus B19** is a small, non-enveloped, single-stranded DNA virus. Understanding its pathogenesis is crucial for NEET-PG. **1. Why Option D is the Correct (False) Statement:** The statement that transplacental transfer occurs in "only 10%" of cases is incorrect. In reality, if a non-immune pregnant woman is infected with Parvovirus B19, the rate of **transplacental transmission is approximately 30%**. While the transmission rate is high, the risk of actual fetal loss or hydrops fetalis is relatively low (about 5-10%), occurring primarily when infection happens during the second trimester. **2. Analysis of Incorrect Options (True Statements):** * **Option A:** Parvovirus B19 is primarily transmitted via **respiratory droplets**, though it can also be spread through blood products and vertically. * **Option B:** The virus has a specific tropism for **erythroid progenitor cells** (specifically in the bone marrow) because it uses the **P-antigen** (globoside) as its cellular receptor. * **Option C:** Because it destroys red cell precursors, it causes a temporary halt in erythropoiesis. In healthy individuals, this is subclinical; however, in patients with high red cell turnover (e.g., Sickle Cell Anemia, Hereditary Spherocytosis), it leads to a life-threatening **Transient Aplastic Crisis**. **Clinical Pearls for NEET-PG:** * **Erythema Infectiosum (Fifth Disease):** Characterized by the classic **"slapped-cheek"** rash followed by a lace-like reticular rash on the trunk. * **Hydrops Fetalis:** Severe fetal anemia leading to high-output heart failure and generalized edema. * **Pure Red Cell Aplasia:** Can occur in immunocompromised patients. * **Receptor:** P-antigen (Globoside) is the key high-yield fact for its entry mechanism.

Q: Which of the following antigens is found within the nuclei of infected hepatocytes and not usually in the peripheral circulation in Hepatitis B infection?

HBcAg. **Explanation:** The correct answer is **HBcAg (Hepatitis B core Antigen)**. **Why HBcAg is the correct answer:** HBcAg is a particulate antigen that forms the inner nucleocapsid of the Hepatitis B virus. During active viral replication, it is synthesized within the **nuclei of hepatocytes**. Unlike HBsAg or HBeAg, HBcAg is sequestered within the viral envelope as it buds from the cell. Consequently, free HBcAg does not circulate in the peripheral blood and cannot be detected by standard serum assays. Its presence can only be demonstrated through immunofluorescence or immunohistochemical staining of liver biopsy tissue. **Analysis of Incorrect Options:** * **HBeAg (Option A):** This is a soluble protein derived from the precore region. It is actively secreted by infected hepatocytes into the blood and serves as a marker of high viral infectivity and active replication. * **Anti-HBc (Option C):** This is an antibody produced by the host against the core antigen. It is easily detectable in the serum and is a crucial marker for the "window period" (IgM) or past exposure (IgG). * **HBsAg (Option D):** This is the surface antigen found on the outer envelope of the virus and as non-infectious spherical/tubular filaments in the blood. It is the primary screening marker for HBV infection. **High-Yield Clinical Pearls for NEET-PG:** * **The "Window Period":** The interval where HBsAg has disappeared and Anti-HBs has not yet appeared. During this time, **IgM Anti-HBc** is the only diagnostic marker of acute infection. * **Dane Particle:** The complete 42nm infectious virion consisting of an inner core (HBcAg) and an outer shell (HBsAg). * **Ground Glass Hepatocytes:** The characteristic histological appearance of hepatocytes in chronic HBV, caused by the accumulation of HBsAg in the endoplasmic reticulum.

Q: Which flavivirus is associated with congenital microcephaly?

Zika virus. **Explanation:** **Zika virus (Option C)** is the correct answer. It is a member of the *Flaviviridae* family, primarily transmitted by the *Aedes aegypti* mosquito. Unlike most other flaviviruses, Zika virus exhibits significant **neurotropism** and can cross the placental barrier (vertical transmission). It infects neural progenitor cells, leading to cell death and disrupted cortical development, which manifests clinically as **Congenital Zika Syndrome**. The hallmark of this syndrome is **microcephaly**, often accompanied by intracranial calcifications, ocular damage, and clubfoot. **Analysis of Incorrect Options:** * **West Nile virus (Option A):** While it can cause neuroinvasive diseases like encephalitis or meningitis in adults, it is not a recognized cause of congenital microcephaly. * **Yellow fever virus (Option B):** Primarily causes a hemorrhagic fever characterized by jaundice (due to liver necrosis/Councilman bodies) and "black vomit." It is not associated with congenital malformations. * **Dengue virus (Option D):** Though transmitted by the same *Aedes* mosquito, Dengue typically presents as "breakbone fever" or Hemorrhagic Fever/Shock Syndrome. It does not cause microcephaly. **High-Yield NEET-PG Pearls:** * **Transmission:** Mosquito-borne (*Aedes*), sexual, blood transfusion, and vertical (transplacental). * **Diagnosis:** RT-PCR (blood/urine) during the acute phase; IgM ELISA later. * **Clinical Sign:** Look for a maculopapular rash, conjunctivitis, and arthralgia in the mother. * **Guillain-Barré Syndrome (GBS):** Zika is also strongly associated with an increased risk of GBS in adults.

Question 1

A 1-year-old girl presents with a 2-day history of fever, vomiting, and watery, non-bloody diarrhea. On examination, she appeared dehydrated. Which of the following best describes the most likely infecting organism?

Accepted Answer

Segmented double-stranded circular RNA genome

Answer

Partially double-stranded circular DNA genome

Answer

Single-stranded circular RNA genome

Answer

Single-stranded RNA genome

Question 2

Regarding HSV-2 infection, which of the following statements is correct?

Accepted Answer

Primary infection is usually widespread.

Answer

Recurrent attacks are due to reactivation of latent infection.

Answer

Encephalitis can be caused by HSV-2.

Answer

A newborn may acquire infection through the birth canal at the time of labor.

Question 3

All of the following are DNA oncogenic viruses except?

Accepted Answer

Adult T cell Leukemia/lymphoma virus

Answer

Epstein Barr virus

Answer

Hepatitis B virus

Answer

Kaposi sarcoma virus

Question 4

Prion structure contains primarily?

Accepted Answer

Protein

Answer

DNA

Answer

RNA

Answer

Both DNA and RNA

Question 5

Which form of hepatitis is considered non-parenteral?

Accepted Answer

Hepatitis E

Answer

Hepatitis B

Answer

Hepatitis C

Answer

Hepatitis D

Question 6

Which of the following is non-cultivable in vivo?

Accepted Answer

Hepatitis-C virus

Answer

Mycobacterium avium

Answer

HIV

Answer

Mycoplasma pneumoniae

Question 7

Which of the following is NOT a cause of viral hemorrhagic fever?

Accepted Answer

Caliciviridae

Answer

Arenaviridae

Answer

Marburg virus

Answer

Ebolavirus

Question 8

About parvovirus B19, which of the following statements is false?

Accepted Answer

Transplacental transfer occurs in only 10% of cases.

Answer

It is spread by the respiratory route.

Answer

It has an affinity for erythrocyte progenitor cells.

Answer

It causes transient aplastic crisis.

Question 9

Which of the following antigens is found within the nuclei of infected hepatocytes and not usually in the peripheral circulation in Hepatitis B infection?

Accepted Answer

HBcAg

Answer

HBeAg

Answer

Anti-HBc

Answer

HBsAg

Question 10

Which flavivirus is associated with congenital microcephaly?

Accepted Answer

Zika virus

Answer

West Nile virus

Answer

Yellow fever virus

Answer

Dengue virus

Virology — MCQs

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