Virology — MCQs

Virology Indian Medical PG Practice Questions and MCQs

Question 991: What is the most common presentation of congenital Cytomegalovirus (CMV) infection?

A. Hepatosplenomegaly (Correct Answer)
B. Microcephaly
C. Cerebral calcification
D. Chorioretinitis

Explanation: **Explanation:** Congenital Cytomegalovirus (CMV) is the most common intrauterine infection worldwide. While approximately 90% of affected neonates are asymptomatic at birth, among those who are **symptomatic**, **Hepatosplenomegaly** is the most frequent clinical finding (occurring in approximately 60-80% of cases). **Why Hepatosplenomegaly is correct:** CMV has a tropism for the reticuloendothelial system. In utero, the virus causes extramedullary hematopoiesis and inflammatory infiltration of the liver and spleen, leading to enlargement. It is often accompanied by jaundice and petechiae (blueberry muffin rash). **Analysis of Incorrect Options:** * **B. Microcephaly:** While a classic feature of the "TORCH" spectrum and a significant marker of poor neurodevelopmental prognosis, it occurs less frequently (approx. 40-50%) than visceral enlargement. * **C. Cerebral calcification:** In CMV, these are typically **periventricular** in distribution. While highly characteristic and a favorite for radiology-based questions, they are present in only about 30-40% of symptomatic cases. * **D. Chorioretinitis:** This is a common late manifestation or a finding in severe cases (approx. 10-20%), but it is significantly less common than hepatosplenomegaly or jaundice. **High-Yield Clinical Pearls for NEET-PG:** * **Most common overall presentation:** Asymptomatic (90%). * **Most common symptomatic presentation:** Hepatosplenomegaly. * **Most common long-term sequela:** Sensorineural Hearing Loss (SNHL)—CMV is the leading non-genetic cause of SNHL in children. * **Radiology Key:** Look for **Periventricular calcifications** (distinguish from Toxoplasmosis, which shows diffuse/scattered calcifications). * **Diagnosis:** Gold standard is **Viral culture or PCR of saliva/urine** within the first 3 weeks of life.

Question 992: Rabies encephalitis presents with all of the following clinical features except?

A. Tonic spasm of body
B. Sound phobia
C. Hypersalivation
D. Hypotonic paralysis (Correct Answer)

Explanation: **Explanation:** Rabies is a fatal viral encephalitis caused by the Lyssavirus (Rhabdoviridae family). The clinical presentation typically follows two patterns: **Encephalitic (Furious) Rabies** (80%) and **Paralytic (Dumb) Rabies** (20%). **Why Option D is the Correct Answer:** In the classic **Encephalitic (Furious) Rabies** described in the question, the hallmark is **hyper-excitability** and **spasticity**, not hypotonia. While Paralytic Rabies exists, it presents as an ascending symmetrical paralysis (resembling Guillain-Barré Syndrome). However, in the context of "Rabies Encephalitis" symptoms like spasms and phobias, **Hypotonic paralysis** is the "except" because the disease is characterized by intense muscle spasms and autonomic hyperactivity. **Analysis of Incorrect Options:** * **A. Tonic spasm of body:** Irritation of the motor neurons leads to generalized tonic-clonic spasms, often triggered by sensory stimuli (light, sound, or touch). * **B. Sound phobia:** Patients experience extreme "sensory hyperesthesia." Loud noises (Aerophobia/Akoustophobia) can trigger violent spasms of the diaphragm and accessory respiratory muscles. * **C. Hypersalivation:** Rabies causes autonomic dysfunction and excessive lacrimation/salivation. Combined with **hydrophobia** (spasms of deglutition muscles when seeing water), this leads to the classic "foaming at the mouth." **NEET-PG High-Yield Pearls:** * **Pathognomonic Sign:** **Negri Bodies** (intracytoplasmic eosinophilic inclusions) found most commonly in **Hippocampus** (Pyramidal cells) and **Cerebellum** (Purkinje cells). * **Mechanism:** The virus binds to **Nicotinic Acetylcholine Receptors** at the neuromuscular junction. * **Incubation Period:** Usually 1–3 months; depends on the distance of the bite from the CNS. * **Prophylaxis:** Category III bites (transdermal) require both **Rabies Vaccine** and **Rabies Immunoglobulin (RIG)**.

Question 993: A patient diagnosed with influenza reported onset of symptoms 18 hours ago. Which of the following is the most appropriate treatment for this patient?

A. Amantadine
B. Foscarnet
C. Oseltamivir (Correct Answer)
D. Ribavirin

Explanation: ### **Explanation** **Correct Answer: C. Oseltamivir** **Mechanism & Rationale:** Oseltamivir is a **Neuraminidase Inhibitor** effective against both Influenza A and B. Neuraminidase is an enzyme essential for the release of newly formed virions from infected host cells; by inhibiting it, the drug prevents the spread of the virus within the respiratory tract. The clinical efficacy of neuraminidase inhibitors is highly time-dependent. They are most effective when initiated within **48 hours** of symptom onset. Since this patient presented at 18 hours, Oseltamivir is the treatment of choice to reduce the duration and severity of symptoms. **Analysis of Incorrect Options:** * **A. Amantadine:** This is an M2 ion channel blocker that prevents viral uncoating. It is only active against Influenza A. However, it is no longer recommended for routine use due to widespread high-level resistance (nearly 100%) among circulating strains. * **B. Foscarnet:** This is a pyrophosphate analog used primarily for CMV retinitis or acyclovir-resistant HSV/VZV infections. It has no role in treating influenza. * **C. Ribavirin:** While it has broad-spectrum antiviral activity, it is primarily used for Chronic Hepatitis C (in combination) and severe RSV infections. It is not a first-line treatment for influenza. **High-Yield Clinical Pearls for NEET-PG:** * **Route of Administration:** Oseltamivir is oral; **Zanamivir** is inhaled (contraindicated in asthma/COPD); **Peramivir** is intravenous. * **Baloxavir Marboxil:** A newer single-dose drug that inhibits the "cap-snatching" endonuclease activity of the viral RNA polymerase. * **Chemoprophylaxis:** Oseltamivir can be used for post-exposure prophylaxis in high-risk individuals. * **Antigenic Drift vs. Shift:** Drift (point mutations) causes seasonal epidemics; Shift (reassortment) causes pandemics.

Question 994: What is the most common defect occurring in congenital rubella syndrome?

A. Cataract (Correct Answer)
B. Deafness
C. Microcephaly
D. Blindness

Explanation: **Explanation:** Congenital Rubella Syndrome (CRS) occurs due to transplacental transmission of the Rubella virus, primarily during the first trimester. While **Sensorineural Hearing Loss (SNHL)** is technically the most common *overall* manifestation of CRS (often appearing later), **Cataract** is classically cited as the most common and characteristic **major structural defect** identified at birth. **Why Cataract is the Correct Answer:** In the context of medical examinations like NEET-PG, the "Gregg’s Triad" is the gold standard for CRS: 1. **Eye defects:** Cataract (most common eye finding), glaucoma, or microphthalmia. 2. **Ear defects:** Sensorineural deafness. 3. **Heart defects:** Patent Ductus Arteriosus (PDA) or Peripheral Pulmonary Artery Stenosis. Cataracts in CRS are typically bilateral and have a "pearly white" appearance. **Analysis of Incorrect Options:** * **B. Deafness:** While SNHL is the most frequent *finding* in children with CRS (occurring in ~80%), it is often not detected immediately at birth. In many standardized formats, Cataract is prioritized as the hallmark congenital malformation. * **C. Microcephaly:** This occurs in CRS but is more characteristically associated with Congenital CMV infection or Zika virus. * **D. Blindness:** Blindness is a potential *outcome* of untreated cataracts or retinopathy (salt-and-pepper retinopathy), but it is not the primary defect itself. **High-Yield Clinical Pearls for NEET-PG:** * **Classic Triad:** Cataract + Deafness + PDA. * **Skin Manifestation:** "Blueberry muffin" spots (extramedullary hematopoiesis). * **Diagnosis:** Detection of Rubella-specific IgM in the newborn or persistence of IgG beyond 6 months. * **Vaccination:** Live attenuated **RA 27/3 strain** is used. It must be avoided in pregnancy.

Question 995: What is the most sensitive test for HIV infection?

A. Western blot
B. ELISA (Correct Answer)
C. Agglutination test
D. Complement fixation test (CFT)

Explanation: **Explanation:** The diagnosis of HIV infection primarily relies on the detection of antibodies and antigens. In clinical practice, **ELISA (Enzyme-Linked Immunosorbent Assay)** is the preferred screening test because it is designed for maximum **sensitivity**. 1. **Why ELISA is correct:** Modern 4th-generation ELISA kits detect both the **p24 antigen** and **anti-HIV antibodies (IgG/IgM)**. This dual detection significantly narrows the "window period," allowing for early diagnosis. Because it is highly sensitive, it ensures that very few true-positive cases are missed, making it the gold standard for screening blood donors and patients. 2. **Why other options are incorrect:** * **Western Blot:** While historically used as the "Gold Standard" for confirmation due to its high **specificity**, it is less sensitive than modern ELISAs and is technically demanding. Note: Current WHO/NACO guidelines have largely replaced Western Blot with rapid tests or supplemental ELISAs for confirmation. * **Agglutination Test:** These are rapid tests used for screening in field settings. While quick, they generally lack the standardized sensitivity of a laboratory ELISA. * **Complement Fixation Test (CFT):** This is an older serological method rarely used for HIV diagnosis due to low sensitivity and complexity compared to modern enzyme-based assays. **High-Yield Clinical Pearls for NEET-PG:** * **Screening Test:** ELISA (Highest Sensitivity). * **Confirmatory Test:** Western Blot (Highest Specificity - traditional); however, NACO uses a strategy of three different ELISA/Rapid tests. * **Early Diagnosis (Window Period):** **p24 antigen** (detected by ELISA) or **HIV-RNA PCR** (the earliest detectable marker, appearing ~10 days post-infection). * **Monitoring Treatment:** Viral load (Quantitative RT-PCR) is used to monitor HAART efficacy. * **Diagnosis in Infants (<18 months):** DNA-PCR is the test of choice (maternal antibodies persist in the infant, making ELISA unreliable).

Question 996: Transmission of cholera is primarily through which route?

A. Contaminated food with fecal matter
B. Contaminated water with fecal matter
C. Contaminated food with vomitus from an infected individual
D. All of the above (Correct Answer)

Explanation: **Explanation:** Cholera, caused by the bacterium *Vibrio cholerae*, is a classic example of a disease transmitted via the **fecal-oral route**. While contaminated water is the most common vehicle for large-scale outbreaks, the transmission dynamics are broader, involving any medium contaminated with the pathogen. 1. **Why "All of the above" is correct:** *Vibrio cholerae* is shed in massive quantities (up to $10^{12}$ organisms per liter) in the "rice-water" stools and vomitus of infected patients. * **Contaminated Water (Option B):** This is the primary reservoir. In areas with poor sanitation, feces enter the water supply, leading to explosive epidemics. * **Contaminated Food (Option A):** Food can be contaminated via "fingers, flies, and fluids." Vegetables grown with sewage water or shellfish harvested from contaminated estuaries are common sources. * **Vomitus (Option C):** A high-yield fact often overlooked is that the **vomitus** of a cholera patient is also infectious. If vomitus contaminates food or surfaces handled by others, it can transmit the disease. 2. **Clinical Pearls for NEET-PG:** * **Infective Dose:** High ($10^8$–$10^{11}$ cells) because the organism is acid-sensitive and must survive the gastric acid barrier. * **Haldane’s Rule:** Cholera is more severe in individuals with **Blood Group O**. * **Stool Characteristics:** Non-offensive, "rice-water" appearance with mucus flakes; contains high concentrations of Potassium and Bicarbonate. * **Gold Standard Diagnosis:** Stool culture on **TCBS (Thiosulfate Citrate Bile Salts Sucrose) agar**, where it forms yellow colonies. * **Treatment Priority:** Aggressive rehydration (ORS/IV fluids) is the mainstay; Doxycycline is the drug of choice to reduce the duration of shedding.

Question 997: What is the most sensitive test for the diagnosis of infectious mononucleosis?

A. Monospot test (Correct Answer)
B. Paul-Bunnel test
C. Lymphocytosis in peripheral smear
D. Culture

Explanation: **Explanation:** Infectious Mononucleosis (IM), primarily caused by **Epstein-Barr Virus (EBV)**, is characterized by the production of **heterophile antibodies**. These are IgM antibodies that agglutinate red blood cells of other species (sheep, horse, or bovine). **Why Option A is correct:** The **Monospot test** (a rapid latex agglutination test) is the most sensitive screening test for IM. it uses horse erythrocytes and is more sensitive and faster than the traditional Paul-Bunnell test. It becomes positive within the first 1-2 weeks of illness and has a sensitivity of approximately 85-90%. **Why other options are incorrect:** * **B. Paul-Bunnell test:** This is the classic tube agglutination test using sheep RBCs. While specific, it is more time-consuming and less sensitive than the modern Monospot test. * **C. Lymphocytosis in peripheral smear:** While the presence of **atypical lymphocytes (Downey cells)** is a hallmark of IM, it is a non-specific hematological finding seen in other viral infections (CMV, Toxoplasmosis, HIV). It is suggestive but not the most sensitive diagnostic test. * **D. Culture:** EBV is difficult to culture as it only grows in human B-lymphocytes. It is a research tool and is never used for routine clinical diagnosis. **High-Yield Clinical Pearls for NEET-PG:** * **Gold Standard:** The most specific test for EBV is the **EBV-specific antibody profile** (e.g., Anti-VCA IgM/IgG, Anti-EBNA). This is used if the Monospot is negative but IM is clinically suspected. * **False Negatives:** Monospot is often negative in children <4 years old and during the very early incubation period. * **Heterophile-Negative IM:** Most commonly caused by **Cytomegalovirus (CMV)**. * **Clinical Triad:** Fever, pharyngitis, and lymphadenopathy (posterior cervical). * **Warning:** Avoid Ampicillin/Amoxicillin in suspected IM, as it triggers a characteristic maculopapular rash.

Question 998: Which of the following oncogenic viruses has not been shown to be oncogenic in humans?

A. Hepatitis B virus
B. Epstein-Barr virus
C. Herpes simplex Type 2
D. Adenovirus (Correct Answer)

Explanation: **Explanation:** The correct answer is **Adenovirus**. While Adenoviruses (specifically types 12, 18, and 31) are highly oncogenic in laboratory animals (rodents) and can transform human cells in vitro, there is **no epidemiological or clinical evidence** linking them to naturally occurring cancers in humans. **Why the other options are incorrect:** * **Hepatitis B Virus (HBV):** A DNA virus strongly associated with **Hepatocellular Carcinoma (HCC)**. It integrates into the host genome and promotes oncogenesis through the HBx protein, which interferes with p53. * **Epstein-Barr Virus (EBV):** Known as the first human virus to be linked to cancer. It is associated with **Burkitt lymphoma**, Nasopharyngeal carcinoma, Hodgkin lymphoma, and B-cell lymphomas in immunocompromised patients. * **Herpes Simplex Type 2 (HSV-2):** While its role as a direct carcinogen is debated compared to HPV, it is historically considered a "co-factor" in the development of **Cervical Carcinoma**. It has demonstrated the ability to transform cells in experimental models and is classified among potentially oncogenic viruses in medical literature. **High-Yield Clinical Pearls for NEET-PG:** * **DNA Oncogenic Viruses:** HPV (16, 18), EBV, HBV, HHV-8 (Kaposi Sarcoma), and Merkel Cell Polyomavirus. * **RNA Oncogenic Viruses:** HTLV-1 (Adult T-cell Leukemia) and HCV (Hepatocellular Carcinoma). * **Mechanism:** Most DNA oncogenic viruses act by neutralizing tumor suppressor proteins like **p53** and **RB** (e.g., HPV E6 and E7 proteins). * **Adenovirus in Medicine:** Though not oncogenic in humans, it is a common cause of conjunctivitis, pharyngitis, and hemorrhagic cystitis.

Question 999: Intracytoplasmic and intranuclear inclusion bodies are characteristic findings in which viral infection?

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

Explanation: **Explanation:** The presence of both **intracytoplasmic and intranuclear inclusion bodies** is a classic histopathological hallmark of the **Measles virus** (a Paramyxovirus). These inclusions are composed of viral nucleocapsid aggregates. In Measles, these are specifically known as **Warthin-Finkeldey giant cells**, which are multinucleated giant cells found in lymphoid tissues and respiratory secretions. **Analysis of Options:** * **A. Measles (Correct):** It is one of the few viruses that produce inclusions in both the nucleus and cytoplasm. Another notable example is the Cytomegalovirus (CMV), which produces "Owl’s eye" intranuclear inclusions and smaller cytoplasmic ones. * **B. Mumps:** Like Measles, it is a Paramyxovirus, but it typically produces only **intracytoplasmic** inclusions. * **C. Rabies:** Characterized by pathognomonic **Negri bodies**, which are strictly **intracytoplasmic** eosinophilic inclusions found in pyramidal cells of the hippocampus and Purkinje cells of the cerebellum. * **D. Yellow Fever:** Characterized by **Councilman bodies**, which are eosinophilic apoptotic globules found in the cytoplasm of hepatocytes. These are not true viral inclusions but rather a sign of hepatocyte degeneration. **High-Yield NEET-PG Pearls:** * **Cowdry Type A (Intranuclear):** Seen in Herpes Simplex Virus (HSV) and Varicella-Zoster Virus (VZV). * **Cowdry Type B (Intranuclear):** Seen in Poliovirus and Adenovirus. * **Guarnieri bodies:** Intracytoplasmic inclusions seen in Variola (Smallpox) and Vaccinia. * **Henderson-Patterson bodies:** Large, intracytoplasmic, molluscum bodies seen in Molluscum Contagiosum. * **Torres bodies:** Intranuclear inclusions seen in Yellow Fever.

Question 1000: Which of the following is true regarding the hepatitis E virus?

A. It is seen in post-transfusion cases.
B. It is associated with increased mortality in pregnant females. (Correct Answer)
C. It is associated with the hepatitis B virus.
D. All of the above.

Explanation: **Explanation:** The **Hepatitis E Virus (HEV)** is a non-enveloped, single-stranded RNA virus belonging to the *Hepeviridae* family. It is primarily transmitted via the **fecal-oral route**, often through contaminated water. **Why Option B is correct:** HEV is notorious for causing **fulminant hepatic failure** in pregnant women, particularly during the third trimester. The mortality rate in this demographic can reach as high as **15–25%**. The exact pathogenesis is linked to hormonal changes and a shifted immune response (Th2 over Th1) during pregnancy, which leads to severe liver necrosis. **Why other options are incorrect:** * **Option A:** HEV is rarely associated with blood transfusions. Post-transfusion hepatitis is classically associated with **Hepatitis B (HBV)** and **Hepatitis C (HCV)**. * **Option C:** HEV is an independent virus. The virus that requires Hepatitis B for its replication and expression is **Hepatitis D (Delta virus)**, which exists as a co-infection or super-infection with HBV. **High-Yield Clinical Pearls for NEET-PG:** * **Genotypes:** Genotypes 1 and 2 are restricted to humans (epidemic); Genotypes 3 and 4 are zoonotic (pigs/boars). * **Chronicity:** HEV is usually acute and self-limiting, but **Genotype 3** can cause chronic hepatitis in immunocompromised individuals (e.g., organ transplant recipients). * **Diagnosis:** IgM anti-HEV is the gold standard for acute infection. * **Morphology:** It shows a characteristic "indentation and surface spikes" appearance under electron microscopy. * **Vaccine:** Hecolin (available in China) is the first vaccine developed against HEV.

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Virology — MCQs

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