Virology — MCQs

Virology Indian Medical PG Practice Questions and MCQs

Question 401: Intracytoplasmic inclusion bodies are diagnostic of which viral infection?

A. Rabies (Correct Answer)
B. Measles
C. Adenovirus
D. Mumps

Explanation: **Explanation:** The presence of **intracytoplasmic inclusion bodies** is a hallmark of several viral infections, but it is classically diagnostic for **Rabies**. These specific inclusions are known as **Negri bodies**. They are eosinophilic, sharply outlined, round or oval inclusions found most commonly in the Purkinje cells of the cerebellum and the pyramidal cells of the hippocampus. Their presence is pathognomonic for Rabies, as they represent sites of viral replication (nucleocapsid accumulation). **Analysis of Options:** * **B. Measles:** This virus is unique because it produces **both** intracytoplasmic and intranuclear inclusion bodies (Warthin-Finkeldey cells). Since the question asks specifically for intracytoplasmic diagnostic inclusions, Rabies is the more specific answer. * **C. Adenovirus:** This DNA virus replicates in the nucleus, producing **intranuclear** inclusion bodies (e.g., "smudge cells"). * **D. Mumps:** While it is a cytoplasmic virus, it does not typically produce distinct, diagnostic inclusion bodies used for routine histopathological diagnosis. **High-Yield Clinical Pearls for NEET-PG:** * **Intranuclear Inclusions:** * *Cowdry Type A:* Herpes Simplex Virus (HSV), Varicella-Zoster Virus (VZV), and Yellow Fever (Torres bodies). * *Cowdry Type B:* Poliovirus. * *Owl’s Eye appearance:* Cytomegalovirus (CMV). * **Intracytoplasmic Inclusions:** * *Negri bodies:* Rabies. * *Guarnieri bodies:* Variola (Smallpox) and Vaccinia. * *Bollinger bodies:* Fowlpox. * *Molluscum bodies (Henderson-Patterson):* Molluscum contagiosum. * **Both (Intranuclear + Intracytoplasmic):** Measles and CMV (though CMV is primarily known for its large intranuclear "owl's eye").

Question 402: What are the most common viruses isolated from herpangina?

A. Coxsackievirus A (Correct Answer)
B. Coxsackievirus B
C. Echoviruses
D. Enterovirus 71

Explanation: **Explanation:** **Herpangina** is a common pediatric infection characterized by sudden onset fever, sore throat, and distinctive vesicular-ulcerative lesions on the posterior oropharynx (tonsillar pillars, soft palate, and uvula). **Why Coxsackievirus A is correct:** The primary causative agents of herpangina are **Group A Coxsackieviruses** (specifically serotypes A1–10, A16, and A22). These belong to the *Enterovirus* genus of the *Picornaviridae* family. Coxsackievirus A is also the most common cause of Hand-Foot-and-Mouth Disease (HFMD), particularly serotype A16. **Analysis of Incorrect Options:** * **Coxsackievirus B:** These are more commonly associated with pleurodynia (Bornholm disease), myocarditis, pericarditis, and pancreatitis. * **Echoviruses:** While they can cause non-specific febrile illnesses and aseptic meningitis, they are infrequent causes of herpangina. * **Enterovirus 71:** Although EV-71 can cause herpangina and HFMD, it is less common than Coxsackie A and is clinically significant primarily because it is associated with severe neurological complications like brainstem encephalitis. **High-Yield Clinical Pearls for NEET-PG:** * **Site of Lesions:** Herpangina affects the **posterior** pharynx, whereas Herpetic Gingivostomatitis (HSV-1) typically affects the **anterior** mouth and gums. * **Seasonality:** Peak incidence occurs during **summer and autumn** months. * **Transmission:** Fecal-oral route is the primary mode of spread. * **Management:** Treatment is purely supportive (hydration and analgesics) as the condition is self-limiting.

Question 403: Measles is caused by a

A. Single stranded RNA enveloped virus (Correct Answer)
B. Single stranded RNA non-enveloped virus
C. Double stranded RNA enveloped virus
D. Double stranded RNA non-enveloped virus

Explanation: **Explanation:** Measles virus belongs to the **Genus Morbillivirus** within the **Family Paramyxoviridae**. Understanding its structural classification is fundamental for NEET-PG. 1. **Why Option A is Correct:** The Measles virus is a **pleomorphic, enveloped virus** containing a **single-stranded, negative-sense, non-segmented RNA** genome. The envelope is derived from the host cell plasma membrane and contains two critical glycoprotein spikes: the **Hemagglutinin (H)** protein (for attachment) and the **Fusion (F)** protein (for cell entry and syncytia formation). Notably, unlike other Paramyxoviruses, Measles lacks Neuraminidase activity. 2. **Why Other Options are Incorrect:** * **Option B:** Non-enveloped RNA viruses include Picornaviruses (like Polio) or Caliciviruses. Measles requires its lipid envelope for infectivity; detergents or heat easily inactivate it. * **Options C & D:** Double-stranded RNA (dsRNA) is characteristic of the **Reoviridae** family (e.g., Rotavirus). Most human pathogenic RNA viruses, including all Paramyxoviruses, are single-stranded. **High-Yield Clinical Pearls for NEET-PG:** * **Koplik’s Spots:** Pathognomonic bluish-white spots on an erythematous base found on the buccal mucosa opposite the lower second molars (precedes the rash). * **Vitamin A:** Supplementation is recommended by the WHO to reduce morbidity and mortality in children with Measles. * **Complications:** The most common complication is **Otitis Media**; the most common cause of death is **Pneumonia** (Hecht’s giant cell pneumonia). * **SSPE:** Subacute Sclerosing Panencephalitis is a rare, fatal, late complication occurring years after the initial infection due to a persistent defective virus in the CNS. * **Vaccine:** Live attenuated (Edmonston-Zagreb strain) administered at 9 months and 16-24 months.

Question 404: Which of the following statements is NOT true about viral envelopes?

A. The lipid bilayer is derived from host cell membranes.
B. The viral proteins embedded within the envelope are encoded by the virus itself.
C. The envelope is susceptible to dissolution by organic solvents like ether.
D. The envelope is essential for viral propagation in the next generation. (Correct Answer)

Explanation: **Explanation:** The correct answer is **D**. This statement is incorrect because not all viruses possess an envelope. Viruses are broadly classified into **enveloped** and **non-enveloped (naked)** viruses. While an envelope is crucial for the infectivity of enveloped viruses (e.g., HIV, Influenza), naked viruses (e.g., Poliovirus, Hepatitis A) propagate successfully without one. In fact, naked viruses are often more stable in the environment. **Analysis of Options:** * **Option A:** True. The viral envelope is a lipid bilayer acquired during the process of "budding" from host cell membranes (plasma membrane, nuclear membrane, or ER/Golgi). * **Option B:** True. While the lipids are host-derived, the glycoproteins (spikes) embedded in the envelope are encoded by the **viral genome**. these are essential for attachment to host receptors. * **Option C:** True. Because the envelope is composed of lipids, it is highly sensitive to **organic solvents** (ether, chloroform), detergents, and bile salts. This is why enveloped viruses are usually transmitted via direct contact or droplets rather than the feco-oral route. **High-Yield NEET-PG Pearls:** * **Stability:** Naked viruses are resistant to heat, acids, and detergents; enveloped viruses are fragile and easily inactivated. * **Disinfection:** Ether sensitivity is a classic laboratory test to differentiate enveloped from non-enveloped viruses. * **Exceptions:** Most DNA viruses are naked (except Herpes, Hepadna, Pox); most RNA viruses are enveloped (except Reo, Picorna, Calici, Hepe). * **Clinical Link:** Alcohol-based sanitizers work effectively against enveloped viruses (like SARS-CoV-2) by dissolving the lipid envelope.

Question 405: Which of the following are arboviral diseases?

A. Japanese encephalitis, Dengue
B. Japanese encephalitis, Dengue, Yellow fever (Correct Answer)
C. Japanese encephalitis, Yellow fever
D. Dengue, Yellow fever

Explanation: **Explanation** **1. Understanding the Concept (Why B is correct):** Arboviruses (Arthropod-borne viruses) are a functional group of viruses transmitted to humans through the bites of infected arthropods, primarily mosquitoes and ticks. * **Japanese Encephalitis (JE):** Transmitted by the *Culex tritaeniorhynchus* mosquito. It is the leading cause of viral encephalitis in Asia. * **Dengue:** Transmitted by the *Aedes aegypti* mosquito. It is a member of the Flaviviridae family. * **Yellow Fever:** Also transmitted by the *Aedes aegypti* mosquito. It is characterized by jaundice and hemorrhagic manifestations. Since all three diseases listed in Option B are transmitted via arthropod vectors, it is the most comprehensive and correct choice. **2. Analysis of Incorrect Options:** * **Options A, C, and D:** While the diseases listed in these options are indeed arboviral, they are **incomplete**. In NEET-PG, when multiple options contain correct facts, the "most complete" answer is the correct one. Option B encompasses all the major arboviruses mentioned across the other choices. **3. High-Yield Clinical Pearls for NEET-PG:** * **Flaviviridae Family:** All three (JE, Dengue, Yellow Fever) belong to the *Flaviviridae* family and contain ssRNA. * **Vector Specificity:** Remember "C" for *Culex* and "C" for Rice fields (JE); "A" for *Aedes* and "A" for Urban areas (Dengue/Yellow Fever). * **KFD (Kyasanur Forest Disease):** A high-yield Indian arbovirus transmitted by **ticks** (*Haemaphysalis spinigera*). * **Non-Arboviruses:** Note that diseases like Malaria and Kala-azar are arthropod-borne but are **protozoal**, not viral. Similarly, Rabies is viral but **not** arboviral (transmitted via animal bites).

Question 406: Which immunoassay is performed in HIV to detect the presence of antibodies to individual viral proteins?

A. NASBA
B. ELISA
C. Western Blot (Correct Answer)
D. PCR

Explanation: ### Explanation **Correct Answer: C. Western Blot** The **Western Blot** is a protein-based immunoassay used to detect specific antibodies against individual viral proteins. In the context of HIV, the virus is first dissociated into its component proteins (antigens), which are separated by molecular weight using gel electrophoresis and transferred to a membrane. When the patient's serum is added, antibodies bind to specific viral bands such as **gp120/160, gp41 (envelope), p24 (capsid), and p31 (polymerase)**. According to WHO/CDC criteria, a Western Blot is considered positive if antibodies against at least two of the three main gene products (Env, Gag, and Pol) are present. **Why the other options are incorrect:** * **ELISA (Option B):** While ELISA is the standard screening test for HIV, it detects the *total* presence of antibodies (or p24 antigen in 4th gen) in a pooled format. It does not differentiate between antibodies to individual viral proteins. * **PCR (Option D):** Polymerase Chain Reaction is a molecular technique used to detect viral **DNA or RNA** (nucleic acids), not antibodies. It is used for early diagnosis in newborns or for monitoring viral load. * **NASBA (Option A):** Nucleic Acid Sequence-Based Amplification is an isothermal amplification method used specifically to quantify **HIV-1 RNA** levels (viral load), not for antibody detection. **High-Yield Clinical Pearls for NEET-PG:** * **Screening vs. Confirmatory:** ELISA is the screening test (High Sensitivity); Western Blot was traditionally the confirmatory test (High Specificity). * **Window Period:** The time between infection and the appearance of detectable antibodies. 4th Generation ELISA (p24 Ag + Ab) has shortened this period significantly. * **Diagnosis in Infants:** HIV DNA PCR is the gold standard for diagnosing HIV in infants <18 months, as maternal IgG antibodies can cross the placenta and cause false positives in antibody tests. * **Indeterminate Result:** If a Western Blot shows some bands but does not meet the full criteria, it is labeled "indeterminate," often requiring a repeat test in 4-6 weeks.

Question 407: Class II exposure in animal bites includes which of the following?

A. Scratches without oozing of blood (Correct Answer)
B. Licks on a fresh wound
C. Scratch with oozing of blood on palm
D. Bites from wild animals

Explanation: The WHO and National Guidelines for Rabies Prophylaxis categorize animal exposures into three classes to determine the necessary Post-Exposure Prophylaxis (PEP). ### **Explanation of the Correct Option** **Option A (Scratches without oozing of blood)** is the correct answer because **Category II** exposure is defined as minor transdermal scratches or abrasions without bleeding, or nibbling of uncovered skin. These require immediate local wound treatment and the administration of the Rabies vaccine (ARV), but generally do not require Rabies Immunoglobulin (RIG). ### **Analysis of Incorrect Options** * **Option B (Licks on a fresh wound):** This is **Category III**. Any lick on broken skin (fresh wound) or mucous membranes allows the virus direct access to neural tissue, necessitating both ARV and RIG. * **Option C (Scratch with oozing of blood):** Any scratch or bite that causes **bleeding** (transdermal) is automatically classified as **Category III**, requiring full PEP (Vaccine + RIG). * **Option D (Bites from wild animals):** According to Indian guidelines, all bites by wild animals are high-risk and are treated as **Category III** regardless of the severity of the wound. ### **High-Yield Clinical Pearls for NEET-PG** * **Category I:** Touching/feeding animals, licks on **intact** skin. (Action: None, if history is reliable). * **Category II:** Minor scratches, no bleeding. (Action: Vaccine only). * **Category III:** Single/multiple transdermal bites, scratches with blood, licks on broken skin, or contact with bats. (Action: Vaccine + RIG). * **Site of RIG:** RIG should be infiltrated **in and around the wound**. Any remaining volume is injected IM at a site distant from the vaccine. * **Wound Care:** Immediate flushing with soap and water for 15 minutes is the most effective first-step in reducing viral load. Avoid suturing wounds; if necessary, do so only after RIG infiltration.

Question 408: When compared to the Western blot technique, the ELISA test is:

A. Less sensitive, less specific
B. More sensitive, more specific
C. Less sensitive, more specific
D. More sensitive, less specific (Correct Answer)

Explanation: ### Explanation In clinical virology, diagnostic testing often follows a two-tier approach: a **Screening Test** followed by a **Confirmatory Test**. **1. Why Option D is Correct:** * **ELISA (Enzyme-Linked Immunosorbent Assay)** is designed as a **screening test**. Screening tests prioritize **Sensitivity** (the ability to correctly identify those with the disease). High sensitivity ensures a "high catch rate," minimizing false negatives. However, this often comes at the cost of **Specificity**, leading to occasional false positives due to cross-reacting antibodies. * **Western Blot** is a **confirmatory test**. It prioritizes **Specificity** (the ability to correctly identify those without the disease) by detecting antibodies against multiple specific viral proteins (e.g., gp120, gp41, and p24 in HIV). This ensures that a positive result is truly positive, minimizing false positives. Therefore, compared to Western Blot, ELISA is **more sensitive** (better at screening) but **less specific** (more prone to false positives). **2. Why Other Options are Wrong:** * **A & C:** ELISA is highly sensitive; labeling it "less sensitive" is incorrect as it would fail its primary purpose as a screening tool. * **B:** If ELISA were more specific than Western Blot, there would be no need for the Western Blot as a confirmatory step. --- ### High-Yield Clinical Pearls for NEET-PG * **HIV Testing Strategy:** The current WHO/NACO guidelines have shifted towards using three different ERS (ELISA/Rapid/Simple) tests for diagnosis, but the classic "Screen with ELISA, Confirm with Western Blot" remains a fundamental concept for exams. * **Window Period:** Both tests can be negative during the window period. The earliest marker to appear in HIV is **p24 antigen** (detected by 4th Gen ELISA) or **HIV-RNA** (by PCR). * **Sensitivity vs. Specificity Mnemonic:** * **S**e**N**sitivty rules **OUT** (SNOUT) – used for screening. * **S**p**P**ecificity rules **IN** (SPIN) – used for confirmation.

Question 409: All of the following are true regarding influenza, except?

A. Point mutations in the hemagglutinin gene cause antigenic drift.
B. Acquisition of a completely new hemagglutinin gene causes antigenic shift.
C. Amantadine is active against influenza B only. (Correct Answer)
D. Amantadine shortens the illness.

Explanation: ### Explanation The correct answer is **C (Amantadine is active against influenza B only)** because this statement is factually incorrect. Amantadine and Rimantadine are M2 ion channel inhibitors that are active **only against Influenza A**. They are ineffective against Influenza B because Influenza B viruses lack the M2 protein target. #### Analysis of Options: * **Option A (Antigenic Drift):** This is a **true** statement. Antigenic drift refers to minor changes caused by point mutations in the genes coding for Hemagglutinin (HA) and Neuraminidase (NA). This occurs in both Influenza A and B and is responsible for seasonal epidemics. * **Option B (Antigenic Shift):** This is a **true** statement. Antigenic shift is a major change involving the acquisition of a completely new HA or NA gene through genetic reassortment (usually between human and animal/avian strains). This occurs **only in Influenza A** and leads to pandemics. * **Option D (Shortening illness):** This is a **true** statement. When administered within 48 hours of symptom onset, M2 inhibitors (and Neuraminidase inhibitors) can reduce the duration of fever and systemic symptoms by approximately 1–2 days. #### NEET-PG High-Yield Clinical Pearls: * **Drug Targets:** * **M2 Inhibitors (Amantadine/Rimantadine):** Target M2 protein; active against Influenza A only. (Note: High resistance rates currently limit their clinical use). * **Neuraminidase Inhibitors (Oseltamivir/Zanamivir):** Target NA; active against **both** Influenza A and B. * **Cap-dependent Endonuclease Inhibitor (Baloxavir):** Newer drug active against both A and B. * **Segmentation:** The Influenza genome is **segmented** (8 segments in A and B; 7 in C). This segmentation is the prerequisite for genetic reassortment (Antigenic Shift). * **Reye’s Syndrome:** Avoid Aspirin in children with Influenza due to the risk of fulminant hepatic failure and encephalopathy.

Question 410: All the following hepatitis viruses are transmitted by the parenteral route except?

A. Hepatitis B virus
B. Hepatitis C virus
C. Hepatitis D virus
D. Hepatitis E virus (Correct Answer)

Explanation: ### Explanation The transmission of hepatitis viruses is a high-yield topic for NEET-PG, categorized primarily into two routes: **Enteric** (fecal-oral) and **Parenteral** (blood-borne/sexual). **1. Why Hepatitis E is the Correct Answer:** Hepatitis E virus (HEV), along with Hepatitis A virus (HAV), is transmitted via the **fecal-oral route**, typically through contaminated water or food. It is not primarily transmitted through blood or parenteral routes. A key clinical distinction for HEV is its high mortality rate (up to 20%) in **pregnant women** due to fulminant hepatic failure. **2. Analysis of Incorrect Options (Parenteral Viruses):** * **Hepatitis B (HBV):** Transmitted via blood, sexual contact, and vertically (mother to child). It is a DNA virus and the most common cause of chronic hepatitis worldwide. * **Hepatitis C (HCV):** Primarily transmitted through blood (IV drug use, transfusions). It has the highest rate of progression to **chronicity** (approx. 80%). * **Hepatitis D (HDV):** A defective RNA virus that requires the HBsAg coat of HBV to replicate. It is transmitted parenterally either as a co-infection or super-infection with HBV. **3. NEET-PG Clinical Pearls:** * **Vowels go with the Bowels:** Hepatitis **A** and **E** are transmitted via the fecal-oral route. * **Consonants are Blood-borne:** Hepatitis **B, C, and D** are transmitted parenterally. * **HEV Genotypes:** Genotypes 1 and 2 are associated with waterborne epidemics in humans; Genotypes 3 and 4 are zoonotic (pork consumption). * **Incubation Period:** HEV has an average incubation period of 2–9 weeks.

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