Virology — MCQs

In January, two school districts saw a sudden increase in absences. At the same time, sales of over-the-counter medications for fever, cough, and cold symptoms increased dramatically. To determine the etiology of this outbreak of respiratory illness, the public health department conducted a survey of local physicians to see what types of patients they were currently seeing most. The doctors all reported increased numbers of patients complaining of abrupt onset of high fever, severe headache, and myalgia followed by sore throat, dry cough, weakness, and severe fatigue. The patients were ill for 3 to 5 days, but many reported persistent malaise. What is the most likely diagnosis for this outbreak?

Q565Easy

Which one of the following is not a prion-associated disease?

Q566Easy

Which of the following viruses possesses DNA, a capsid with icosahedral symmetry and no lipid envelope?

Q567Easy

Phage typing is widely used for the intraspecies classification of which of the following bacteria?

Q568Medium

Which of the following viruses does not have an envelope containing hemagglutinin or neuraminidase?

Q569Easy

Varicella belongs to which family of virus?

Q570Easy

Erythema infectiosum is caused by which virus?

Virology Indian Medical PG Practice Questions and MCQs

Question 561: Varicella-zoster virus (VZV) is the cause of chickenpox and herpes zoster. Which of the following statements regarding VZV are true?

A. a,c, e are true; b,d are false
B. a,c,d,e are true; b is false (Correct Answer)
C. b,c,d,e are true; a is false
D. a,b,c,d,e are true; none are false

Explanation: **Explanation** Varicella-Zoster Virus (VZV), a member of the *Alphaherpesvirinae* subfamily (HHV-3), exhibits distinct clinical stages: primary infection (Chickenpox) and reactivation (Herpes Zoster). **Analysis of Statements:** * **(a) Primary infection causes Varicella (Chickenpox):** This is the initial generalized infection characterized by a centripetal, pleomorphic rash. * **(b) It remains latent in the B-cells:** **FALSE.** VZV remains latent in the **dorsal root ganglia** or cranial nerve ganglia. (Note: EBV is the herpesvirus that stays latent in B-cells). * **(c) Reactivation causes Herpes Zoster (Shingles):** Upon reactivation (due to age or immunosuppression), the virus travels down the sensory nerve to cause a painful, dermatomal vesicular rash. * **(d) Post-herpetic neuralgia is a complication:** This is the most common chronic complication of Shingles, characterized by persistent pain after the rash has healed. * **(e) Live attenuated vaccine is available:** The Oka strain is used for both the Varicella vaccine and the Zoster vaccine (though the Zoster vaccine uses a higher titer). **Why Option B is Correct:** Statements **a, c, d, and e** are scientifically accurate clinical and microbiological facts regarding VZV. Statement **b** is incorrect because VZV is neurotropic, not lymphotropic. **High-Yield NEET-PG Pearls:** * **Tzanck Smear:** Shows **Multinucleated Giant Cells** with Cowdry Type A intranuclear inclusion bodies (seen in VZV and HSV). * **Rash Progression:** "Dewdrop on a rose petal" appearance; hallmark is **pleomorphism** (all stages of rash—papule, vesicle, crust—seen simultaneously). * **Ramsay Hunt Syndrome:** Reactivation involving the geniculate ganglion (CN VII), leading to facial palsy and vesicles in the external auditory canal. * **Drug of Choice:** Oral Acyclovir (for adults/high-risk); Valacyclovir is preferred for Zoster due to better bioavailability.

Question 562: Epstein-Barr virus (EBV) enters B-cells through which receptor?

A. CD-1
B. CD-2
C. CD-21 (Correct Answer)
D. CD-19

Explanation: **Explanation:** **Correct Option: C (CD-21)** Epstein-Barr Virus (EBV), a member of the *Gammaherpesvirinae* subfamily, exhibits a specific tropism for B-lymphocytes. The virus utilizes its envelope glycoprotein **gp350/220** to bind to the **CD-21** receptor (also known as **CR2** or Complement Receptor type 2) found on the surface of mature B-cells. This interaction is the critical first step for viral entry and subsequent transformation of B-cells into immortalized lymphoblastoid cells. **Analysis of Incorrect Options:** * **A. CD-1:** These are MHC-like molecules involved in the presentation of lipid antigens to T-cells, not viral entry. * **B. CD-2:** This is an adhesion molecule found on T-cells and Natural Killer (NK) cells (also known as LFA-2); it is not the primary receptor for EBV. * **C. CD-19:** While CD-19 is a definitive marker for B-lineage cells and forms a complex with CD-21 to signal B-cell activation, it does not serve as the direct attachment site for EBV. **High-Yield Clinical Pearls for NEET-PG:** * **Infectious Mononucleosis (IM):** EBV is the primary cause. Diagnosis is supported by the presence of **Atypical Lymphocytes (Downey Cells)** on peripheral smear—these are actually activated **CD8+ T-cells** reacting against the infected B-cells. * **Malignancies:** EBV is strongly associated with Burkitt Lymphoma (t[8;14]), Nasopharyngeal Carcinoma, and Hodgkin Lymphoma. * **Diagnosis:** The **Paul-Bunnell Test** (Heterophile antibody test) is the classic screening tool. * **Receptor for Epithelial Cells:** While EBV uses CD-21 for B-cells, it uses **MHC Class II** molecules as a co-receptor and different integrins for entry into epithelial cells.

Question 563: Which of the following viruses is composed of two distinct capsids enclosing double-stranded RNA?

A. Adenovirus
B. Reovirus (Correct Answer)
C. Herpes virus
D. Myxovirus

Explanation: **Explanation:** The correct answer is **Reovirus**. **Why Reovirus is correct:** Reoviruses (e.g., Rotavirus) possess a unique architecture consisting of a **segmented, double-stranded RNA (dsRNA)** genome. Unlike most viruses, they are characterized by a complex **double-layered icosahedral capsid** (an inner and an outer capsid). This structure is essential for their replication cycle; the double capsid protects the dsRNA from triggering host cell-mediated interferon responses, as the genome is never fully "uncoated" into the cytoplasm. **Why the other options are incorrect:** * **Adenovirus:** These are non-enveloped viruses with a single icosahedral capsid containing **double-stranded DNA (dsDNA)**. * **Herpes virus:** These are enveloped viruses with a single icosahedral capsid containing **dsDNA**. They are noted for their "tegument" layer between the envelope and capsid. * **Myxovirus (Orthomyxovirus/Paramyxovirus):** These are enveloped viruses containing **single-stranded RNA (ssRNA)**. They do not possess a double capsid. **High-Yield Clinical Pearls for NEET-PG:** * **Rotavirus** (a Reovirus) is the most common cause of severe infantile diarrhea worldwide. * **Mnemonic for Reovirus:** "**RE**o" stands for **R**espiratory **E**nteric **O**rphan. * **Genome Fact:** Reoviruses and Birnaviruses are the only medically important viruses with **dsRNA**. * **Segmentation:** Rotavirus has **11 segments**, which allows for genetic reassortment (similar to Influenza). * **Appearance:** On electron microscopy, Rotavirus has a characteristic **"wheel-like"** appearance (Latin: *Rota* = wheel).

Question 564: In January, two school districts saw a sudden increase in absences. At the same time, sales of over-the-counter medications for fever, cough, and cold symptoms increased dramatically. To determine the etiology of this outbreak of respiratory illness, the public health department conducted a survey of local physicians to see what types of patients they were currently seeing most. The doctors all reported increased numbers of patients complaining of abrupt onset of high fever, severe headache, and myalgia followed by sore throat, dry cough, weakness, and severe fatigue. The patients were ill for 3 to 5 days, but many reported persistent malaise. What is the most likely diagnosis for this outbreak?

A. Common cold
B. Hand-foot-and-mouth disease
C. Influenza (Correct Answer)
D. Pharyngitis

Explanation: **Explanation:** The clinical presentation described is a classic textbook case of **Influenza**. The diagnosis is based on three key pillars: the **epidemiology** (sudden outbreak in winter/January, affecting school districts), the **abrupt onset**, and the **systemic nature** of the symptoms. 1. **Why Influenza is correct:** Unlike typical respiratory infections, Influenza is characterized by a sudden transition from health to high fever, severe myalgia (muscle aches), and headache. While respiratory symptoms like dry cough and sore throat are present, the profound systemic exhaustion (malaise and fatigue) that persists after the fever subsides is a hallmark of the Influenza virus. The timing (January) aligns with the peak flu season in the Northern Hemisphere. 2. **Why other options are incorrect:** * **Common Cold:** Usually caused by Rhinoviruses; it presents with gradual onset, prominent rhinorrhea (runny nose), and sneezing. High fever and severe myalgia are typically absent. * **Hand-foot-and-mouth disease:** Caused by Coxsackievirus A16; it presents with a characteristic vesicular rash on the palms, soles, and oral ulcers, rather than a primary severe respiratory/systemic syndrome. * **Pharyngitis:** While a component of many illnesses, primary bacterial pharyngitis (e.g., Strep throat) focuses on localized throat pain, tonsillar exudates, and cervical lymphadenopathy, without the widespread epidemic pattern or severe myalgia seen here. **High-Yield NEET-PG Pearls:** * **Antigenic Drift:** Point mutations in Hemagglutinin (HA) or Neuraminidase (NA) leading to seasonal epidemics (seen here). * **Antigenic Shift:** Genetic reassortment leading to pandemics (Influenza A only). * **Complication:** The most common complication is secondary bacterial pneumonia (often *S. pneumoniae* or *S. aureus*). * **Diagnosis:** Gold standard is RT-PCR; Rapid Influenza Diagnostic Tests (RIDTs) are common but have lower sensitivity.

Question 565: Which one of the following is not a prion-associated disease?

A. Scrapie
B. Kuru
C. Creutzfeldt-Jakob disease
D. Alzheimer's disease (Correct Answer)

Explanation: **Explanation:** Prions are proteinaceous infectious particles that lack nucleic acids. They cause **Transmissible Spongiform Encephalopathies (TSEs)**, characterized by the conversion of normal cellular prion protein ($PrP^C$) into an abnormal, protease-resistant misfolded form ($PrP^{Sc}$). **Why Alzheimer's Disease is the Correct Answer:** While Alzheimer’s disease involves protein misfolding (Amyloid-beta and Tau proteins), it is **not** classified as a prion disease. It is a neurodegenerative "tauopathy" or "amyloidosis." Unlike prion diseases, Alzheimer’s is not considered infectious or transmissible under natural conditions, and it does not produce the characteristic "spongiform" changes seen in TSEs. **Analysis of Incorrect Options:** * **A. Scrapie:** The prototypical prion disease affecting sheep and goats. It causes intense itching (leading animals to "scrape" against fences) and neurodegeneration. * **B. Kuru:** Historically found in the Fore tribe of Papua New Guinea, transmitted through ritualistic cannibalism. It is the first human prion disease demonstrated to be transmissible. * **C. Creutzfeldt-Jakob disease (CJD):** The most common human prion disease. It presents as rapidly progressive dementia with myoclonus and characteristic periodic sharp wave complexes on EEG. **High-Yield Clinical Pearls for NEET-PG:** 1. **Resistance:** Prions are highly resistant to standard sterilization (autoclaving, UV light, and formalin). They require **sodium hydroxide (1N NaOH)** or extended autoclaving at **134°C**. 2. **Diagnosis:** The presence of **14-3-3 protein** in CSF is a significant marker for CJD. 3. **Pathology:** Histology shows "spongiform" vacuolation of neurons and astrocytes without any inflammatory response (no pleocytosis). 4. **Variant CJD (vCJD):** Linked to the consumption of beef infected with Bovine Spongiform Encephalopathy (Mad Cow Disease).

Question 566: Which of the following viruses possesses DNA, a capsid with icosahedral symmetry and no lipid envelope?

A. Herpesvirus
B. Adenovirus (Correct Answer)
C. Poxvirus
D. Papovavirus

Explanation: To answer this question, one must recall the structural classification of DNA viruses based on their envelope and symmetry. ### **Explanation** **Adenovirus** is the correct answer because it fits all three criteria: it has a **double-stranded DNA** genome, a **naked (non-enveloped)** nucleocapsid, and **icosahedral symmetry**. It is uniquely characterized by "penton fibers" (spikes) protruding from the vertices of the icosahedron, which aid in attachment. ### **Analysis of Incorrect Options** * **Herpesvirus (A):** While it has a DNA genome and icosahedral symmetry, it is a **highly enveloped** virus. The envelope is derived from the host's nuclear membrane. * **Poxvirus (C):** This is the "exception" among DNA viruses. It is the largest DNA virus and possesses **complex symmetry** (brick-shaped) rather than icosahedral. It is also **enveloped**. * **Papovavirus (D):** This group (including Papilloma and Polyoma viruses) is indeed DNA-based, icosahedral, and naked. However, in modern taxonomy, "Papovavirus" is an obsolete term. **Adenovirus** is the more classic and frequently tested representative for this structural profile in NEET-PG, often distinguished by its specific clinical presentations. ### **High-Yield Clinical Pearls for NEET-PG** * **DNA Virus Rule:** All DNA viruses are double-stranded (except **Parvovirus**) and all are icosahedral (except **Poxvirus**). * **Enveloped DNA Viruses:** Remember the mnemonic **"He He Po"** (Herpes, Hepadna, Pox). All others are naked. * **Adenovirus Clinical Links:** It is a common cause of **Pharyngoconjunctival fever**, **Epidemic keratoconjunctivitis** (Pink eye), and **Hemorrhagic cystitis** (Types 11, 21). * **Intranuclear Inclusions:** Adenovirus produces "Smudge cells" (basophilic intranuclear inclusions).

Question 567: Phage typing is widely used for the intraspecies classification of which of the following bacteria?

A. Staphylococci (Correct Answer)
B. E. coli
C. Klebsiella pneumoniae
D. Pseudomonas aeruginosa

Explanation: **Explanation:** **Phage typing** is a method used for the epidemiological surveillance and intraspecies classification of bacteria based on their susceptibility to specific bacteriophages. **Why Staphylococci is correct:** *Staphylococcus aureus* is the classic organism for which phage typing is the "gold standard" for strain differentiation. It is primarily used to trace the source of hospital-acquired outbreaks (nosocomial infections). The International Reference Center for Staphylococcal Phage Typing has established a standardized set of 22 phages (divided into four groups) to identify specific patterns or "phage types" of *S. aureus*. **Why other options are incorrect:** * **E. coli:** While phage typing exists for certain strains (like O157:H7), it is not the primary method for intraspecies classification. Serotyping (O and H antigens) and molecular methods (MLST) are more commonly used. * **Klebsiella pneumoniae:** Classification is predominantly done via **Capsular (K) typing** and **Bacteriocin typing**. * **Pseudomonas aeruginosa:** While phage typing is possible, **Pyocin typing** (bacteriocin typing) is the more traditional and widely recognized method for intraspecies differentiation of this organism. **High-Yield Clinical Pearls for NEET-PG:** * **Bacteriocin Typing:** Most commonly used for *Pseudomonas aeruginosa* (Pyocin) and *Shigella sonnei* (Colicin). * **Vi-phage typing:** Specifically used for *Salmonella Typhi* to track typhoid fever outbreaks. * **Modern Trend:** Phage typing is being rapidly replaced by molecular methods like **PFGE (Pulsed-field gel electrophoresis)** and **Whole Genome Sequencing (WGS)**, which offer higher discriminatory power.

Question 568: Which of the following viruses does not have an envelope containing hemagglutinin or neuraminidase?

A. Mumps
B. Parainfluenza
C. Respiratory syncytial virus (Correct Answer)
D. Measles virus

Explanation: **Explanation:** The question tests your knowledge of the surface glycoproteins of the **Paramyxoviridae** family. All members of this family possess two types of glycoprotein spikes on their envelope: a **Fusion (F) protein** (responsible for cell-to-cell fusion and syncytia formation) and an **Attachment protein**. **Why C is correct:** **Respiratory Syncytial Virus (RSV)** is unique among the Paramyxoviruses because its attachment protein (the **G protein**) lacks both Hemagglutinin (H) and Neuraminidase (N) activity. While it possesses the F protein (hence the name "Syncytial"), it does not agglutinate red blood cells or cleave sialic acid. **Why the other options are incorrect:** * **Mumps and Parainfluenza (A & B):** These viruses possess a combined **HN protein**, which exhibits both Hemagglutinin and Neuraminidase activities. * **Measles (D):** The Measles virus possesses an **H protein** (Hemagglutinin activity) but lacks Neuraminidase (N) activity. **NEET-PG High-Yield Pearls:** 1. **RSV:** It is the most common cause of **bronchiolitis** and pneumonia in infants. It lacks HN activity but has a G protein for attachment. 2. **Palivizumab:** A monoclonal antibody used for RSV prophylaxis; it targets the **F protein**. 3. **Paramyxoviridae Summary:** * **Mumps/Parainfluenza:** Have both H and N (HN protein). * **Measles:** Has H, but No N. * **RSV:** Has neither H nor N (G protein). * **All:** Possess the F (Fusion) protein. 4. **Inclusion Bodies:** Measles produces both intracytoplasmic and intranuclear inclusion bodies (Warthin-Finkeldey cells).

Question 569: Varicella belongs to which family of virus?

A. Adeniviridae
B. Paxviridae
C. Papovaviridae
D. Herpesviridae (Correct Answer)

Explanation: ### Explanation **Correct Answer: D. Herpesviridae** Varicella-Zoster Virus (VZV) is a member of the **Herpesviridae** family, specifically belonging to the **Alphaherpesvirinae** subfamily. It is a large, enveloped virus with a linear double-stranded DNA (dsDNA) genome and an icosahedral capsid. VZV is the causative agent of two distinct clinical entities: **Chickenpox (Varicella)** during primary infection and **Shingles (Herpes Zoster)** upon reactivation from latency in the dorsal root ganglia. **Why the other options are incorrect:** * **Adenoviridae:** These are non-enveloped dsDNA viruses. They typically cause respiratory infections (pharyngitis), conjunctivitis (pink eye), and gastroenteritis, but do not cause vesicular rashes like Varicella. * **Poxviridae (misspelled as Paxviridae):** While Poxviruses (like Variola/Smallpox and Molluscum contagiosum) also cause skin lesions, they are the largest DNA viruses and replicate in the **cytoplasm**, unlike Herpesviruses which replicate in the nucleus. * **Papovaviridae:** This is an older taxonomic term now split into *Papillomaviridae* (HPV) and *Polyomaviridae* (BK/JC virus). These are small, non-enveloped circular dsDNA viruses associated with warts and malignancies, not acute vesicular eruptions. **Clinical Pearls for NEET-PG:** * **Latency:** Like all Herpesviruses, VZV establishes lifelong latency (specifically in sensory nerve ganglia). * **Tzanck Smear:** Microscopic examination of vesicle fluid shows **Multinucleated Giant Cells** with Cowdry Type A intranuclear inclusion bodies (characteristic of Herpesviridae). * **Vaccine:** The Varicella vaccine is a **live-attenuated** strain (Oka strain). * **Congenital Varicella Syndrome:** Characterized by cicatricial skin scarring, limb hypoplasia, and chorioretinitis if the mother is infected during early pregnancy.

Question 570: Erythema infectiosum is caused by which virus?

A. Parvovirus B19 (Correct Answer)
B. JC virus
C. Rotavirus
D. Mumps

Explanation: **Explanation:** **Erythema Infectiosum**, also known as **Fifth Disease**, is a common childhood exanthem caused by **Parvovirus B19**. This virus is a small, non-enveloped, single-stranded DNA virus. It specifically targets and replicates in erythroid progenitor cells (proerythroblasts) by binding to the **P-antigen** (globoside) on the cell surface. The characteristic clinical presentation is a "slapped-cheek" rash on the face, followed by a reticular, lace-like erythematous rash on the trunk and extremities. **Analysis of Options:** * **B. JC Virus:** A polyomavirus that causes Progressive Multifocal Leukoencephalopathy (PML), a demyelinating disease of the CNS, typically in immunocompromised patients. * **C. Rotavirus:** The most common cause of severe dehydrating diarrhea in infants and young children worldwide. * **D. Mumps:** A paramyxovirus characterized by painful swelling of the parotid glands (parotitis) and potential complications like orchitis or meningitis. **High-Yield Clinical Pearls for NEET-PG:** * **Aplastic Crisis:** Parvovirus B19 can cause a transient cessation of erythropoiesis. This is life-threatening in patients with high red cell turnover (e.g., Sickle Cell Anemia, Hereditary Spherocytosis). * **Hydrops Fetalis:** If a pregnant woman is infected, the virus can cross the placenta, leading to severe fetal anemia, high-output cardiac failure, and fetal death. * **Arthropathy:** In adults (especially females), infection often presents as symmetrical small joint arthritis resembling rheumatoid arthritis. * **Pure Red Cell Aplasia (PRCA):** Seen in immunocompromised individuals due to chronic B19 infection.

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Virology — MCQs

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