Virology Practice Questions

Q: Which of the following is false regarding poliomyelitis?

Bilateral symmetrical paralysis. Poliomyelitis is an acute viral infection caused by the Poliovirus (an Enterovirus), which selectively destroys the **anterior horn cells** of the spinal cord. ### **Why Option B is the Correct Answer (False Statement)** The hallmark of paralytic polio is **asymmetrical** paralysis. The virus affects motor neurons in a random, patchy distribution. Therefore, it typically presents as **unilateral** involvement or involvement of different muscle groups on both sides with varying degrees of severity. Symmetrical paralysis is more characteristic of conditions like Guillain-Barré Syndrome (GBS). ### **Analysis of Other Options** * **A. Descending paralysis:** This is a characteristic feature of polio. The paralysis often starts proximally (e.g., hip/shoulder) and moves distally (e.g., feet/hands). * **C. Non-progressive paralysis:** Once the acute febrile phase ends and the temperature returns to normal, the paralysis does not progress further. This is known as "morning paralysis." * **D. Lower motor neuron (LMN) type:** Since the virus destroys the anterior horn cells (the final common pathway for motor signals), it results in LMN signs: flaccid paralysis, loss of deep tendon reflexes (areflexia), and muscle atrophy. ### **High-Yield Clinical Pearls for NEET-PG** * **Most common presentation:** Inapparent/Asymptomatic infection (>90% of cases). * **Specimen of choice:** Stool (virus is excreted for weeks). * **Post-Polio Syndrome:** Occurs decades after recovery due to the gradual failure of overworked remaining motor neurons. * **Differential Diagnosis:** Unlike Polio, **GBS** presents with *ascending*, *symmetrical* paralysis and *sensory* involvement. * **Vaccines:** Salk (IPV - Killed) and Sabin (OPV - Live attenuated). Sabin can rarely cause VAPP (Vaccine-Associated Paralytic Polio).

Q: Antemortem diagnosis of rabies is commonly made by?

Skin biopsy. **Explanation:** The antemortem diagnosis of rabies is challenging and requires high sensitivity. The **Skin Biopsy** (taken from the nuchal skin at the hairline) is considered the most reliable antemortem method. **1. Why Skin Biopsy is correct:** Rabies virus is highly neurotropic. After replicating in muscle cells, it travels via retrograde axonal transport to the CNS and subsequently spreads to highly innervated organs. The skin at the **nape of the neck** contains a high density of nerve plexuses surrounding hair follicles. A full-thickness skin biopsy allows for the detection of rabies antigen using **Direct Fluorescent Antibody (DFA)** testing or viral RNA via RT-PCR within these cutaneous nerves. **2. Analysis of Incorrect Options:** * **Corneal Scraping (A):** While historically used, it has low sensitivity and is technically difficult to perform without causing trauma. It is no longer the preferred method. * **Brain Biopsy (B):** This is the "Gold Standard" for diagnosis (looking for **Negri bodies**), but it is almost exclusively performed **post-mortem**. It is too invasive for routine antemortem diagnosis. * **Saliva (D):** Saliva can be used for RT-PCR or viral isolation, but viral shedding is intermittent. Therefore, a single negative saliva test cannot rule out rabies; multiple samples are required, making it less definitive than a skin biopsy. **High-Yield Pearls for NEET-PG:** * **Gold Standard (Post-mortem):** DFA on brain tissue (Hippocampus/Cerebellum). * **Pathognomonic sign:** Negri bodies (intracytoplasmic eosinophilic inclusions). * **Incubation period:** Usually 1–3 months (rarely 1 year). * **Hydrophobia:** Occurs due to forceful spasms of the diaphragm and accessory respiratory muscles when attempting to swallow.

Q: All of the following are clinical manifestations of Epstein Barr virus (EBV), EXCEPT:

Slow virus disease. **Explanation:** **1. Why "Slow virus disease" is the correct answer:** Slow virus diseases are characterized by a very long incubation period (months to years) and a progressive, usually fatal, clinical course. Classic examples include **Subacute Sclerosing Panencephalitis (SSPE)** caused by Measles, **Progressive Multifocal Leukoencephalopathy (PML)** caused by the JC virus, and Prion diseases (like Kuru or CJD). Epstein-Barr Virus (EBV), a member of the *Gammaherpesvirinae* subfamily, causes acute, latent, or neoplastic infections, but it is not classified as a "slow virus." **2. Analysis of incorrect options:** * **Infectious Mononucleosis (IM):** This is the most common acute clinical manifestation of EBV ("Glandular fever"). It presents with the classic triad of fever, pharyngitis, and lymphadenopathy, often accompanied by atypical lymphocytosis (Downey cells). * **Lymphoma:** EBV is highly oncogenic. It is strongly associated with **Burkitt lymphoma** (starry-sky appearance), Hodgkin lymphoma, and B-cell lymphomas in immunocompromised patients. * **Bell’s Palsy:** EBV is a recognized viral trigger for facial nerve paralysis (Bell’s palsy). It is often listed alongside HSV-1 and VZV as a potential causative agent for cranial nerve mononeuropathy. **3. NEET-PG High-Yield Pearls:** * **Receptor:** EBV binds to the **CD21** receptor (CR2) on B-cells and nasopharyngeal epithelial cells. * **Diagnosis:** The **Paul-Bunnell Test** (detecting heterophile antibodies) is the classic screening test. * **Other Malignancies:** EBV is also linked to **Nasopharyngeal Carcinoma** and Oral Hairy Leukoplakia (in HIV patients). * **Atypical Lymphocytes:** These are actually activated **T-cells (CD8+)** responding to the infected B-cells.

Q: Hepatitis B surface antigen in a patient's serum indicates that the patient is:

Potentially infectious. **Explanation:** The presence of **Hepatitis B surface antigen (HBsAg)** in a patient's serum is the hallmark of an active Hepatitis B virus (HBV) infection. It is the first serological marker to appear after infection (appearing before the onset of symptoms or elevation of ALT) and its presence signifies that the virus is actively replicating or present in the liver. Therefore, any individual who is HBsAg-positive must be considered **potentially infectious** via blood, semen, or other body fluids. **Analysis of Options:** * **Option A (Recovered):** Recovery is characterized by the disappearance of HBsAg and the appearance of **Anti-HBs** (protective antibodies). * **Option C (Acceptable blood donor):** Any person testing positive for HBsAg is permanently deferred from blood donation to prevent transfusion-transmitted HBV. * **Option D (Immune to exacerbations):** Persistence of HBsAg beyond 6 months indicates **chronic infection**. Chronic carriers are at risk for acute exacerbations (flares), cirrhosis, and hepatocellular carcinoma; they are not immune to the disease's progression. **NEET-PG High-Yield Pearls:** * **HBsAg:** The first marker to appear; if it persists >6 months, the patient is a chronic carrier. * **Anti-HBs:** Indicates immunity (either via recovery or vaccination). * **HBeAg:** An indicator of high viral replication and **high infectivity**. * **Window Period:** The interval where HBsAg disappears but Anti-HBs hasn't appeared yet. The only marker present is **Anti-HBc IgM**. * **Screening:** HBsAg is the primary tool for screening blood donors and pregnant women.

Q: Which of the following viruses does not produce viral esophagitis?

Adenovirus. **Explanation:** Viral esophagitis is a common opportunistic infection, primarily occurring in immunocompromised individuals (e.g., HIV/AIDS, transplant recipients, or those on chemotherapy). **Why Adenovirus is the correct answer:** While **Adenovirus** is a common cause of respiratory infections, conjunctivitis (pink eye), and hemorrhagic cystitis, it is **not** a recognized cause of viral esophagitis. It typically affects the respiratory and gastrointestinal tracts (causing diarrhea), but esophageal involvement is clinically negligible or non-existent. **Analysis of incorrect options:** * **Herpes Simplex Virus (HSV):** HSV-1 is the most common cause of viral esophagitis. It typically presents with "punched-out" ulcers and characteristic **Cowdry Type A** intranuclear inclusion bodies. * **Cytomegalovirus (CMV):** CMV is the second most common cause. Unlike HSV, it produces large, shallow, linear ulcerations. Histology shows "Owl’s eye" inclusion bodies (both intranuclear and intracytoplasmic). * **Varicella-Zoster Virus (VZV):** Though rarer than HSV or CMV, VZV can cause esophagitis, usually in children with chickenpox or immunocompromised adults with disseminated shingles. It presents with vesicular lesions similar to its cutaneous manifestation. **NEET-PG High-Yield Pearls:** 1. **HSV Esophagitis:** Multiple, small, deep ulcers. Biopsy shows multinucleated giant cells with Tzanck smear positivity. 2. **CMV Esophagitis:** Large, solitary, shallow/linear ulcers. It is a common AIDS-defining illness (CD4 < 50 cells/mm³). 3. **Treatment:** Acyclovir is the drug of choice for HSV/VZV; Ganciclovir is used for CMV. 4. **Candida albicans:** The most common overall cause of infectious esophagitis (presents with white plaques/pseudomembranes).

Q: Which marker is positive in a patient who is a supercarrier of Hepatitis B?

HBeAg. In Hepatitis B serology, the term **"Supercarrier"** refers to an individual who is not only chronically infected but also highly infectious to others. ### 1. Why HBeAg is the Correct Answer **HBeAg (Hepatitis B e-Antigen)** is the hallmark of **active viral replication**. When HBeAg is present in the blood, it indicates a high viral load and high infectivity. A "supercarrier" is defined by the presence of HBeAg, as these patients have a significantly higher risk of transmitting the virus via needle-stick injuries or vertical transmission (mother-to-child) compared to HBeAg-negative carriers. ### 2. Analysis of Incorrect Options * **HBsAg (Hepatitis B Surface Antigen):** While HBsAg is the first marker to appear and its persistence for >6 months defines a **chronic carrier**, it does not distinguish between low and high infectivity. All supercarriers are HBsAg positive, but not all HBsAg positive patients are supercarriers. * **Anti-HBc IgG:** This antibody indicates a past or chronic infection. It persists for life after exposure but does not correlate with the level of viral replication or infectivity. * **All of the above:** While a supercarrier will technically be positive for HBsAg and Anti-HBc IgG, **HBeAg** is the specific diagnostic marker that defines the "supercarrier" status (high infectivity state). ### 3. High-Yield Clinical Pearls for NEET-PG * **Best indicator of infectivity:** HBeAg (or HBV-DNA levels). * **First marker to appear:** HBsAg. * **Marker of "Window Period":** Anti-HBc IgM (HBsAg and Anti-HBs are both negative). * **Marker of Immunity:** Anti-HBs (indicates recovery or vaccination). * **Vertical Transmission:** If a mother is HBeAg positive, the risk of transmitting HBV to the newborn is ~90%.

Q: Negri bodies are characteristic inclusions found in neurons infected with the rabies virus. In which part of the central nervous system are they most commonly found?

Hippocampus. **Explanation:** **Negri bodies** are pathognomonic intracytoplasmic, eosinophilic inclusion bodies found in neurons infected by the **Rabies virus** (a Lyssavirus of the Rhabdoviridae family). These bodies represent sites of viral replication and consist of viral nucleocapsid proteins. 1. **Why Hippocampus is correct:** While the rabies virus spreads throughout the entire central nervous system (CNS), Negri bodies have a predilection for specific areas. They are most consistently and abundantly found in the **Pyramidal cells of the Hippocampus (Ammon’s horn)** and the **Purkinje cells of the Cerebellum**. Identification of these inclusions in these specific sites remains the gold standard for post-mortem histological diagnosis. 2. **Analysis of Incorrect Options:** * **Brain stem & Spinal cord:** Although the virus travels through the spinal cord and involves the brain stem (leading to cranial nerve dysfunction), Negri bodies are less frequently visualized here compared to the hippocampus. * **Cerebral cortex:** While cortical neurons can contain inclusions, they are not the "most common" or characteristic site used for diagnostic identification. **High-Yield Clinical Pearls for NEET-PG:** * **Morphology:** Negri bodies are sharply outlined, round or oval, and typically measure 1–7 µm. They are **intracytoplasmic** (unlike Herpes, which is intranuclear). * **Staining:** Best visualized using **Sellers’ stain** (basic fuchsin and methylene blue). * **Diagnosis:** The most sensitive and preferred diagnostic test for rabies in animals/humans is the **Direct Fluorescent Antibody (DFA)** test on brain tissue or skin biopsy (from the nape of the neck). * **Clinical Course:** Rabies is characterized by a long incubation period (1–3 months) because of slow retrograde axonal transport (8–20 mm/day) to the CNS.

Q: An immunocompromised person with a history of seizures had an MRI that revealed a temporal lobe lesion. Brain biopsy results showed multinucleated giant cells with intranuclear inclusions. What is the most probable cause of the lesion?

Cytomegalovirus infection. **Explanation:** The correct answer is **Cytomegalovirus (CMV) infection**. In immunocompromised patients (such as those with HIV/AIDS), CMV can cause encephalitis characterized by subacute dementia or focal neurological deficits. The histopathological hallmark of CMV is the presence of **multinucleated giant cells** and large, eosinophilic **intranuclear inclusions** (classically described as "Owl’s eye" appearance). While CMV typically causes periventricular calcifications in neonates, in adults, it can present with focal lesions in various brain regions, including the temporal lobe. **Why other options are incorrect:** * **Toxoplasmosis:** While common in immunocompromised patients, it typically presents as multiple ring-enhancing lesions on MRI. Histology shows tachyzoites and bradyzoites, not intranuclear inclusions. * **Herpes Simplex Encephalitis (HSE):** HSE is the most common cause of sporadic fatal encephalitis and classically involves the temporal lobe. However, it typically affects immunocompetent individuals and is characterized by Cowdry Type A inclusions. The presence of multinucleated giant cells in an immunocompromised setting more strongly points toward CMV or HIV-related pathology. * **Progressive Multifocal Leukoencephalopathy (PML):** Caused by the JC virus, it affects the white matter (demyelination). Histology shows enlarged oligodendrocytes with "ground-glass" nuclei, but not multinucleated giant cells. **NEET-PG High-Yield Pearls:** * **CMV:** "Owl’s eye" inclusions (Intranuclear + Intracytoplasmic). * **HSV:** Cowdry Type A inclusions (Intranuclear only). * **Rabies:** Negri bodies (Intracytoplasmic only). * **PML:** JC Virus; affects subcortical white matter; non-enhancing lesions. * **Temporal Lobe Involvement:** Always consider HSV-1 first in immunocompetent patients, but look for specific histopathological clues for CMV in the immunocompromised.

Q: The common cold is caused primarily by:

Viruses. **Explanation:** The common cold, or acute viral rhinosinusitis, is a self-limiting upper respiratory tract infection (URTI). **1. Why Viruses are Correct:** The vast majority (over 95%) of common colds are caused by viruses. The **Rhinovirus** (a Picornavirus) is the most frequent causative agent, accounting for 30–50% of cases. Other significant viral causes include Coronaviruses, Adenoviruses, Respiratory Syncytial Virus (RSV), and Parainfluenza viruses. These viruses infect the nasal epithelium, leading to inflammation, mucus hypersecretion, and the classic symptoms of rhinorrhea, sneezing, and sore throat. **2. Why Other Options are Incorrect:** * **Bacteria:** While bacteria like *Streptococcus pneumoniae* or *Haemophilus influenzae* can cause secondary infections (e.g., sinusitis or otitis media), they are not the primary cause of the common cold. Antibiotics are therefore ineffective for initial treatment. * **Fungi:** Fungal infections of the respiratory tract (like Aspergillosis or Mucormycosis) are rare and typically occur in immunocompromised individuals; they do not present as a standard "common cold." * **Allergy:** Allergic rhinitis can mimic cold symptoms (sneezing, watery eyes), but it is an IgE-mediated hypersensitivity reaction to environmental triggers (pollen, dust) rather than an infectious process. **NEET-PG High-Yield Pearls:** * **Most common cause:** Rhinovirus (binds to **ICAM-1** receptors). * **Seasonality:** Rhinoviruses peak in autumn/spring; Coronaviruses peak in winter. * **Adenovirus:** Often associated with "Pharyngoconjunctival fever" (sore throat + conjunctivitis). * **Treatment:** Purely symptomatic (decongestants, NSAIDs). Zinc gluconate may reduce duration if started within 24 hours.

Question 1

Which of the following is false regarding poliomyelitis?

Accepted Answer

Bilateral symmetrical paralysis

Answer

Descending paralysis

Answer

Non-progressive paralysis

Answer

Lower motor neuron type paralysis

Question 2

Antemortem diagnosis of rabies is commonly made by?

Accepted Answer

Skin biopsy

Answer

Corneal scraping

Answer

Brain biopsy

Answer

Saliva

Question 3

What is the relationship between viremia and the presence of rubella virus in the throat of infected persons, and the onset of the rash?

Accepted Answer

Viremia and rubella virus in the throat precede the rash by 5 to 7 days.

Answer

Viremia and rubella virus in the throat precede the rash by 1 to 2 days.

Answer

Viremia and rubella virus in the throat occur coincidentally with the rash.

Answer

Viremia and rubella virus in the throat occur 1 to 2 days after the rash.

Question 4

All of the following are clinical manifestations of Epstein Barr virus (EBV), EXCEPT:

Accepted Answer

Slow virus disease

Answer

Bell's palsy

Answer

Infectious mononucleosis

Answer

Lymphoma

Question 5

Hepatitis B surface antigen in a patient's serum indicates that the patient is:

Accepted Answer

Potentially infectious

Answer

Recovered

Answer

An acceptable blood donor

Answer

Immune to subsequent exacerbations of the disease

Question 6

Which of the following viruses does not produce viral esophagitis?

Accepted Answer

Adenovirus

Answer

Herpes simplex

Answer

Varicella

Answer

Cytomegalovirus

Question 7

Which marker is positive in a patient who is a supercarrier of Hepatitis B?

Accepted Answer

HBeAg

Answer

HBsAg

Answer

Anti-HBc IgG

Answer

All of the above

Question 8

Negri bodies are characteristic inclusions found in neurons infected with the rabies virus. In which part of the central nervous system are they most commonly found?

Accepted Answer

Hippocampus

Answer

Brain stem

Answer

Cerebral cortex neurons

Answer

Spinal cord

Question 9

An immunocompromised person with a history of seizures had an MRI that revealed a temporal lobe lesion. Brain biopsy results showed multinucleated giant cells with intranuclear inclusions. What is the most probable cause of the lesion?

Accepted Answer

Cytomegalovirus infection

Answer

Toxoplasmosis

Answer

Herpes simplex encephalitis

Answer

Progressive multifocal leukoencephalopathy

Question 10

The common cold is caused primarily by:

Accepted Answer

Viruses

Answer

Bacteria

Answer

Fungi

Answer

Allergy

Virology — MCQs

Virology — MCQs

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