Virology Practice Questions

Q: Suckling mice are used for the isolation of which of the following viruses?

Coxsackie virus. **Explanation:** The use of **suckling mice** (mice less than 48 hours old) is a classic method for isolating specific viruses that do not grow well in standard cell cultures or embryonated eggs. **1. Why Coxsackie virus is correct:** Coxsackie viruses (members of the *Picornaviridae* family) are traditionally classified based on their histopathological effects in suckling mice: * **Group A:** Causes widespread **flaccid paralysis** due to generalized myositis of skeletal muscles. * **Group B:** Causes **spastic paralysis** due to focal myositis and necrotizing steatitis (inflammation of brown fat), as well as encephalitis and pancreatitis. This differential pathology in suckling mice remains a hallmark of Coxsackie virus identification. **2. Why the other options are incorrect:** * **Pox virus:** These are typically isolated using the **Chorioallantoic Membrane (CAM)** of embryonated chicken eggs, where they produce characteristic visible lesions called **pocks**. * **Herpes virus:** While they can grow on CAM (producing small pocks), they are most commonly isolated using **cell cultures** (e.g., human fibroblast lines), where they produce rapid cytopathic effects (CPE) like Cowdry Type A inclusion bodies. * **Adenovirus:** These are best isolated in **continuous epithelial cell lines** (e.g., HeLa, HEp-2), showing characteristic "grape-like clusters" as CPE. **High-Yield Clinical Pearls for NEET-PG:** * **Arboviruses** (like Dengue and Japanese Encephalitis) are also frequently isolated by intracerebral inoculation in suckling mice. * **Rabies virus** diagnosis via the **Mouse Inoculation Test** is considered a gold standard confirmatory test (though largely replaced by FAT). * Remember: **Group A** = **A**ll muscle (Flaccid); **Group B** = **B**ody/Brain/Brown fat (Spastic).

Q: A 1-year-old child develops voluminous watery diarrhea and vomiting. Which of the following viruses is the most likely cause of the child's diarrhea?

Rotavirus. **Explanation:** **Rotavirus** is the most common cause of severe, dehydrating diarrhea in infants and young children worldwide (typically aged 6 months to 2 years). It primarily infects the mature enterocytes of the small intestine, leading to malabsorption and osmotic diarrhea. A key high-yield feature is the production of **NSP4 enterotoxin**, which induces secretory diarrhea by increasing intracellular calcium levels. The clinical presentation typically begins with vomiting, followed by profuse watery diarrhea and low-grade fever. **Analysis of Incorrect Options:** * **A. Coronavirus:** While some strains (like SARS-CoV-2) can cause GI symptoms, they are primarily respiratory pathogens and not the leading cause of infantile viral gastroenteritis. * **B. Lymphocytic choriomeningitis virus (LCMV):** This is an arenavirus transmitted by rodents. It typically causes a flu-like illness or aseptic meningitis/encephalitis, not watery diarrhea. * **C. Norwalk agent (Norovirus):** This is the leading cause of gastroenteritis outbreaks across all age groups (especially in schools, cruise ships, and nursing homes). While it causes similar symptoms, Rotavirus remains the more frequent culprit in the specific **1-year-old** age demographic. **Clinical Pearls for NEET-PG:** * **Mechanism:** Villous atrophy and NSP4 enterotoxin. * **Seasonality:** More common in winter months ("Winter diarrhea"). * **Diagnosis:** Latex agglutination or ELISA for viral antigen in stools. * **Prevention:** Live attenuated oral vaccines (Rotarix, RotaTeq, or Rotavac) are part of the National Immunization Schedule. * **Treatment:** Rehydration (ORS/IV fluids) is the mainstay; antibiotics are not indicated.

Q: Echoviruses are cytopathogenic human viruses that mainly infect which system?

Intestinal tract. **Explanation:** **Echoviruses** (Enteric Cytopathic Human Orphan viruses) belong to the genus *Enterovirus* within the family *Picornaviridae*. The correct answer is the **Intestinal tract** because, like other enteroviruses (Poliovirus, Coxsackievirus), Echoviruses primarily replicate in the mucosal cells of the **gastrointestinal tract** and the nasopharynx. They are transmitted via the fecal-oral route and are shed in the feces for several weeks, making the gut their primary site of infection and colonization. **Analysis of Options:** * **A. Respiratory system:** While Echoviruses can cause minor upper respiratory symptoms, it is not their primary site of infection or replication. * **B. Central nervous system:** This is a common site of **secondary** involvement. Echoviruses are a leading cause of aseptic meningitis, but they reach the CNS only after primary replication in the gut and subsequent viremia. * **C. Blood and lymphatic systems:** These serve as the **route of dissemination** (viremia) to target organs like the skin, heart, or meninges, rather than being the primary site of infection. **High-Yield Clinical Pearls for NEET-PG:** * **Nomenclature:** The name "Orphan" was originally given because these viruses were not initially associated with any specific disease. * **Clinical Spectrum:** They are the most common cause of **aseptic (viral) meningitis** and can cause neonatal sepsis-like syndromes, exanthems (rashes), and infantile diarrhea. * **Diagnosis:** Viral culture (showing characteristic cytopathic effects) or PCR from stool or CSF is the gold standard. * **Acid Stability:** Like all enteroviruses, Echoviruses are acid-stable, allowing them to survive the gastric pH to reach the intestinal tract.

Q: Negri bodies in brain are characteristically seen in which of the following conditions?

Rabies. **Explanation:** **Negri bodies** are the hallmark histopathological finding in **Rabies**, caused by the Rabies virus (a Rhabdovirus). These are pathognomonic **intracytoplasmic, eosinophilic, round-to-oval inclusion bodies** found in the cytoplasm of neurons. They represent sites of viral replication and are most commonly observed in the **Purkinje cells of the cerebellum** and the **pyramidal cells of the hippocampus (Ammon’s horn)**. **Analysis of Options:** * **Botulism (A):** Caused by *Clostridium botulinum* toxin, which inhibits acetylcholine release at the neuromuscular junction. It does not produce inclusion bodies and primarily affects peripheral nerves, not brain parenchyma. * **Chickenpox (B):** Caused by Varicella-Zoster Virus (VZV). While it can cause encephalitis, the characteristic inclusions are **Cowdry Type A** (intranuclear), not Negri bodies. * **Herpes Encephalitis (D):** Caused by HSV-1. It typically presents with hemorrhagic necrosis of the temporal lobes. Histologically, it shows **Cowdry Type A intranuclear inclusions** (Lipschütz bodies), not cytoplasmic inclusions. **High-Yield Clinical Pearls for NEET-PG:** * **Morphology:** Negri bodies contain viral nucleocapsids and appear as eosinophilic structures with internal "basophilic granules." * **Staining:** Best visualized using **Sellers stain** (basic fuchsin and methylene blue) or Mann’s stain. * **Location:** While Negri bodies are diagnostic, they are absent in about 20% of rabies cases; their absence does not rule out the disease. * **Rabies Virus Shape:** Bullet-shaped (Rhabdoviridae family). * **Transmission:** Retrograde axonal transport from the site of the bite to the CNS.

Q: Viral gastroenteritis may be caused by all of the following in infants and young children except?

Enterovirus. **Explanation:** The correct answer is **Enterovirus**. While the name "Enterovirus" suggests an intestinal origin, these viruses (such as Poliovirus, Coxsackievirus, and Echovirus) primarily replicate in the gastrointestinal tract but **do not typically cause gastroenteritis**. Instead, they cause systemic manifestations like meningitis, herpangina, hand-foot-mouth disease, and myocarditis. **Analysis of Options:** * **Enterovirus (Option A):** These are members of the Picornaviridae family. They enter via the fecal-oral route and replicate in the Peyer’s patches, but they are transient inhabitants of the gut and do not cause mucosal damage leading to diarrhea. * **Coronavirus (Option B):** Certain strains of Coronaviruses are recognized causes of pediatric viral diarrhea, though they are less common than Rotavirus. * **Calicivirus (Option C):** This family includes **Norovirus** and Sapovirus. Norovirus is the leading cause of gastroenteritis outbreaks across all age groups worldwide. * **Adenovirus (Option D):** Specifically, **serotypes 40 and 41** (Enteric Adenoviruses) are significant causes of prolonged watery diarrhea in infants and young children. **Clinical Pearls for NEET-PG:** * **Rotavirus:** The most common cause of severe infantile diarrhea worldwide (Reovirus family, double-stranded RNA, wheel-like appearance). * **Norovirus:** The most common cause of epidemic gastroenteritis (cruise ships, schools). * **Mechanism:** Viral gastroenteritis typically causes **osmotic diarrhea** due to the destruction of mature enterocytes at the tips of villi, leading to malabsorption. * **Management:** The cornerstone of treatment is **ORS** and Zinc supplementation; antibiotics are contraindicated.

Q: Both intranuclear and intracytoplasmic inclusions are present in which of the following viruses?

Measles virus. ### Explanation The presence of inclusion bodies is a hallmark of viral infections, representing sites of viral replication or accumulation of viral proteins. **1. Why Measles Virus is Correct:** Measles virus (a member of the *Paramyxoviridae* family) is unique because it produces **both intranuclear and intracytoplasmic inclusion bodies**. These are known as **Warthin-Finkeldey cells**, which are multinucleated giant cells containing these characteristic inclusions. This occurs because the virus replicates in the cytoplasm but its nucleocapsid proteins also accumulate within the nucleus. **2. Analysis of Incorrect Options:** * **Pox Virus:** These are large DNA viruses that replicate entirely in the cytoplasm. Therefore, they produce **only intracytoplasmic** inclusions (e.g., **Guarnieri bodies** in Smallpox or **Molluscum bodies** in Molluscum contagiosum). * **Hepatitis B Virus (HBV):** HBV is associated with "ground-glass hepatocyte" appearance due to HBsAg accumulation in the cytoplasm, but it does not typically present with the classic dual inclusion pattern described in the question. * **HIV:** As a retrovirus, HIV integrates into the host genome. While it causes syncytia formation in cell cultures, it is not characterized by the diagnostic dual inclusion bodies seen in Measles. **3. High-Yield Clinical Pearls for NEET-PG:** * **Dual Inclusions (Both):** Measles virus and Cytomegalovirus (CMV). *Note: CMV is famous for "Owl’s eye" intranuclear inclusions, but also has small cytoplasmic inclusions.* * **Intracytoplasmic Only:** Poxvirus (Guarnieri bodies), Rabies (Negri bodies), Reovirus. * **Intranuclear Only:** Herpes Simplex Virus (Cowdry Type A), Adenovirus (Cowdry Type B), Papovavirus. * **Measles Mnemonic:** Remember the **3 C's** (Cough, Coryza, Conjunctivitis) + **Koplik spots** (pathognomonic).

Q: What is true about HSV encephalitis?

All of the above. **Explanation:** Herpes Simplex Virus (HSV) encephalitis is the most common cause of sporadic fatal encephalitis worldwide. The correct answer is **D (All of the above)** based on the following clinical and pathological features: 1. **Causative Agent (Option A):** In adults and children beyond the neonatal period, HSV encephalitis is almost exclusively caused by **HSV-1** (usually due to reactivation of the virus in the trigeminal ganglion). In contrast, HSV-2 is more commonly associated with neonatal encephalitis and aseptic meningitis. 2. **Pathology (Option B):** A hallmark of HSV encephalitis is its predilection for the **temporal lobes**. It causes necrotizing, **hemorrhagic inflammation**, which can be visualized as hyperintensities on MRI (T2/FLAIR) and often leads to focal neurological deficits or seizures. 3. **Histology (Option C):** Microscopic examination of infected brain tissue reveals characteristic **Cowdry Type A inclusion bodies**. These are intranuclear, **eosinophilic** (acidophilic) droplets surrounded by a clear halo, representing viral replication sites. **High-Yield Clinical Pearls for NEET-PG:** * **Site Predilection:** Temporal lobes and orbital-frontal cortex (look for "temporal lobe involvement" in clinical vignettes). * **Diagnosis:** **CSF PCR** is the gold standard (highly sensitive and specific). * **EEG Findings:** Periodic lateralized epileptiform discharges (PLEDs). * **Treatment:** Immediate IV **Acyclovir** is the drug of choice; do not wait for PCR results if clinical suspicion is high. * **Clinical Sign:** Patients may present with sudden onset fever, headache, and psychiatric symptoms/personality changes (due to temporal lobe necrosis).

Q: What oncogenic risk is associated with HPV types 6 and 11?

Low. **Explanation:** Human Papillomavirus (HPV) is a double-stranded DNA virus with over 100 genotypes, classified based on their association with malignancy. **Why Option B is Correct:** HPV types **6 and 11** are classified as **low-risk types**. While they are highly infectious and cause significant morbidity, they rarely integrate their DNA into the host genome. Instead, they typically exist as episomes (extrachromosomal DNA), leading to benign epithelial proliferations rather than invasive squamous cell carcinoma. They are the primary causative agents of **Condyloma acuminata** (anogenital warts) and **Laryngeal Papillomatosis**. **Why Other Options are Incorrect:** * **Option A (High):** High-risk types include **HPV 16 and 18** (most common), along with 31 and 33. These types produce E6 and E7 oncoproteins that inhibit p53 and Rb tumor suppressor proteins, respectively, leading to cervical, anal, and oropharyngeal cancers. * **Option C (None):** While "low risk," these types are not "no risk." Rare cases of malignant transformation (e.g., Buschke-Löwenstein tumors) can occur, particularly in immunocompromised states. * **Option D (Variable):** HPV risk is consistently categorized by genotype; 6 and 11 are strictly defined in the low-risk category in clinical oncology. **High-Yield NEET-PG Pearls:** * **Laryngeal Papillomatosis:** HPV 6 and 11 are the most common cause of benign tumors of the larynx in children (acquired during birth). * **Vaccination:** The Quadrivalent (Gardasil) and Nonavalent vaccines cover types 6 and 11 to prevent genital warts. * **Koilocytes:** The hallmark cytological finding of HPV infection (shrunken "raisin-like" nucleus with a large perinuclear halo).

Question 1

Suckling mice are used for the isolation of which of the following viruses?

Accepted Answer

Coxsackie virus

Answer

Pox virus

Answer

Herpes virus

Answer

Adenovirus

Question 2

A 1-year-old child develops voluminous watery diarrhea and vomiting. Which of the following viruses is the most likely cause of the child's diarrhea?

Accepted Answer

Rotavirus

Answer

Coronavirus

Answer

Lymphocytic choriomeningitis virus

Answer

Norwalk agent

Question 3

Echoviruses are cytopathogenic human viruses that mainly infect which system?

Accepted Answer

Intestinal tract

Answer

Respiratory system

Answer

Central nervous system

Answer

Blood and lymphatic systems

Question 4

Negri bodies in brain are characteristically seen in which of the following conditions?

Accepted Answer

Rabies

Answer

Botulism

Answer

Chickenpox

Answer

Herpes encephalitis

Question 5

Which of the following is an oncogenic retrovirus?

Accepted Answer

HTLV-1

Answer

HPV

Answer

EBV

Answer

HBV

Question 6

Viral gastroenteritis may be caused by all of the following in infants and young children except?

Accepted Answer

Enterovirus

Answer

Coronavirus

Answer

Calicivirus

Answer

Adenovirus

Question 7

Which of the following statements is true about HIV?

Accepted Answer

Male-to-female transmission of HIV is higher than female-to-male transmission.

Answer

HIV is not transmitted through semen.

Answer

There are more chances of HIV transmission during LSCS than normal labor.

Answer

HIV is more infectious than hepatitis B.

Question 8

Both intranuclear and intracytoplasmic inclusions are present in which of the following viruses?

Accepted Answer

Measles virus

Answer

Pox Virus

Answer

Hepatitis B virus

Answer

HIV

Question 9

What is true about HSV encephalitis?

Accepted Answer

All of the above

Answer

Caused by HSV-1

Answer

Hemorrhagic lesion seen

Answer

Eosinophilic inclusion bodies seen

Question 10

What oncogenic risk is associated with HPV types 6 and 11?

Accepted Answer

Low

Answer

High

Answer

None

Answer

Variable

Virology — MCQs

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