Virology Practice Questions

Q: Herpangina is commonly caused by which virus?

Coxsackie virus B. **Explanation:** **Herpangina** is an acute febrile illness characterized by small vesicular and ulcerative lesions on the posterior oropharynx (tonsillar pillars, soft palate, and uvula). It is primarily caused by **Coxsackievirus Group A** (specifically types A1–A10, A16, and A22). *Note: There appears to be a discrepancy in the provided key. In standard medical microbiology (Jawetz, Harrison, Bailey & Scott), Herpangina is classically associated with **Coxsackievirus Group A**, while Group B is more commonly associated with Pleurodynia and Myocarditis.* **Analysis of Options:** * **Coxsackievirus A (Correct Pathogen):** This is the most common cause of Herpangina and Hand-Foot-Mouth Disease (HFMD). It typically affects children and presents with sudden fever and sore throat. * **Coxsackievirus B:** While it can cause respiratory infections, it is the classic cause of **Bornholm disease (Pleurodynia)**, Myocarditis, and Pericarditis. * **Echovirus:** These can cause aseptic meningitis and non-specific exanthems but are less frequent causes of classic Herpangina. * **Poliovirus:** Primarily causes asymptomatic infection, abortive poliomyelitis, or paralytic disease by affecting the anterior horn cells of the spinal cord. **High-Yield Clinical Pearls for NEET-PG:** * **Herpangina vs. Herpes Stomatitis:** Herpangina lesions are located in the **posterior** pharynx, whereas Gingivostomatitis (HSV-1) typically involves the **anterior** mouth and gums. * **Hand-Foot-Mouth Disease (HFMD):** Most commonly caused by **Coxsackie A16** and **Enterovirus 71**. * **Pleurodynia (Devil’s Grip):** Characterized by paroxysmal thoracic pain, caused by **Coxsackie B**. * **Myocarditis:** Coxsackie B is the most common viral cause of infectious myocarditis.

Q: Which virus can be easily cultured from CSF?

Mumps virus. **Explanation:** The correct answer is **Mumps virus**. In the context of viral meningitis, the ability to isolate a virus from the cerebrospinal fluid (CSF) depends on the duration and magnitude of the viral load during the clinical phase. **Why Mumps virus is correct:** Mumps virus is highly neurotropic. In patients presenting with mumps meningitis, the virus is shed in high titers into the CSF. It can be successfully cultured from the CSF in approximately **50–70% of cases** during the first week of symptoms. This makes it one of the most "culture-positive" viruses in clinical virology compared to other common causes of aseptic meningitis. **Why the other options are incorrect:** * **Poliovirus:** While Poliovirus causes significant CNS pathology (anterior horn cell destruction), it is **rarely isolated from the CSF**. Diagnosis is typically made via stool culture or throat swabs, as the virus replicates in the oropharynx and intestines. * **Coxsackievirus & Echovirus:** These are Enteroviruses. While they are the most common causes of viral meningitis, their isolation rate from CSF is significantly lower than that of Mumps (typically <30-40%). They are more easily recovered from throat swabs or fecal samples. **NEET-PG High-Yield Pearls:** * **Most common cause of viral meningitis:** Enteroviruses (Coxsackie and Echo). * **Mumps Meningitis:** Occurs in up to 15% of mumps cases; it is usually benign and self-limiting. * **CSF Findings in Viral Meningitis:** Lymphocytic pleocytosis, normal glucose, and slightly elevated protein. * **Gold Standard for Enterovirus:** Though culture is possible, **RT-PCR** is now the diagnostic method of choice for all viral CNS infections due to higher sensitivity and speed.

Q: Rotavirus is a double-stranded RNA virus with a double-walled capsid. Which one of the following statements best describes rotavirus?

It is a major cause of neonatal diarrhea. **Explanation:** **Rotavirus** is a member of the *Reoviridae* family, characterized by a segmented, double-stranded RNA genome and a unique wheel-like (rota), triple-layered capsid. **Why Option B is Correct:** Rotavirus is the **most common cause of severe, dehydrating diarrhea** in infants and young children worldwide (typically aged 6 months to 2 years). In the neonatal period, while many infections are asymptomatic due to maternal antibodies, it remains a significant cause of both sporadic cases and outbreaks of neonatal diarrhea in nursery settings. **Analysis of Incorrect Options:** * **Option A:** Rotaviruses are widespread in nature. Many animals (cows, pigs, horses) have their own species-specific rotaviruses. While cross-species transmission is rare, these animal viruses are genetically related to human strains. * **Option C:** Rotavirus is notoriously **difficult to culture** in standard diagnostic laboratories. Diagnosis is typically made using rapid antigen detection (ELISA) or Latex Agglutination from stool samples, or by visualizing "wheel-shaped" particles via Electron Microscopy. * **Option D:** Maternal antibodies (IgG transferred transplacentally and IgA in breast milk) **are protective**. This explains why severe clinical disease is less common in infants under 6 months of age compared to older toddlers. **High-Yield Clinical Pearls for NEET-PG:** * **Genome:** 11 segments of dsRNA (allows for genetic reassortment). * **Pathogenesis:** Produces a viral enterotoxin called **NSP4**, which induces secretion by increasing intracellular calcium. * **Seasonality:** Traditionally peaks in winter months ("Winter diarrhea"). * **Vaccines:** Live attenuated oral vaccines (Rotarix, RotaTeq, and Rotavac) are part of the Universal Immunization Programme (UIP) in India. * **Morphology:** Triple-layered capsid; appears as a "cartwheel" on Electron Microscopy.

Q: Which of the following viruses does not cause chronic hepatitis?

Hepatitis E virus (HEV). **Explanation:** The correct answer is **Hepatitis E virus (HEV)**. The underlying medical concept is the mode of transmission and the nature of the viral infection. HEV is primarily transmitted via the **fecal-oral route** and typically causes an acute, self-limiting infection. In immunocompetent individuals, it does not progress to chronicity. * **Hepatitis E (Option D):** While it is generally acute, a high-yield exception for NEET-PG is that HEV can cause chronic hepatitis **only in immunocompromised individuals** (e.g., organ transplant recipients). However, in the general population, it is not a cause of chronic liver disease. * **Hepatitis B (Option A):** HBV is a DNA virus that can lead to chronic infection in about 5-10% of adults and up to 90% of neonates (vertical transmission). * **Hepatitis C (Option B):** HCV is notorious for chronicity, with approximately **75-85%** of infected individuals developing chronic hepatitis, often leading to cirrhosis and hepatocellular carcinoma. * **Hepatitis D (Option C):** HDV is a defective virus that requires HBV (HBsAg) for replication. Both co-infection and super-infection can lead to chronic states, with super-infection carrying a very high risk of rapid progression to chronic liver failure. **High-Yield Clinical Pearls for NEET-PG:** 1. **HEV in Pregnancy:** HEV (Genotype 1 and 2) is associated with high mortality (up to 20%) in pregnant women due to fulminant hepatic failure. 2. **Vowels to the Bowels:** Hepatitis **A** and **E** are transmitted via the fecal-oral route and generally do not cause chronic disease. 3. **Consonants to the Blood:** Hepatitis **B, C, and D** are transmitted parenterally and are the primary causes of chronic hepatitis.

Q: Laryngeal papillomas are caused by which Human Papillomavirus (HPV) types?

6, 11. **Explanation:** Laryngeal papillomatosis (also known as Recurrent Respiratory Papillomatosis or RRP) is the most common benign neoplasm of the larynx. It is caused by the **Human Papillomavirus (HPV)**, specifically **Types 6 and 11**. These are classified as "low-risk" HPV types because they primarily cause benign epithelial proliferations (warts) rather than malignancies. Type 11 is clinically significant as it is often associated with a more aggressive clinical course and more frequent recurrences. **Analysis of Options:** * **Option A (6, 11):** Correct. These types are responsible for over 90% of laryngeal papillomas in both juvenile and adult-onset forms. * **Option B (16, 18):** Incorrect. These are "high-risk" oncogenic types. While they are the primary cause of cervical cancer and oropharyngeal squamous cell carcinoma, they are rarely the primary cause of benign laryngeal papillomas. * **Option C (33, 45):** Incorrect. These are also high-risk oncogenic types associated with various anogenital and mucosal cancers. * **Option D (4, 27):** Incorrect. These types are typically associated with common cutaneous warts (Verruca vulgaris) on the hands and feet. **High-Yield Clinical Pearls for NEET-PG:** * **Bimodal Distribution:** RRP has two peaks—Juvenile (age <5, usually via vertical transmission during birth) and Adult (age 20-40). * **Classic Presentation:** Progressive hoarseness (most common) and stridor (in advanced cases). * **Morphology:** Exophytic, "cauliflower-like" sessile or pedunculated masses, most commonly on the true vocal cords. * **Treatment:** The gold standard is **CO2 Laser excision** or microdebrider excision. Note that medical therapies (e.g., Cidofovir, Interferon) are adjunctive, not curative. * **Malignant Transformation:** Rare (<3%), but when it occurs, it is often associated with HPV-16 or 18, or history of prior irradiation.

Q: Which serotype of Dengue virus is considered the most virulent?

Dengue virus serotype 2. **Explanation:** **Dengue virus (DENV)** is a single-stranded RNA virus belonging to the family *Flaviviridae*, with four distinct serotypes (DENV-1 to DENV-4). While all serotypes can cause disease, **Dengue virus serotype 2 (DENV-2)** is clinically recognized as the most virulent. **Why DENV-2 is the correct answer:** Epidemiological studies and clinical data consistently link DENV-2 to more severe disease manifestations, such as **Dengue Hemorrhagic Fever (DHF)** and **Dengue Shock Syndrome (DSS)**. DENV-2 is associated with higher viral loads and a more robust inflammatory response. Furthermore, it is the serotype most frequently implicated in secondary infections where **Antibody-Dependent Enhancement (ADE)** occurs—a process where non-neutralizing antibodies from a previous infection (usually DENV-1) facilitate the entry of DENV-2 into host macrophages, leading to a "cytokine storm." **Analysis of Incorrect Options:** * **DENV-1:** Often associated with primary infections and large outbreaks, but generally results in classic Dengue Fever rather than severe complications. * **DENV-3:** Known to cause severe disease and neurological manifestations, but statistically ranks behind DENV-2 in terms of global virulence and shock syndrome frequency. * **DENV-4:** Generally considered the least virulent serotype, often resulting in milder clinical symptoms. **High-Yield Clinical Pearls for NEET-PG:** * **Vector:** *Aedes aegypti* (primary) and *Aedes albopictus*. * **Most common serotype in India:** Historically DENV-2, though DENV-1 and DENV-3 also circulate widely. * **Diagnosis:** NS1 Antigen (Days 1–5); IgM/IgG ELISA (after Day 5). * **Tourniquet Test:** A positive test (≥10 petechiae per square inch) is a classic bedside indicator of capillary fragility in Dengue. * **ADE Phenomenon:** Explains why a second infection with a *different* serotype is more dangerous than the first.

Q: Parvovirus causes all of the following except?

Roseola infantum. **Explanation:** The correct answer is **Roseola infantum** because it is caused by **Human Herpesvirus 6 (HHV-6)**, and occasionally HHV-7, not Parvovirus B19. Roseola typically presents in infants with a high fever followed by the sudden appearance of a maculopapular rash as the fever subsides. **Analysis of Options:** * **A. Aplastic anemia:** Parvovirus B19 infects and lyses **erythroid progenitor cells** in the bone marrow. In patients with high red cell turnover (e.g., Sickle Cell Disease, Spherocytosis), this leads to a life-threatening **Transient Aplastic Crisis**. * **B. Erythema infectiosum (Fifth Disease):** This is the most common clinical presentation of Parvovirus B19 in children, characterized by the classic **"slapped-cheek" appearance** followed by a reticular (lace-like) body rash. * **D. Arthralgia:** In adults (especially women), Parvovirus B19 infection often presents as acute, symmetrical polyarthritis involving the small joints of the hands, mimicking Rheumatoid Arthritis. **High-Yield Clinical Pearls for NEET-PG:** * **Receptor:** Parvovirus B19 binds to the **P-antigen** (globoside) on erythroblasts. * **Hydrops Fetalis:** If a pregnant woman is infected, the virus can cross the placenta, causing severe fetal anemia, high-output cardiac failure, and fetal hydrops. * **Virology:** Parvovirus is the **smallest DNA virus** and is unique for being **Single-Stranded (ssDNA)** and non-enveloped. * **Pure Red Cell Aplasia:** Can occur in immunocompromised individuals (e.g., HIV patients) due to chronic Parvovirus B19 infection.

Q: Which of the following statements regarding the prion protein is true?

It catalyzes the abnormal folding of other proteins.. **Explanation** Prions (Proteinaceous Infectious Particles) are unique pathogens because they lack nucleic acids (DNA or RNA). The correct answer is **Option B** because the pathogenesis of prion diseases (like Creutzfeldt-Jakob Disease) centers on the **conformational change** of the normal cellular prion protein ($PrP^C$) into an abnormal, misfolded isoform ($PrP^{Sc}$). 1. **Mechanism of Action:** $PrP^{Sc}$ acts as a template. When it comes into contact with normal $PrP^C$ (which is rich in alpha-helices), it catalyzes its conversion into the infectious $PrP^{Sc}$ form (rich in beta-pleated sheets). This creates a self-propagating cascade leading to protein aggregation and neurodegeneration. **Analysis of Incorrect Options:** * **Option A:** Prions are **not** coded by viral DNA. They are encoded by the host's own genome (the *PRNP* gene on chromosome 20). * **Option C:** Prions do not have a primary role in protecting disulfide bonds. In fact, the transition from $PrP^C$ to $PrP^{Sc}$ involves significant structural destabilization and the formation of insoluble amyloid plaques. * **Option D:** Prions do not act as proteases (enzymes that cleave proteins). Instead, $PrP^{Sc}$ is notoriously **resistant to proteases** (Protease K resistant), which allows it to accumulate in the brain. **High-Yield Clinical Pearls for NEET-PG:** * **Structure:** $PrP^C$ (Alpha-helix) $\rightarrow$ $PrP^{Sc}$ (Beta-sheet). * **Resistance:** Prions are highly resistant to standard sterilization (autoclaving, UV light, and formalin). They require **1N NaOH for 1 hour** or **porous load autoclaving at 134°C**. * **Histology:** Characterized by "spongiform encephalopathy" (vacuolation of neurons) without an inflammatory response. * **Diagnosis:** Detection of **14-3-3 protein** in CSF is a key marker for CJD.

Q: Which of the following produces pocks on the chorioallantoic membrane of a chick embryo?

Herpes simplex. **Explanation:** The cultivation of viruses in embryonated eggs is a classic virological technique. The **Chorioallantoic Membrane (CAM)** is specifically used for the growth of viruses that produce visible lesions called **pocks**. Each pock represents a single infectious virus particle, and their morphology (size, shape, and color) helps in identification. **Why Herpes simplex is correct:** **Herpes Simplex Virus (HSV)**, along with Poxviruses (like Variola and Vaccinia), is characterized by its ability to produce distinct pocks on the CAM. HSV typically produces small, white, non-necrotic pocks. This is a high-yield diagnostic feature used to differentiate it from other members of the Herpes family. **Why the other options are incorrect:** * **Myxoviruses (Influenza/Mumps):** These are typically grown in the **allantoic or amniotic cavity**, not the CAM. They do not produce pocks; their growth is detected via hemagglutination. * **Varicella-Zoster Virus (VZV):** Unlike HSV, VZV is highly cell-associated and does not grow well in embryonated eggs or produce pocks on the CAM. * **Cytomegalovirus (CMV):** CMV is highly species-specific and only grows in human fibroblast cell cultures. It does not grow on the CAM of a chick embryo. **High-Yield NEET-PG Pearls:** 1. **Pock-forming viruses:** Variola (large, opaque), Vaccinia (large, necrotic), and HSV (small, white). 2. **Amniotic cavity:** Primary site for the initial isolation of the Influenza virus. 3. **Allantoic cavity:** Used for the production of vaccines (Yellow fever, Influenza). 4. **Yolk sac:** Used for cultivating Chlamydia, Rickettsia, and some viruses (e.g., Hantavirus).

Question 1

Which of the following statements best describes subacute sclerosing panencephalitis (SSPE) virus?

Accepted Answer

It is a progressive disease involving both white and gray matter.

Answer

It is a late central nervous system manifestation of mumps.

Answer

It is a common event occurring in 1 of 300,000 cases of mumps.

Answer

Viral DNA can be demonstrated in brain cells.

Question 2

Herpangina is commonly caused by which virus?

Accepted Answer

Coxsackie virus B

Answer

Coxsackie virus A

Answer

Echovirus

Answer

Poliovirus

Question 3

Which virus can be easily cultured from CSF?

Accepted Answer

Mumps virus

Answer

Poliovirus

Answer

Coxsackievirus

Answer

Echovirus

Question 4

Rotavirus is a double-stranded RNA virus with a double-walled capsid. Which one of the following statements best describes rotavirus?

Accepted Answer

It is a major cause of neonatal diarrhea

Answer

There are no related animal viruses

Answer

It is readily cultured from the stool of infected persons

Answer

Maternal antibody does not appear to be protective

Question 5

Which of the following viruses does not cause chronic hepatitis?

Accepted Answer

Hepatitis E virus (HEV)

Answer

Hepatitis B virus (HBV)

Answer

Hepatitis C virus (HCV)

Answer

Hepatitis D virus (HDV)

Question 6

Laryngeal papillomas are caused by which Human Papillomavirus (HPV) types?

Accepted Answer

6, 11

Answer

16, 18

Answer

33, 45

Answer

4, 27

Question 7

Which serotype of Dengue virus is considered the most virulent?

Accepted Answer

Dengue virus serotype 2

Answer

Dengue virus serotype 1

Answer

Dengue virus serotype 3

Answer

Dengue virus serotype 4

Question 8

Parvovirus causes all of the following except?

Accepted Answer

Roseola infantum

Answer

Aplastic anemia

Answer

Erythema infectiosum

Answer

Arthralgia

Question 9

Which of the following statements regarding the prion protein is true?

Accepted Answer

It catalyzes the abnormal folding of other proteins.

Answer

It is a protein product coded in viral DNA.

Answer

It protects disulfide bonds from oxidation.

Answer

It cleaves normal proteins.

Question 10

Which of the following produces pocks on the chorioallantoic membrane of a chick embryo?

Accepted Answer

Herpes simplex

Answer

Myxovirus

Answer

Varicella

Answer

Cytomegalovirus

Virology — MCQs

Virology — MCQs

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