Virology — MCQs

Virology Indian Medical PG Practice Questions and MCQs

Question 1121: Which of the following is an oncogenic virus?

A. Cytomegalovirus (CMV)
B. Varicella-zoster virus (VZV)
C. Poliovirus
D. Epstein-Barr virus (EBV) (Correct Answer)

Explanation: **Explanation:** **Epstein-Barr Virus (EBV)**, also known as Human Herpesvirus 4 (HHV-4), is a well-established **oncogenic virus**. It was the first virus to be directly linked to human neoplasia. EBV infects B-lymphocytes via the CD21 receptor and remains latent. It promotes oncogenesis through viral proteins like **LMP-1** (Latent Membrane Protein 1), which mimics CD40 signaling to drive B-cell proliferation and inhibit apoptosis. **Analysis of Options:** * **Epstein-Barr Virus (EBV) (Correct):** It is associated with several malignancies, including **Burkitt Lymphoma** (starry-sky appearance), **Nasopharyngeal Carcinoma**, Hodgkin Lymphoma, and Primary CNS Lymphoma (especially in HIV patients). * **Cytomegalovirus (CMV):** While it causes significant morbidity in immunocompromised patients (retinitis, pneumonitis), it is not classified as a primary oncogenic virus. * **Varicella-zoster virus (VZV):** Causes chickenpox and shingles; it establishes latency in dorsal root ganglia but does not transform cells into a malignant state. * **Poliovirus:** An enterovirus that destroys motor neurons in the anterior horn of the spinal cord; it has no association with cancer. **High-Yield Clinical Pearls for NEET-PG:** * **Other DNA Oncogenic Viruses:** HPV (16, 18), Hepatitis B (HBV), Kaposi Sarcoma-associated Herpesvirus (HHV-8), and Merkel Cell Polyomavirus. * **RNA Oncogenic Viruses:** Hepatitis C (HCV) and Human T-cell Lymphotropic Virus-1 (HTLV-1). * **EBV Diagnostic Marker:** Heterophile antibody positive (Monospot test) in Infectious Mononucleosis. * **Burkitt Lymphoma Translocation:** t(8;14) involving the *c-myc* oncogene.

Question 1122: Which of the following are arboviral infections?

A. Chikungunya fever, West Nile fever, JE (Japanese Encephalitis), Sandfly fever (Correct Answer)
B. Chikungunya fever, JE (Japanese Encephalitis), Sandfly fever
C. West Nile fever, JE (Japanese Encephalitis), Sandfly fever
D. Chikungunya fever, West Nile fever, Sandfly fever

Explanation: **Explanation:** The term **Arbovirus** (Arthropod-borne virus) refers to a functional group of viruses that are transmitted to humans through the bite of infected hematophagous arthropods, such as mosquitoes, ticks, and sandflies. **Why Option A is correct:** All four diseases listed are classic examples of arboviral infections: * **Chikungunya fever:** Transmitted by *Aedes aegypti* and *Aedes albopictus* mosquitoes (Togaviridae). * **West Nile fever:** Transmitted by *Culex* mosquitoes (Flaviviridae). * **Japanese Encephalitis (JE):** Transmitted primarily by *Culex tritaeniorhynchus* (Flaviviridae). * **Sandfly fever (Pappataci fever):** Transmitted by the *Phlebotomus papataci* sandfly (Bunyaviridae/Phenuiviridae). **Why Options B, C, and D are incorrect:** These options are incomplete. While the diseases listed in them are indeed arboviral, they omit one of the four pathogens mentioned in the question. In NEET-PG, when multiple options contain correct facts, the most comprehensive list is the correct choice. **High-Yield Clinical Pearls for NEET-PG:** 1. **Major Families:** Most arboviruses belong to *Flaviviridae* (Dengue, JE, West Nile, Yellow Fever), *Togaviridae* (Chikungunya), or *Bunyaviridae* (Sandfly fever, Crimean-Congo Hemorrhagic Fever). 2. **Reservoirs:** For JE, pigs and water birds (Ardeid birds) act as amplifiers/reservoirs. Humans are "dead-end hosts." 3. **Vector Identification:** Remember the "Aedes" diseases (Dengue, Zika, Chikungunya, Yellow Fever) vs. "Culex" diseases (JE, West Nile, Filariasis). 4. **Kyasanur Forest Disease (KFD):** A high-yield Indian arbovirus transmitted by **ticks** (*Haemaphysalis spinigera*).

Question 1123: All of the following are true about Ebola virus except?

A. Incubation period is 2-21 days
B. Belongs to the Filoviridae family (Correct Answer)
C. Under electron microscopy, virions show a characteristic 'shepherd's crook' or 'thread-like' morphology
D. Investigation of choice is RT-PCR

Explanation: **Explanation:** The question asks for the "Except" statement, but based on virological facts, **Option B is actually a true statement.** Ebola virus indeed belongs to the **Filoviridae** family. In the context of this question, if Option B is marked as the "correct answer" (the false statement), it is likely a typographical error in the question source, as all four options provided are technically correct descriptions of the Ebola virus. **Breakdown of Options:** * **Option A (True):** The incubation period for Ebola Virus Disease (EVD) typically ranges from **2 to 21 days**. This is a critical timeframe for quarantine and monitoring of suspected cases. * **Option B (True):** Ebola, along with Marburg virus, belongs to the **Filoviridae** family. They are enveloped, non-segmented, negative-sense RNA viruses. * **Option C (True):** Under Electron Microscopy (EM), Filoviruses exhibit a highly pleomorphic, **thread-like (filamentous)** appearance. They often fold into structures resembling a **'shepherd’s crook'**, the letter '6', or a 'U'. * **Option D (True):** **RT-PCR** (Reverse Transcription Polymerase Chain Reaction) is the **investigation of choice** for acute diagnosis, as it can detect the viral RNA in blood or body fluids shortly after symptom onset. **High-Yield Clinical Pearls for NEET-PG:** * **Transmission:** Primarily through direct contact with infected blood, secretions, or organs (including fruit bats, the natural reservoir). * **Pathogenesis:** Causes severe hemorrhagic fever by infecting endothelial cells and causing a "cytokine storm." * **Biosafety Level:** Ebola requires **BSL-4** containment (the highest level). * **Vaccine:** The **rVSV-ZEBOV** vaccine is used for prevention during outbreaks.

Question 1124: A 24-hour history of fever in an infant is followed by the appearance of a maculopapular rash and erythema on the face. What other condition can be caused by the organism responsible for these symptoms?

A. Acute myeloid leukemia
B. Cytomegalovirus infection
C. Pure red cell aplasia (Correct Answer)
D. Hairy cell leukemia

Explanation: **Explanation:** The clinical presentation of fever followed by a facial maculopapular rash (classically described as a **"slapped-cheek" appearance**) in an infant is diagnostic of **Erythema Infectiosum (Fifth Disease)**. This condition is caused by **Parvovirus B19**, a small, non-enveloped DNA virus. **Why the correct answer is right:** Parvovirus B19 specifically targets and infects **erythroid progenitor cells** in the bone marrow by binding to the **P-antigen** (globoside). In healthy individuals, this causes a transient drop in hemoglobin. However, in patients with underlying hemolytic anemias (like Sickle Cell Disease) or immunocompromised states, it can lead to a cessation of red blood cell production, resulting in a **Transient Aplastic Crisis** or **Pure Red Cell Aplasia (PRCA)**. **Analysis of Incorrect Options:** * **A & D (Leukemias):** Acute myeloid leukemia and Hairy cell leukemia are neoplastic proliferations of leukocytes. Parvovirus B19 is not oncogenic and does not cause these malignancies. * **B (Cytomegalovirus):** While CMV is a common viral infection in infants, it typically presents with hepatosplenomegaly, jaundice, or mononucleosis-like symptoms, rather than the classic "slapped-cheek" rash. **High-Yield NEET-PG Pearls:** * **Receptor:** P-antigen (Globoside) on RBCs. * **Pregnancy:** Infection during pregnancy can lead to **Hydrops Fetalis** due to severe fetal anemia and high-output heart failure. * **Adults:** Often presents as symmetrical **arthralgia/arthritis** (mimicking Rheumatoid Arthritis). * **Morphology:** Look for **"Giant Pronormoblasts"** with viral inclusions in the bone marrow.

Question 1125: Which virus is the leading cause of the croup syndrome in young children and, when infecting mammalian cells in culture, will hemadsorb red blood cells?

A. Group B coxsackievirus
B. Rotavirus
C. Parainfluenza virus (Correct Answer)
D. Adenovirus

Explanation: **Explanation:** The correct answer is **Parainfluenza virus (PIV)**. This virus belongs to the *Paramyxoviridae* family and is the most common cause of **Croup (Laryngotracheobronchitis)** in children aged 6 months to 3 years. **Why it is correct:** 1. **Clinical Presentation:** PIV (specifically Type 1 and 2) causes subglottic edema, leading to the classic triad of barking cough, inspiratory stridor, and hoarseness. 2. **Hemadsorption:** PIV possesses a **Hemagglutinin-Neuraminidase (HN) protein** on its envelope. When the virus infects a cell culture, these viral proteins are expressed on the host cell membrane. If red blood cells (RBCs) are added to the culture, they adhere to the surface of the infected cells—a phenomenon known as **hemadsorption**. This is a key diagnostic laboratory feature for Paramyxoviruses and Orthomyxoviruses. **Why other options are incorrect:** * **Group B Coxsackievirus:** Primarily associated with pleurodynia (Bornholm disease), myocarditis, and herpangina; it does not cause croup or exhibit hemadsorption. * **Rotavirus:** The leading cause of severe dehydrating diarrhea in infants; it is a non-enveloped Reovirus. * **Adenovirus:** While it can cause respiratory infections (pharyngoconjunctival fever), it is a DNA virus that does not typically cause croup and does not hemadsorb. **High-Yield NEET-PG Pearls:** * **Steeple Sign:** X-ray finding in Croup showing subglottic narrowing. * **Genome:** PIV is a pleomorphic, enveloped, negative-sense ssRNA virus. * **Syncytia formation:** Like other Paramyxoviruses, PIV induces cell-to-cell fusion (multinucleated giant cells) via its Fusion (F) protein.

Question 1126: What is the animal reservoir for the swine influenza virus?

A. Field mice
B. Urban rats
C. Pigs (Correct Answer)
D. Calomys callosus

Explanation: **Explanation:** The correct answer is **Pigs (Option C)**. Swine influenza is a highly contagious respiratory disease caused by Type A influenza viruses. Pigs are the natural **primary reservoir** for these viruses. In virology, pigs are often referred to as "mixing vessels" because their respiratory epithelial cells possess receptors for both avian (α2,3-linked sialic acid) and human (α2,4-linked sialic acid) influenza viruses. This allows for **genetic reassortment** (Antigenic Shift), which can lead to the emergence of novel pandemic strains, such as the 2009 H1N1 pandemic. **Analysis of Incorrect Options:** * **Field mice (Option A):** These are common reservoirs for Hantaviruses (causing HFRS) and Scrub Typhus (*Orientia tsutsugamushi*). * **Urban rats (Option B):** These are classic reservoirs for *Leptospira*, *Yersinia pestis* (Plague), and Lassa fever. * **Calomys callosus (Option D):** This specific large vesper mouse is the primary reservoir for the **Machupo virus**, which causes Bolivian Hemorrhagic Fever. **High-Yield Clinical Pearls for NEET-PG:** * **Antigenic Shift:** Major genetic changes (reassortment) occurring only in Influenza A, leading to pandemics. * **Antigenic Drift:** Minor point mutations occurring in both Influenza A and B, leading to seasonal epidemics. * **Diagnosis:** Real-time RT-PCR is the gold standard for identifying swine flu (H1N1). * **Treatment:** Neuraminidase inhibitors like **Oseltamivir** (Tamiflu) are the drug of choice. * **Hemagglutinin (H):** Responsible for viral attachment to host cells. * **Neuraminidase (N):** Responsible for the release of progeny virions from the host cell.

Question 1127: Which of the following is a DNA virus?

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

Explanation: **Explanation:** The correct answer is **Hepatitis B virus (HBV)**. Among the primary hepatitis viruses (A through E), HBV is the only one that contains a **DNA genome**. Specifically, it is a partially double-stranded circular DNA virus belonging to the *Hepadnaviridae* family. It replicates via an RNA intermediate using the enzyme reverse transcriptase. **Analysis of Options:** * **Hepatitis A (HAV):** A member of the *Picornaviridae* family, it is a non-enveloped, single-stranded, positive-sense **RNA** virus. It is typically transmitted via the fecal-oral route. * **Hepatitis C (HCV):** A member of the *Flaviviridae* family, it is an enveloped, single-stranded, positive-sense **RNA** virus. It is a leading cause of chronic liver disease and cirrhosis. * **Hepatitis D (HDV):** A defective **RNA** virus (genus *Deltavirus*) that requires the HBsAg (Hepatitis B surface antigen) coat to become infectious. It can only cause infection as a co-infection or superinfection with HBV. **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic:** All Hepatitis viruses are RNA except **B** (DNA). * **HBV Structure:** It is the only DNA virus that utilizes **reverse transcriptase** but is not a Retrovirus. * **Dane Particle:** The complete infectious virion of HBV is known as the Dane particle (42 nm). * **Transmission:** HBV, HCV, and HDV are transmitted parenterally/sexually, while HAV and HEV are transmitted via the fecal-oral route ("The **Vowels** hit the **Bowels**"). * **Hepatitis E:** While it is an RNA virus, remember that HEV is particularly associated with high mortality in pregnant women.

Question 1128: During the window period of a patient with AIDS, which of the following tests are typically negative?

A. ELISA is negative
B. Western Blot is negative
C. Both ELISA and Western Blot are negative (Correct Answer)
D. PCR is negative

Explanation: **Explanation:** The **Window Period** in HIV infection refers to the time interval between the initial infection and the point when the body produces enough antibodies to be detected by standard screening and confirmatory tests. 1. **Why Option C is correct:** Both **ELISA** (Enzyme-Linked Immunosorbent Assay) and **Western Blot** are antibody-based tests. During the window period (typically 3 to 12 weeks), the patient is highly infectious and the virus is replicating rapidly, but the immune system has not yet undergone **seroconversion**. Therefore, tests that look for anti-HIV antibodies will yield a false-negative result. 2. **Why other options are incorrect:** * **Options A & B:** While both are negative, Option C is the most comprehensive answer as it encompasses both screening (ELISA) and confirmatory (Western Blot) antibody assays. * **Option D (PCR):** PCR (Polymerase Chain Reaction) detects viral nucleic acids (DNA/RNA). It is **positive** during the window period because it identifies the virus itself rather than the host's immune response. PCR is the earliest test to become positive (as early as 10–14 days post-exposure). **High-Yield Clinical Pearls for NEET-PG:** * **Earliest Marker:** HIV-RNA (detected by NAT/PCR) is the first marker to appear. * **p24 Antigen:** This is a viral core protein that appears before antibodies but after RNA. The **4th Generation ELISA** (p24 Ag + Antibody) significantly shortens the window period. * **Screening vs. Confirmatory:** ELISA is the standard screening test (High Sensitivity), while Western Blot was traditionally the gold-standard confirmatory test (High Specificity). * **Diagnosis in Infants:** In infants born to HIV-positive mothers, antibody tests are unreliable due to the persistence of maternal IgG. **DNA-PCR** is the investigation of choice.

Question 1129: What is the recommended follow-up period for an individual who has come into contact with a confirmed case of coronavirus (COVID-19)?

A. 7 days
B. 21 days
C. 42 days
D. 14 days (Correct Answer)

Explanation: **Explanation:** The correct answer is **14 days**. This duration is based on the known **incubation period** of SARS-CoV-2 (the virus causing COVID-19). 1. **Why 14 days is correct:** The incubation period is the time from exposure to the virus to the onset of symptoms. For COVID-19, the incubation period typically ranges from 2 to 14 days, with an average of 5–6 days. Public health guidelines (WHO and MoHFW) established a 14-day quarantine/follow-up period to ensure that almost all exposed individuals (99% of cases) would manifest symptoms or test positive within this window. 2. **Analysis of Incorrect Options:** * **7 days (A):** While many patients develop symptoms by day 5 or 7, a significant percentage of "slow progressors" would be missed if follow-up ended this early. * **21 days (B) & 42 days (C):** These durations are unnecessarily long for routine follow-up. 21 days is more characteristic of the monitoring period for Ebola Virus Disease, while 42 days (two incubation cycles) is often used to declare an outbreak "over" in a specific region. **High-Yield Clinical Pearls for NEET-PG:** * **Incubation Period:** 2–14 days (Median: ~5.1 days). * **Mode of Transmission:** Primarily respiratory droplets and fomites; airborne transmission possible in closed spaces/aerosol-generating procedures. * **Receptor:** SARS-CoV-2 binds to the **ACE-2 receptor** (Angiotensin-Converting Enzyme 2) found in the lungs, heart, and kidneys. * **Gold Standard Test:** Real-time Reverse Transcription Polymerase Chain Reaction (**rRT-PCR**) targeting genes like E (Envelope), RdRp, or N (Nucleocapsid).

Question 1130: Spongiform degeneration of the cerebrum occurs in which of the following conditions?

A. Creutzfeldt-Jakob disease (Correct Answer)
B. Subacute sclerosing panencephalitis
C. Fatal familial insomnia
D. Cerebral toxoplasmosis

Explanation: **Explanation:** The correct answer is **Creutzfeldt-Jakob disease (CJD)**. **1. Why CJD is correct:** Creutzfeldt-Jakob disease is a human prion disease caused by the accumulation of misfolded proteins (PrPSc). The hallmark pathological feature of prion diseases is **spongiform degeneration**, characterized by the formation of microscopic vacuoles within the neuropil of the gray matter (cerebrum and cerebellum). This occurs without an inflammatory response, leading to rapidly progressive dementia and myoclonus. **2. Analysis of Incorrect Options:** * **Subacute sclerosing panencephalitis (SSPE):** A late complication of Measles virus. Histology shows **Cowdry type A intranuclear inclusion bodies** and perivascular cuffing, not spongiform changes. * **Fatal familial insomnia (FFI):** While also a prion disease, the primary pathology in FFI is localized to the **thalamus** (neuronal loss and gliosis) rather than widespread spongiform degeneration of the cerebrum. * **Cerebral toxoplasmosis:** Caused by the parasite *Toxoplasma gondii*. It typically presents as **ring-enhancing lesions** on imaging and focal necrotizing encephalitis, not spongiform change. **3. NEET-PG High-Yield Pearls:** * **Prions:** They are proteinaceous infectious particles devoid of nucleic acids. They are highly resistant to standard sterilization (require autoclaving at 134°C or 1N NaOH). * **Triad of CJD:** Rapidly progressive dementia, myoclonus, and periodic sharp-wave complexes on EEG. * **Diagnosis:** Detection of **14-3-3 protein** in CSF is a high-yield diagnostic marker. * **Kuru:** Another prion disease associated with ritualistic cannibalism, primarily affecting the cerebellum (causing ataxia).

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