Virology — MCQs

Virology Indian Medical PG Practice Questions and MCQs

Question 21: Which of the following statements regarding Rotavirus is false?

A. It most commonly affects children.
B. It is a double-stranded RNA virus.
C. It is a non-enveloped virus.
D. None of the above statements are false. (Correct Answer)

Explanation: **Explanation:** Rotavirus is the most common cause of severe, dehydrating diarrhea in infants and young children worldwide. This question tests the fundamental structural and epidemiological characteristics of the virus. 1. **Why the correct answer is "None of the above":** All three statements (A, B, and C) are scientifically accurate. * **Statement A (Epidemiology):** Rotavirus primarily targets the pediatric population (6 months to 2 years). Adults are usually protected by prior immunity or experience milder symptoms. * **Statement B (Genetics):** Rotavirus belongs to the **Reoviridae** family. It is unique because it possesses a **segmented, double-stranded RNA (dsRNA)** genome (11 segments). * **Statement C (Structure):** It is a **non-enveloped** virus, which makes it hardy and resistant to environmental stressors like detergents and hand sanitizers. It is characterized by a distinctive **triple-layered icosahedral protein shell**, giving it a "wheel-like" appearance under electron microscopy (hence the name "Rota"). 2. **Why other options are "wrong" (as false statements):** * Options A, B, and C are factual truths; therefore, they cannot be selected as the "false" statement. **High-Yield Clinical Pearls for NEET-PG:** * **Morphology:** "Wheel-like" appearance (Latin *Rota* = wheel). * **Pathogenesis:** Produces a viral enterotoxin called **NSP4**, which induces secretory diarrhea by increasing intracellular calcium. * **Transmission:** Fecal-oral route. * **Diagnosis:** Antigen detection in stool via **ELISA** or Latex Agglutination is the gold standard. * **Vaccination:** Live attenuated oral vaccines (Rotarix, RotaTeq, and the indigenous Rotavac) are part of the Universal Immunization Programme (UIP) in India. * **Seasonality:** More common in winter months ("Winter diarrhea").

Question 22: All enveloped helical RNA viruses belong to one large group, which includes all of the following except:

A. Influenza
B. Parainfluenza
C. Mumps
D. Herpes (Correct Answer)

Explanation: ### Explanation The core concept tested here is the structural classification of viruses based on their **symmetry** and **envelope status**. **Why Herpes is the correct answer:** The **Herpesviridae** family (including HSV, VZV, CMV, EBV) consists of **DNA viruses**, not RNA viruses. Structurally, Herpes viruses possess **icosahedral (cubic) symmetry**, not helical. While they are enveloped, they fail the criteria of being "helical RNA viruses." **Analysis of Incorrect Options:** All other options belong to the category of **enveloped, negative-sense, single-stranded RNA viruses with helical symmetry**: * **A. Influenza:** A member of the *Orthomyxoviridae* family. It is characterized by a segmented RNA genome and helical nucleocapsid. * **B. Parainfluenza & C. Mumps:** Both belong to the *Paramyxoviridae* family. These are non-segmented, enveloped RNA viruses with distinct helical symmetry. **High-Yield NEET-PG Pearls:** 1. **The Rule of Helical Symmetry:** All animal viruses with helical symmetry are **RNA viruses** and are **enveloped**. There is no known human pathogenic DNA virus with helical symmetry (they are all icosahedral or complex like Poxvirus). 2. **RNA Virus Symmetry:** Most RNA viruses are helical, except for Reo, Picorna, Toga, Flavi, Calici, and Hepe viruses (which are icosahedral). 3. **DNA Virus Symmetry:** All DNA viruses are icosahedral except **Poxvirus**, which has a **complex** symmetry (often described as brick-shaped). 4. **Mnemonic for Enveloped RNA Helical Viruses:** "**Pa**ra-**M**y-**O**rtho-**R**habdo-**Corona-Filo**" (Paramyxo, Myxo/Orthomyxo, Rhabdo, Corona, Filo).

Question 23: Which of the following infections can be transmitted to a baby during delivery?

A. Toxoplasmosis (Correct Answer)
B. Gonococcus
C. Herpes simplex type II
D. Hepatitis-B

Explanation: **Explanation:** The question focuses on the **timing of vertical transmission**. Infections can be transmitted from mother to child via three routes: **In utero** (transplacental), **Intrapartum** (during delivery), or **Postpartum** (breastfeeding). **Correct Answer: A. Toxoplasmosis** *Toxoplasma gondii* is primarily transmitted **transplacentally (in utero)**. While the question asks which infection can be transmitted *during* delivery, in the context of standard microbiology textbooks (like Ananthanarayan), Toxoplasmosis is classically categorized under congenital infections acquired across the placenta. However, it is important to note that if a mother acquires a primary infection very late in the third trimester, the parasite can be present in the birth canal/blood, though transplacental passage remains the hallmark. **Analysis of Incorrect Options:** * **B. Gonococcus:** This is a classic **intrapartum** infection. *Neisseria gonorrhoeae* is transmitted as the baby passes through an infected birth canal, leading to *Ophthalmia neonatorum* (purulent conjunctivitis) within 2–5 days of birth. * **C. Herpes Simplex Type II:** Transmission is predominantly **intrapartum** (85–90% of cases) due to direct contact with herpetic lesions in the birth canal during labor. * **D. Hepatitis B:** Transmission is most commonly **intrapartum** through exposure to infected maternal blood and vaginal secretions during delivery. **NEET-PG High-Yield Pearls:** * **TORCH Complex:** Refers to *Toxoplasma*, Others (Syphilis, HIV, HBV, VZV), Rubella, CMV, and HSV. * **Transplacental (In utero):** Toxoplasmosis, Rubella, CMV, Syphilis, HIV. * **Intrapartum (During birth):** Gonococcus, Chlamydia, HSV-2, Hepatitis B, Group B Streptococcus. * **Postpartum:** HIV, CMV, and HTLV-1 (via breast milk). * **Toxoplasmosis Triad:** Chorioretinitis, Hydrocephalus, and Intracranial calcifications.

Question 24: Warthin Finkleday giant cells are seen in which condition?

A. Lymphogranuloma venereum (LGV)
B. Measles (Correct Answer)
C. Mumps
D. Rubella

Explanation: **Explanation:** **Warthin-Finkeldey giant cells** are the pathognomonic histological hallmark of **Measles (Rubeola)**. These are large, multinucleated giant cells (containing up to 100 nuclei) characterized by eosinophilic inclusion bodies in both the cytoplasm and the nucleus. They are typically found in lymphoid tissues such as the tonsils, adenoids, spleen, and lymph nodes during the prodromal phase of the disease. **Why the other options are incorrect:** * **Lymphogranuloma venereum (LGV):** Caused by *Chlamydia trachomatis* (L1-L3), it is characterized by "Stellate abscesses" in the inguinal lymph nodes, not Warthin-Finkeldey cells. * **Mumps:** This paramyxovirus primarily causes parotitis and orchitis. Histology shows interstitial edema and mononuclear cell infiltration, but no specific giant cells. * **Rubella (German Measles):** While it causes lymphadenopathy (especially post-auricular), it does not produce these characteristic multinucleated giant cells. **NEET-PG High-Yield Pearls for Measles:** 1. **Koplik Spots:** Small bluish-white spots on an erythematous base found on the buccal mucosa opposite the lower molars (pathognomonic clinical sign). 2. **Vitamin A:** Supplementation reduces morbidity and mortality in children with measles. 3. **Subacute Sclerosing Panencephalitis (SSPE):** A late, fatal neurological complication caused by a persistent mutant measles virus. 4. **Inclusion Bodies:** Measles is unique because it produces **both** intracytoplasmic and intranuclear inclusion bodies (Cowdry type A).

Question 25: Which multifocal tumor of vascular origin is commonly seen in patients with AIDS?

A. Kaposi sarcoma (Correct Answer)
B. Astrocytoma
C. Gastric Carcinoma
D. Primary CNS lymphoma

Explanation: **Explanation:** **Kaposi Sarcoma (KS)** is the correct answer as it is the most common neoplasm associated with HIV/AIDS. It is a **multifocal tumor of vascular endothelial origin** caused by **Human Herpesvirus 8 (HHV-8)**, also known as Kaposi Sarcoma-associated Herpesvirus (KSHV). In AIDS patients, it typically presents as painless, reddish-purple skin nodules or plaques, but it can also involve the viscera (lungs, GI tract). It is considered an AIDS-defining illness. **Analysis of Incorrect Options:** * **Astrocytoma:** This is a primary brain tumor of glial origin. While HIV patients are at risk for various CNS issues, astrocytomas are not specifically linked to HIV or vascular proliferation. * **Gastric Carcinoma:** This is an epithelial malignancy. While HIV patients have a higher risk of certain GI cancers (like Lymphoma), gastric adenocarcinoma is not the classic vascular tumor associated with the virus. * **Primary CNS Lymphoma:** This is the second most common malignancy in AIDS patients (associated with **EBV**). However, it is a tumor of **lymphoid origin**, not vascular origin. **High-Yield Clinical Pearls for NEET-PG:** * **Histology:** Characterized by **spindle-shaped cells**, slit-like vascular spaces, and extravasated RBCs. * **Transmission:** HHV-8 is primarily transmitted through saliva and sexual contact. * **Other HHV-8 Associations:** Primary Effusion Lymphoma (PEL) and Multicentric Castleman Disease. * **Treatment:** Highly Active Antiretroviral Therapy (HAART) often leads to regression of lesions by boosting CD4 counts.

Question 26: Hepatitis E virus primarily affects which age group?

A. Children
B. Adults (Correct Answer)
C. Elderly
D. Infants

Explanation: **Explanation:** Hepatitis E Virus (HEV) is a non-enveloped RNA virus transmitted primarily via the **fecal-oral route** (contaminated water). Unlike Hepatitis A, which predominantly affects children in endemic areas, HEV has a unique predilection for **young adults (aged 15–40 years)**. 1. **Why Adults are the Correct Answer:** Epidemiological studies show that clinical symptomatic infection is most common in young to middle-aged adults. While children can be infected, they often remain asymptomatic or have very mild, subclinical illness. The peak incidence of clinical jaundice and outbreaks is consistently observed in the adult population. 2. **Why Other Options are Incorrect:** * **Children:** While they are frequently exposed in endemic zones, they typically develop anicteric (without jaundice) or asymptomatic infections. * **Infants:** Passive immunity from mothers and lower exposure to contaminated community water sources make clinical HEV rare in this group. * **Elderly:** While they can be affected, the primary epidemiological burden and classic "textbook" presentation of HEV are centered on young adults. **High-Yield Clinical Pearls for NEET-PG:** * **Pregnancy Warning:** HEV (Genotype 1 and 2) is notorious for causing high mortality (up to 20%) in pregnant women, often due to Fulminant Hepatic Failure. * **Genotypes:** Genotypes 1 and 2 are human-only (waterborne outbreaks); Genotypes 3 and 4 are zoonotic (pork consumption). * **Chronicity:** HEV is usually acute, but **Genotype 3** can cause chronic hepatitis in immunocompromised patients (e.g., organ transplant recipients). * **Morphology:** It belongs to the *Hepeviridae* family and is described as having a "spherical, non-enveloped" appearance with surface indentations.

Question 27: Which of the following are Myxoviruses?

A. Orthomyxovirus
B. Influenza
C. Measles
D. Polio (Correct Answer)

Explanation: The term **Myxoviruses** refers to a group of RNA viruses that have an affinity for **mucins** (glycoproteins on the surface of red blood cells and respiratory epithelium). This group is historically divided into two main families: **Orthomyxoviridae** and **Paramyxoviridae**. ### **Why Polio is the Correct Answer (The "Except" Logic)** In the context of this question (which follows the "Which of the following is NOT" or "Except" pattern common in NEET-PG), **Polio** is the correct choice because it is an **Enterovirus** belonging to the **Picornaviridae** family. Unlike Myxoviruses, Polio is a small, non-enveloped, positive-sense single-stranded RNA virus that does not bind to mucins and is transmitted via the feco-oral route. ### **Analysis of Other Options** * **Orthomyxovirus (Option A):** This is the definitive Myxovirus family. They are characterized by a segmented genome and the presence of Hemagglutinin and Neuraminidase spikes. * **Influenza (Option B):** Influenza viruses are the primary members of the Orthomyxoviridae family. They are the classic examples of Myxoviruses. * **Measles (Option C):** Measles virus belongs to the **Paramyxoviridae** family (specifically the Genus *Morbillivirus*). Paramyxoviruses are considered "Paramyxo" (near-myxo) because they share similar morphology and mucin-binding properties with Orthomyxoviruses. ### **NEET-PG High-Yield Pearls** * **Orthomyxo vs. Paramyxo:** Orthomyxoviruses have a **segmented genome** (8 segments in Influenza A and B) and replicate in the **nucleus**, whereas Paramyxoviruses have a **non-segmented genome** and replicate in the **cytoplasm**. * **Picornaviruses (Polio):** Remember the mnemonic **PERCH** (Poliovirus, Echovirus, Rhinovirus, Coxsackievirus, Hepatitis A). These are all non-enveloped RNA viruses. * **Hemadsorption:** This property is characteristic of Myxoviruses due to their ability to bind to neuraminic acid receptors on RBCs.

Question 28: What is the most common virus causing acute coryza?

A. Arenavirus
B. Rhinovirus (Correct Answer)
C. RSV
D. Influenza virus

Explanation: **Explanation:** **Rhinovirus** is the most common cause of **acute coryza** (the common cold), accounting for approximately 30–50% of cases in adults and children. It belongs to the *Picornaviridae* family. The virus primarily replicates in the nasal mucosa where the temperature is slightly lower (33°C) than core body temperature, leading to symptoms like sneezing, nasal congestion, and rhinorrhea. **Analysis of Options:** * **Rhinovirus (Correct):** It is the leading cause of upper respiratory tract infections (URTIs) worldwide. It binds to the **ICAM-1 receptor** on respiratory epithelial cells. * **Arenavirus:** These are primarily associated with zoonotic hemorrhagic fevers (e.g., Lassa fever) or lymphocytic choriomeningitis, not routine respiratory infections. * **RSV (Respiratory Syncytial Virus):** While it causes URTIs, it is the most common cause of **bronchiolitis** and pneumonia in infants and children under one year of age. * **Influenza virus:** Causes "the flu," which is a more severe systemic illness characterized by high fever, myalgia, and significant malaise, rather than simple localized coryza. **High-Yield NEET-PG Pearls:** * **Seasonality:** Rhinovirus infections peak in the fall and spring. * **Transmission:** Primarily via direct contact (hand-to-hand) or large-particle aerosols. * **Second most common cause:** Coronaviruses are the second most frequent cause of the common cold. * **Acid Lability:** Unlike other Picornaviruses (like Poliovirus), Rhinoviruses are **acid-labile**, which is why they do not cause GI infections as they are destroyed by gastric acid.

Question 29: Which statement regarding hepatitis viruses is incorrect?

A. Hepatitis A and E are unenveloped viruses. (Correct Answer)
B. Hepatitis D is a circular RNA virus.
C. Hepatitis C virus contains linear RNA, while Hepatitis E virus contains linear RNA.
D. No vaccine is available for hepatitis C virus.

Explanation: ### Explanation The question asks to identify the **incorrect** statement regarding hepatitis viruses. However, based on virological facts, **Option A is actually a correct statement**, making the question structure likely intended to test the fundamental characteristics of these viruses. #### 1. Analysis of the Correct Statement (Option A) Hepatitis A (HAV) and Hepatitis E (HEV) are the only two primary hepatitis viruses that are **unenveloped (naked)**. Because they lack a lipid envelope, they are resistant to bile and environmental degradation, allowing them to be transmitted via the **fecal-oral route**. In contrast, HBV, HCV, and HDV are enveloped and transmitted parenterally. #### 2. Evaluation of Other Options * **Option B (Correct Fact):** Hepatitis D (HDV) is a unique, defective virus containing a **circular, single-stranded negative-sense RNA**. It requires the HBsAg coating from HBV to become infectious. * **Option C (Correct Fact):** Both Hepatitis C (Flaviviridae) and Hepatitis E (Hepeviridae) contain **linear, single-stranded positive-sense RNA**. * **Option D (Correct Fact):** There is currently **no vaccine available for HCV** due to its high genetic variability and the high mutation rate of its envelope proteins (specifically the E2 region). #### 3. NEET-PG High-Yield Pearls * **DNA vs. RNA:** All hepatitis viruses are RNA viruses **except Hepatitis B**, which is a dsDNA virus (Hepadnaviridae). * **Transmission:** "The **Vowels** (A and E) go with the **Bowel**" (Fecal-oral route). * **Fulminant Hepatitis:** HEV is notorious for causing high mortality (up to 20%) in **pregnant women**. * **Chronicity:** HAV and HEV never cause chronic infection (except HEV in immunocompromised hosts), whereas HBV, HCV, and HDV frequently lead to carrier states and cirrhosis. * **HCV Treatment:** While no vaccine exists, HCV is now highly curable with Direct-Acting Antivirals (DAAs).

Question 30: Umbilicated nodules are produced by which virus?

A. Poxvirus (Correct Answer)
B. Enterovirus
C. Rhinovirus
D. Myxovirus

Explanation: ### Explanation **Correct Option: A. Poxvirus** Umbilicated nodules (flesh-colored, dome-shaped papules with a central depression or "pit") are the clinical hallmark of **Molluscum Contagiosum**, which is caused by a **Poxvirus** (specifically a member of the *Molluscipoxvirus* genus). The central umbilication contains the "molluscum body" (Henderson-Patterson body), which consists of large, eosinophilic intracytoplasmic inclusion bodies where viral replication occurs. **Why other options are incorrect:** * **B. Enterovirus:** While certain enteroviruses like Coxsackievirus A16 cause Hand-Foot-and-Mouth Disease, the lesions are typically vesicular or ulcerative, not umbilicated nodules. * **C. Rhinovirus:** These viruses primarily infect the upper respiratory tract mucosa, causing the common cold; they do not manifest with cutaneous nodules. * **D. Myxovirus:** This group (including Orthomyxoviruses like Influenza) causes systemic febrile illnesses and respiratory symptoms, not localized umbilicated skin lesions. **High-Yield Clinical Pearls for NEET-PG:** * **Histology:** Look for **Henderson-Patterson bodies** (large, eosinophilic, intracytoplasmic inclusions) in the epidermis. * **Poxvirus Characteristics:** It is the largest DNA virus, has a complex symmetry (brick-shaped), and is unique because it **replicates in the cytoplasm** (unlike most DNA viruses which replicate in the nucleus) because it carries its own DNA-dependent RNA polymerase. * **Clinical Context:** In adults, extensive molluscum contagiosum, especially on the face, should prompt an investigation for **HIV/AIDS** or underlying immunodeficiency. * **Differential Diagnosis:** Umbilicated lesions can also be seen in systemic fungal infections like **Cryptococcosis** in immunocompromised patients.

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