Virology — MCQs

A 27-year-old man with a history of intravenous drug use has been infected with the hepatitis B virus for the past 6 years and has not been ill. He presents with nausea, vomiting, and passage of dark-colored urine for the past week. Physical examination reveals scleral icterus and mild jaundice. Neurologic examination shows a confused, somnolent man oriented only to person. He exhibits asterixis. Laboratory studies show total protein, 5 g/dL; albumin, 2.7 g/dL; AST, 2342 U/L; ALT, 2150 U/L; alkaline phosphatase, 233 U/L; total bilirubin, 8.3 mg/dL; and direct bilirubin, 4.5 mg/dL. Superinfection with which of the following viruses has most likely occurred in this man?

Q784Easy

Which virus has the smallest genome?

Q785Medium

Regarding hepatitis E, which of the following statements is true?

Q786Easy

Which of the following is not a cultivable virus?

Q787Easy

All of the following are classified as Picornaviruses except:

Q788Easy

Which tests are used for the diagnosis of chickenpox?

Q789Easy

Through which cells does the Human Immunodeficiency Virus (HIV) spread in the body?

Q790Easy

Which of the following is a prion disease?

Virology Indian Medical PG Practice Questions and MCQs

Question 781: All of the following belong to arboviruses group except?

A. Bunyavirus
B. Paramyxovirus (Correct Answer)
C. Reovirus
D. Alphavirus

Explanation: **Explanation:** The term **Arbovirus** (Arthropod-borne virus) is an ecological classification rather than a taxonomic one. It refers to viruses that are transmitted to humans via the bite of hematophagous (blood-sucking) arthropods, such as mosquitoes, ticks, and sandflies. **Why Paramyxovirus is the correct answer:** **Paramyxoviruses** (e.g., Measles, Mumps, RSV) are transmitted primarily through **respiratory droplets** or direct contact. They do not require an arthropod vector for their life cycle or transmission. Therefore, they do not belong to the arbovirus group. **Analysis of incorrect options:** * **Bunyavirus (Option A):** This family includes many arboviruses, such as the Crimean-Congo hemorrhagic fever virus (transmitted by ticks) and California encephalitis virus (transmitted by mosquitoes). * **Reovirus (Option C):** While many Reoviruses are enteric, the genus *Orbivirus* (e.g., Bluetongue virus) and *Coltivirus* (e.g., Colorado tick fever virus) are classic arboviruses. * **Alphavirus (Option D):** This genus belongs to the Togaviridae family and consists almost entirely of arboviruses, including Chikungunya, Eastern Equine Encephalitis (EEE), and Ross River virus. **High-Yield Clinical Pearls for NEET-PG:** * **Major Arbovirus Families:** Flaviviridae (Dengue, Zika, West Nile, Yellow Fever), Togaviridae (Chikungunya), Bunyaviridae, and Reoviridae. * **Exception to remember:** **Roboviruses** (Rodent-borne) like Hantavirus and Lassa fever are often confused with arboviruses but are transmitted via rodent excreta, not arthropods. * **Yellow Fever:** The first arbovirus to be discovered; the **Aedes aegypti** mosquito is its primary vector. * **Japanese Encephalitis:** The most common cause of epidemic viral encephalitis in India, transmitted by **Culex** mosquitoes.

Question 782: Which of the following best describes adenovirus?

A. Nonenveloped, double-stranded DNA virus with fibers at its vertices (Correct Answer)
B. Nonenveloped, double-stranded, circular DNA virus
C. Enveloped, single-stranded, negative-sense RNA virus
D. Enveloped, double-stranded, linear DNA virus with glycoprotein spikes

Explanation: **Explanation:** Adenoviruses are a significant cause of respiratory, ocular, and gastrointestinal infections. Their structure is highly characteristic and a frequent high-yield topic in NEET-PG. **1. Why Option A is Correct:** Adenoviruses are **non-enveloped** viruses with an **icosahedral** capsid. Their genome consists of **linear, double-stranded DNA (dsDNA)**. A defining feature is the presence of toxic **"fibers"** (penton fibers) projecting from the 12 vertices of the capsid. These fibers act as hemagglutinins and mediate attachment to host cell receptors (CAR - Coxsackie-Adenovirus Receptor). **2. Why the Other Options are Incorrect:** * **Option B:** Describes **Papovaviridae** (e.g., HPV). While non-enveloped and dsDNA, their genome is **circular**, not linear, and they lack the characteristic vertex fibers. * **Option C:** Describes many respiratory viruses like **Orthomyxoviridae** (Influenza) or **Paramyxoviridae**. Adenoviruses are DNA viruses, not RNA. * **Option D:** Describes **Herpesviridae**. While Herpesviruses have linear dsDNA, they are **enveloped**, whereas Adenoviruses are "naked." **3. Clinical Pearls for NEET-PG:** * **Transmission:** Respiratory droplets, feco-oral route, or contaminated fomites (e.g., ophthalmologist’s equipment). * **Key Syndromes:** * **Pharyngoconjunctival fever:** Characterized by the triad of fever, pharyngitis, and conjunctivitis (Types 3, 7). * **Epidemic Keratoconjunctivitis (EKC):** "Shipyard eye" (Types 8, 19, 37). * **Acute Hemorrhagic Cystitis:** Leading cause of hematuria in children (Types 11, 21). * **Gastroenteritis:** Types 40 and 41 are significant causes of infantile diarrhea. * **Cytopathology:** Produces prominent **intranuclear inclusion bodies** (Basophilic/Cowdry Type B).

Question 783: A 27-year-old man with a history of intravenous drug use has been infected with the hepatitis B virus for the past 6 years and has not been ill. He presents with nausea, vomiting, and passage of dark-colored urine for the past week. Physical examination reveals scleral icterus and mild jaundice. Neurologic examination shows a confused, somnolent man oriented only to person. He exhibits asterixis. Laboratory studies show total protein, 5 g/dL; albumin, 2.7 g/dL; AST, 2342 U/L; ALT, 2150 U/L; alkaline phosphatase, 233 U/L; total bilirubin, 8.3 mg/dL; and direct bilirubin, 4.5 mg/dL. Superinfection with which of the following viruses has most likely occurred in this man?

A. Hepatitis A virus (HAV)
B. Hepatitis C virus (HCV)
C. Hepatitis D virus (HDV) (Correct Answer)
D. Hepatitis E virus (HEV)

Explanation: ### Explanation **Correct Answer: C. Hepatitis D virus (HDV)** The patient is a chronic carrier of Hepatitis B Virus (HBV) who has developed **Fulminant Hepatic Failure (FHF)**, evidenced by severe transaminitis (AST/ALT >2000 U/L), hyperbilirubinemia, and **hepatic encephalopathy** (confusion, asterixis, somnolence). In a known HBV carrier, a sudden clinical deterioration usually points toward **HDV superinfection**. HDV is a defective RNA virus that requires the HBsAg coat to infect hepatocytes. When a chronic HBV carrier is infected with HDV (superinfection), it often leads to severe acute hepatitis, a higher risk of fulminant liver failure, and rapid progression to cirrhosis compared to co-infection (simultaneous infection of HBV and HDV). **Why other options are incorrect:** * **HAV & HEV:** These are transmitted via the fecal-oral route. While they cause acute hepatitis, they do not specifically target HBV carriers nor typically cause such dramatic deterioration in a patient with a high-risk profile (IV drug use). * **HCV:** While common in IV drug users, HCV rarely causes fulminant hepatitis. It typically leads to chronic infection rather than an acute, life-threatening presentation with encephalopathy. **NEET-PG High-Yield Pearls:** * **Co-infection:** HBV + HDV acquired at the same time. Usually self-limiting; <5% progress to chronicity. * **Superinfection:** HDV acquired by a chronic HBV carrier. High risk of fulminant hepatitis (as seen here) and >80% risk of chronic HDV infection. * **Marker of HDV:** HDAg and HDV RNA are the earliest markers. * **Asterixis (Flapping tremors):** A hallmark sign of Stage II hepatic encephalopathy due to ammonia accumulation.

Question 784: Which virus has the smallest genome?

A. Reovirus
B. Parvovirus (Correct Answer)
C. Picornavirus
D. HIV

Explanation: **Explanation:** The size of a viral genome is determined by the number of nucleotides (for single-stranded) or base pairs (for double-stranded) it contains. Among the options provided, **Parvovirus** is the correct answer. **Why Parvovirus is correct:** Parvoviruses are the smallest known DNA viruses infecting humans. They possess a single-stranded DNA (ssDNA) genome that is approximately **5 kb (kilobases)** in length. Their physical size is also remarkably small, measuring about 18–26 nm in diameter. Specifically, Parvovirus B19 is the most clinically significant member of this family. **Analysis of Incorrect Options:** * **Reovirus:** These are double-stranded RNA (dsRNA) viruses with a segmented genome. Their genome size is significantly larger, approximately **18–30 kbp**. * **Picornavirus:** While "Pico" means small, these are small RNA viruses (e.g., Poliovirus). Their positive-sense ssRNA genome is roughly **7–8 kb**, which is larger than that of Parvovirus. * **HIV (Retrovirus):** HIV has a complex genome consisting of two identical strands of positive-sense ssRNA, totaling about **9.7 kb**. **High-Yield Clinical Pearls for NEET-PG:** * **Smallest DNA Virus:** Parvovirus (ssDNA, non-enveloped). * **Largest DNA Virus:** Poxvirus (dsDNA, enveloped; visible under light microscopy). * **Smallest RNA Virus:** Picornavirus (specifically Enteroviruses/Rhinoviruses). * **Clinical Correlation:** Parvovirus B19 causes **Erythema Infectiosum** (Fifth disease/Slapped-cheek appearance), **Aplastic Crisis** in patients with chronic hemolytic anemias (e.g., Sickle Cell), and **Hydrops Fetalis** if contracted during pregnancy. It targets the P-antigen on erythroid progenitor cells.

Question 785: Regarding hepatitis E, which of the following statements is true?

A. It commonly occurs with Hepatitis B co-infection.
B. It is caused by a single-stranded DNA virus.
C. It frequently occurs along with HIV co-infection.
D. It increases mortality in pregnant individuals. (Correct Answer)

Explanation: **Explanation:** **Hepatitis E Virus (HEV)** is a major cause of enterically transmitted hepatitis worldwide. The correct answer is **Option D** because HEV infection in pregnant individuals, particularly during the third trimester, is associated with a high risk of **Fulminant Hepatic Failure (FHF)**. The mortality rate in this demographic can reach as high as **15–25%**, likely due to a combination of hormonal changes and altered immune responses (Th2 bias). **Analysis of Incorrect Options:** * **Option A:** Hepatitis **D** (not E) is the virus that requires Hepatitis B surface antigen (HBsAg) for its envelope and occurs as a co-infection or super-infection with HBV. * **Option B:** HEV is a **non-enveloped, single-stranded RNA virus** belonging to the *Hepeviridae* family. It is not a DNA virus. * **Option C:** While HEV can cause chronic infection in immunocompromised patients (like those with HIV or organ transplants), it is not classically defined by a frequent epidemiological association with HIV in the same way that HBV or HCV (blood-borne) are. **High-Yield Clinical Pearls for NEET-PG:** * **Transmission:** Fecal-oral route (contaminated water is the most common vehicle). * **Zoonosis:** HEV Genotype 3 is associated with the consumption of undercooked pork/deer meat. * **Chronicity:** HEV usually causes acute self-limiting hepatitis, but **Genotype 3** can cause chronic hepatitis in immunocompromised individuals. * **Diagnosis:** Detection of IgM anti-HEV or HEV RNA by PCR. * **Key Association:** Always link "Hepatitis E" with "High mortality in pregnancy" and "Water-borne epidemics."

Question 786: Which of the following is not a cultivable virus?

A. Papova
B. Parvovirus B-19 (Correct Answer)
C. Herpes
D. Adenovirus

Explanation: **Explanation:** The correct answer is **Parvovirus B-19**. **1. Why Parvovirus B-19 is the correct answer:** Parvovirus B-19 is notoriously difficult to grow in standard laboratory cell lines. It has a highly specific tropism for **erythroid progenitor cells** (specifically in the bone marrow) because it uses the **P-antigen (Globoside)** as its cellular receptor. Since standard cell cultures (like HeLa or Vero cells) lack these specific erythroid precursors and the necessary cellular environment for its replication, it is considered "non-cultivable" in routine diagnostic virology. Diagnosis is instead primarily achieved via PCR or serology (IgM/IgG). **2. Why the other options are incorrect:** * **Papova (A):** This family (including HPV and Polyomavirus) can be grown in specialized organotypic (raft) cultures, though it is technically challenging. * **Herpes (C):** Herpes Simplex Virus (HSV) is one of the easiest viruses to cultivate. It grows rapidly on various cell lines (e.g., Human Embryonic Lung, Hep-2), producing characteristic **Cowdry Type A** inclusion bodies and syncytia. * **Adenovirus (D):** These are easily cultivated in epithelial cell lines (like HEK 293 or HeLa), where they produce typical "grape-like clusters" as a cytopathic effect (CPE). **High-Yield Clinical Pearls for NEET-PG:** * **Receptor:** Parvovirus B-19 binds to **P-antigen**; individuals lacking this antigen are naturally resistant. * **Clinical Spectrum:** Causes **Erythema Infectiosum** (Slapped-cheek appearance), **Aplastic Crisis** in sickle cell patients, and **Hydrops Fetalis** in pregnancy. * **Other Non-cultivable/Difficult viruses:** Hepatitis B, Hepatitis C, and Noroviruses are also traditionally difficult or impossible to grow in routine cell cultures.

Question 787: All of the following are classified as Picornaviruses except:

A. Enterovirus 70
B. Coxsackievirus
C. Rhinovirus
D. Chickenpox virus (Correct Answer)

Explanation: The correct answer is **Chickenpox virus** (Varicella-Zoster Virus). ### **Explanation** The classification of viruses is a high-yield topic for NEET-PG. The **Picornaviridae** family consists of small (pico), non-enveloped, positive-sense single-stranded RNA viruses. **Chickenpox virus** (Varicella-Zoster Virus) belongs to the **Herpesviridae** family. Unlike Picornaviruses, it is a large, enveloped, double-stranded DNA virus. It is specifically classified under the *Alphaherpesvirinae* subfamily and is known for its ability to establish latency in the dorsal root ganglia. ### **Analysis of Options** * **Enterovirus 70:** A member of the *Enterovirus* genus within the Picornaviridae family. It is classically associated with Acute Hemorrhagic Conjunctivitis (AHC). * **Coxsackievirus:** Part of the *Enterovirus* genus. It is divided into Group A (Herpangina, Hand-foot-mouth disease) and Group B (Pleurodynia, Myocarditis). * **Rhinovirus:** The most common cause of the "common cold," these are acid-labile Picornaviruses that replicate best at 33°C (nasal temperature). ### **Clinical Pearls for NEET-PG** * **Picornavirus Mnemonic (PERCH):** **P**oliovirus, **E**cho virus, **R**hinovirus, **C**oxsackievirus, and **H**epatitis A virus. * **Enterovirus 71** is a major cause of neurological disease and Hand-foot-mouth disease outbreaks. * **Replication Site:** Unlike most RNA viruses that replicate in the cytoplasm, Picornaviruses follow this rule, but remember that **Influenza** and **Retroviruses** are exceptions that replicate in the nucleus. * **VZV (Chickenpox):** Characterized by a "dewdrop on a rose petal" rash with pleomorphic stages (macules, papules, and vesicles) present simultaneously.

Question 788: Which tests are used for the diagnosis of chickenpox?

A. FAMA
B. ELISA
C. PCR
D. All of the above (Correct Answer)

Explanation: Chickenpox is caused by the **Varicella-Zoster Virus (VZV)**. While the diagnosis is primarily clinical based on the characteristic "pleomorphic" rash (crops of vesicles in different stages), laboratory confirmation is essential in atypical cases or immunocompromised patients. ### **Explanation of Options:** * **PCR (Polymerase Chain Reaction):** This is currently the **gold standard** and the most sensitive/specific method for detecting VZV DNA. It is typically performed on swabs from the base of a vesicle. * **ELISA (Enzyme-Linked Immunosorbent Assay):** This is the most common serological test used to detect **IgM antibodies** (indicating acute infection) or **IgG antibodies** (indicating past infection or immunity). * **FAMA (Fluorescent Antibody to Membrane Antigen):** This is considered the **reference standard** for determining protective immunity. It is highly sensitive for detecting surface antibodies but is technically demanding and usually reserved for research settings. Since all three methods—molecular (PCR), serological (ELISA), and specialized antibody detection (FAMA)—are valid diagnostic tools, **Option D (All of the above)** is correct. ### **High-Yield Clinical Pearls for NEET-PG:** 1. **Tzanck Smear:** A rapid bedside test showing **Multinucleated Giant Cells** with **Cowdry Type A** intranuclear inclusion bodies. Note: This does not differentiate between VZV and HSV. 2. **Characteristic Rash:** Described as **"Dewdrops on a rose petal"** appearance. 3. **Centripetal Distribution:** The rash is most dense on the trunk and least dense on the distal extremities (opposite of Smallpox). 4. **Infectivity:** Patients are infectious from **1–2 days before** the rash appears until **all vesicles have crusted over**.

Question 789: Through which cells does the Human Immunodeficiency Virus (HIV) spread in the body?

A. Suppressor T-cells
B. Carrier T-cells
C. Helper T-cells (Correct Answer)
D. Killer T-cells

Explanation: **Explanation:** The Human Immunodeficiency Virus (HIV) primarily targets cells expressing the **CD4 receptor** on their surface [1], [2]. The hallmark of HIV pathogenesis is the progressive depletion of **Helper T-cells (CD4+ T lymphocytes)** [1], [3]. **1. Why Helper T-cells are the correct answer:** HIV uses its envelope glycoprotein **gp120** to bind specifically to the CD4 molecule [4]. Helper T-cells have the highest density of these receptors. Once bound, the virus utilizes co-receptors (**CCR5** in early infection/macrophage-tropic strains or **CXCR4** in late infection/T-tropic strains) to enter the cell [1]. By infecting and destroying these cells, HIV collapses the adaptive immune system, as Helper T-cells are essential for activating both B-cells (antibody production) and Cytotoxic T-cells [3]. **2. Why the other options are incorrect:** * **Suppressor T-cells (CD8+):** These cells lack the CD4 receptor. While their function is altered due to the lack of "help" from CD4 cells, they are not the primary targets for viral entry. * **Killer T-cells (Cytotoxic T-cells/CD8+):** These cells also lack CD4 receptors. In fact, during the early stages of infection, Killer T-cells actively destroy HIV-infected Helper T-cells to control the viral load. * **Carrier T-cells:** This is not a standard functional classification of T-cells in immunology. **High-Yield Clinical Pearls for NEET-PG:** * **Primary Receptor:** CD4 [1]. * **Co-receptors:** CCR5 (found on Macrophages/T-cells) and CXCR4 (found on T-cells) [1]. * **Other Target Cells:** Macrophages and Dendritic cells (act as reservoirs) and Microglial cells in the CNS. * **Marker of Progression:** A CD4 count below **200 cells/mm³** is the defining threshold for AIDS. * **Inversion of Ratio:** In HIV, the normal CD4:CD8 ratio (typically 2:1) is **inverted** (less than 1:1).

Question 790: Which of the following is a prion disease?

A. Creutzfeldt-Jacob disease (Correct Answer)
B. Subacute sclerosing panencephalitis
C. Alzheimer's disease
D. Parkinson disease

Explanation: **Explanation:** **Prion diseases**, also known as Transmissible Spongiform Encephalopathies (TSEs), are caused by **prions**—infectious proteinaceous particles that lack nucleic acids. They occur when the normal cellular protein ($PrP^C$) undergoes a conformational change into a misfolded, protease-resistant isoform ($PrP^{Sc}$). **Correct Option: A. Creutzfeldt-Jakob Disease (CJD)** CJD is the most common human prion disease. It is characterized by rapidly progressive dementia, myoclonus, and a "spongiform" appearance of the brain (vacuolation of neurons and gray matter) without inflammation. It can be sporadic (most common), familial, or acquired (variant CJD). **Incorrect Options:** * **B. Subacute Sclerosing Panencephalitis (SSPE):** This is a progressive neurological disorder caused by a persistent infection with a **defective Measles virus**, not a prion. It typically occurs years after the initial measles infection. * **C & D. Alzheimer’s and Parkinson’s Diseases:** While these are "protein-misfolding" neurodegenerative disorders (involving Amyloid-beta/Tau and Alpha-synuclein, respectively), they are **not** classified as infectious prion diseases or TSEs. **High-Yield Clinical Pearls for NEET-PG:** * **Diagnosis:** The presence of **14-3-3 protein** in CSF is a key biochemical marker for CJD. * **EEG Finding:** Characterized by **periodic sharp wave complexes (PSWCs)**. * **Kuru:** Another human prion disease associated with ritualistic cannibalism. * **Sterilization:** Prions are highly resistant; they require **autoclaving at 134°C** or immersion in **1N Sodium Hydroxide (NaOH)** for 1 hour for inactivation. Normal boiling or standard disinfectants are ineffective.

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Virology — MCQs

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