Virology — MCQs
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A 43-year-old executive presents with chronic symmetric polyarthritis involving the knees. He has a history of an extensive rash after a deer-hunting trip several years earlier, accompanied by 'sick' feeling and knee pain that partially resolved after several months. Which of the following organisms is most likely etiologically related to the patient's arthritis?
Hemagglutinin and neuraminidase are found in which virus?
What is true about Congenital Rubella Syndrome?
Which of the following conditions is caused by Adenovirus?
Which of the following enzymes does HIV contain?
What is the most sensitive test for the diagnosis of herpes simplex (HSV) encephalitis?
Which of the following is a known reservoir for the Ebola virus?
Which of the following viruses is not included in the Picornaviridae family?
Which of the following statements about the virus described is/are true? The virus is enveloped, has club or petal shaped projections, and possesses a positive-sense single-stranded RNA genome with the largest genome among RNA viruses. Diseases caused by these viruses include SARS and MERS. The reservoir for SARS is horseshoe bats, with likely spread from palm civets and cats to humans. Symptoms of MERS appear within a day following contact with an infected patient. SARS is more severe than MERS. MERS infection is more severe in individuals with pre-existing illnesses like diabetes and heart diseases.
What is the most sensitive investigation for the diagnosis of asymptomatic Chlamydial infection?
Virology Indian Medical PG Practice Questions and MCQs
Question 81: A 43-year-old executive presents with chronic symmetric polyarthritis involving the knees. He has a history of an extensive rash after a deer-hunting trip several years earlier, accompanied by 'sick' feeling and knee pain that partially resolved after several months. Which of the following organisms is most likely etiologically related to the patient's arthritis?
- A. Fungus
- B. Gram-negative cocci
- C. Gram-positive cocci
- D. Spirochete (Correct Answer)
Explanation: ### Explanation The clinical presentation describes a classic case of **Lyme Disease**, caused by the spirochete ***Borrelia burgdorferi***. **1. Why the Correct Answer is Right:** The patient’s history of a deer-hunting trip (exposure to *Ixodes* ticks) followed by an "extensive rash" (likely **Erythema Chronicum Migrans**) and systemic "sick" feelings points to Stage 1 and 2 of Lyme disease. The current presentation of chronic symmetric polyarthritis (specifically involving the knees) represents **Stage 3 (Late Disseminated) Lyme disease**. *Borrelia burgdorferi* is a **spirochete**, which is the causative agent. **2. Why the Incorrect Options are Wrong:** * **Fungus (Option A):** While some fungi (like *Coccidioides*) can cause joint pain, they typically present with pulmonary symptoms and are not associated with a preceding migratory rash or deer-tick exposure. * **Gram-negative cocci (Option B):** *Neisseria gonorrhoeae* is a common cause of septic arthritis in adults. However, it usually presents as an acute, migratory tenosynovitis or a monoarthritis, often with urogenital symptoms, rather than a chronic condition following a rash years later. * **Gram-positive cocci (Option C):** *Staphylococcus aureus* and *Streptococcus* species are the leading causes of acute bacterial (septic) arthritis. These cause rapid joint destruction and high fever, not a chronic, relapsing-remitting course over several years. **3. High-Yield Clinical Pearls for NEET-PG:** * **Vector:** *Ixodes* tick (also transmits Babesia and Anaplasma). * **Natural Reservoir:** White-footed mouse (larvae); White-tailed deer (adult ticks). * **Stages:** * **Stage 1:** Erythema Migrans (Bull’s eye rash), flu-like symptoms. * **Stage 2:** Early disseminated (Bilateral Bell’s palsy, AV block). * **Stage 3:** Late disseminated (Chronic arthritis of large joints, encephalopathy). * **Treatment:** Doxycycline (early); Ceftriaxone (late/disseminated).
Question 82: Hemagglutinin and neuraminidase are found in which virus?
- A. Norovirus
- B. Hantavirus
- C. Influenza virus (Correct Answer)
- D. Rubella virus
Explanation: **Explanation:** The **Influenza virus** (Orthomyxoviridae family) is characterized by two major surface glycoproteins: **Hemagglutinin (HA)** and **Neuraminidase (NA)**. * **Hemagglutinin (HA):** Responsible for binding the virus to sialic acid receptors on host cells and facilitating membrane fusion (entry). It is the primary target for neutralizing antibodies. * **Neuraminidase (NA):** An enzyme that cleaves sialic acid residues, allowing the release of newly formed virions from the host cell (exit) and preventing viral aggregation. **Analysis of Incorrect Options:** * **Norovirus:** A non-enveloped, positive-sense RNA virus (Caliciviridae) known for causing epidemic gastroenteritis. It lacks an envelope and these specific surface spikes. * **Hantavirus:** Part of the Bunyaviridae family. While it has surface glycoproteins (Gn and Gc), it does not possess HA or NA. It is typically transmitted via rodent excreta (causing HFRS or HPS). * **Rubella virus:** A Togavirus that possesses HA activity (used in the Hemagglutination Inhibition test), but it **lacks Neuraminidase**. **High-Yield Clinical Pearls for NEET-PG:** * **Antigenic Drift:** Minor point mutations in HA/NA leading to seasonal epidemics. * **Antigenic Shift:** Major genetic reassortment (only in Influenza A) leading to pandemics. * **Drug Link:** **Oseltamivir** and **Zanamivir** are Neuraminidase inhibitors that prevent the release of the virus from infected cells. * **Cultivation:** Influenza virus is classically grown in the **amniotic cavity** of embryonated chicken eggs.
Question 83: What is true about Congenital Rubella Syndrome?
- A. It can result in a chronic infection. (Correct Answer)
- B. The virus can be isolated up to 6 months after birth.
- C. The classic triad of CRS includes cataracts, cardiac defects, and hearing loss.
- D. Congenital Rubella infection is most serious during the first trimester of pregnancy.
Explanation: **Congenital Rubella Syndrome (CRS)** occurs when the Rubella virus crosses the placenta during maternal viremia. **Explanation of the Correct Option:** **Option A** is correct because CRS is characterized by a **chronic, persistent infection**. Unlike postnatal rubella, which is self-limiting, the fetus cannot effectively clear the virus due to an immature immune system. The virus persists in tissues (like the lens of the eye) and is shed in secretions for a prolonged period after birth. **Analysis of Other Options:** * **Option B is incorrect** because the virus can be isolated for much longer than 6 months. Infants with CRS can shed the virus in nasopharyngeal secretions and urine for **up to 1 year or more**, posing a risk to susceptible healthcare workers. * **Option C is incorrect** because while it describes the "Gregg’s Triad," the question asks for what is *true* regarding the nature of the infection. However, in many standardized exams, if multiple statements are technically true, the most definitive biological characteristic (chronic persistence) is prioritized. *Note: In many clinical contexts, C and D are also true; however, in the context of this specific question's key, the focus is on the chronic nature of the viral shedding.* * **Option D is incorrect** only in the context of this specific single-best-answer key; clinically, the risk of malformation is indeed highest (up to 85%) during the **first trimester**. **High-Yield NEET-PG Pearls:** * **Classic Triad (Gregg’s Triad):** Cataracts ("Pearls in the eye"), Sensorineural hearing loss (most common), and Cardiac defects (PDA is most common; Pulmonary artery stenosis). * **Other signs:** "Blueberry muffin" rash (extramedullary hematopoiesis) and radiolucent bone lesions ("Celery stalking"). * **Diagnosis:** Detection of **Rubella-specific IgM** in the newborn or persistence of IgG beyond 6–12 months. * **Prevention:** Live attenuated **RA 27/3 strain** vaccine. It is contraindicated in pregnancy; women should avoid pregnancy for 1 month after vaccination.
Question 84: Which of the following conditions is caused by Adenovirus?
- A. Keratoconjunctivitis (Correct Answer)
- B. Diarrhea
- C. Parotid enlargement
- D. All of the above
Explanation: **Explanation:** Adenoviruses are non-enveloped, double-stranded DNA viruses known for their diverse tissue tropism, primarily affecting the respiratory, ocular, and gastrointestinal systems. 1. **Why Keratoconjunctivitis is Correct:** Adenovirus is the most common cause of viral conjunctivitis. Specifically, **Epidemic Keratoconjunctivitis (EKC)**, caused by serotypes 8, 19, and 37, is a severe condition characterized by "pink eye" followed by corneal involvement (keratitis) and preauricular lymphadenopathy. It is highly contagious and often occurs in clusters. 2. **Analysis of Other Options:** * **Diarrhea:** While Adenovirus (serotypes 40 and 41) is a significant cause of infantile gastroenteritis, it is generally considered the second most common viral cause after Rotavirus. In the context of standard medical examinations, if a single best answer is required and Keratoconjunctivitis is listed, it is the classic "textbook" association for Adenovirus. * **Parotid Enlargement:** This is the hallmark of the **Mumps virus** (a Paramyxovirus), not Adenovirus. * **All of the Above:** Since parotid enlargement is not associated with Adenovirus, this option is incorrect. **High-Yield Clinical Pearls for NEET-PG:** * **Pharyngoconjunctival Fever:** Caused by serotypes 3 and 7; characterized by the triad of fever, pharyngitis, and follicular conjunctivitis (often associated with swimming pools). * **Hemorrhagic Cystitis:** Adenovirus serotypes 11 and 21 are classic causes of acute hemorrhagic cystitis in children and bone marrow transplant recipients. * **Intussusception:** Adenoviral infection can lead to Peyer’s patch hypertrophy, acting as a lead point for intussusception in infants. * **Structure:** It possesses a unique **penton fiber** that projects from the capsid, which acts as a hemagglutinin and is toxic to human cells.
Question 85: Which of the following enzymes does HIV contain?
- A. Integrase
- B. RNA directed DNA polymerase
- C. Ribonuclease
- D. All of the above (Correct Answer)
Explanation: **Explanation:** HIV (Human Immunodeficiency Virus) is a member of the *Lentivirus* genus within the **Retroviridae** family. As a retrovirus, it carries a unique enzymatic machinery within its nucleocapsid core that is essential for its replication cycle, specifically for converting its RNA genome into DNA and integrating it into the host genome. * **RNA-directed DNA polymerase (Reverse Transcriptase):** This is the hallmark enzyme of HIV. It transcribes the viral single-stranded RNA into double-stranded DNA. It possesses three activities: RNA-dependent DNA polymerase, DNA-dependent DNA polymerase, and Ribonuclease H. * **Ribonuclease (RNase H):** This enzyme is a specific subunit/activity of the Reverse Transcriptase complex. Its crucial role is to degrade the original viral RNA strand from the RNA-DNA hybrid intermediate, allowing the synthesis of the second DNA strand. * **Integrase (p32):** Once the viral DNA is synthesized, Integrase facilitates its transport into the host nucleus and catalyzes the "integration" of viral DNA into the host cell chromosome, forming a **provirus**. Since HIV requires all three enzymes (Reverse Transcriptase, RNase H, and Integrase) along with **Protease** (for viral maturation) to complete its life cycle, **Option D** is the correct answer. **High-Yield Clinical Pearls for NEET-PG:** 1. **Gene Coding:** *Pol* gene codes for all three enzymes: Protease (p10), Reverse Transcriptase (p66/51), and Integrase (p32). 2. **Drug Targets:** * **NRTIs/NNRTIs** (e.g., Zidovudine, Efavirenz) target Reverse Transcriptase. * **INSTIs** (e.g., Raltegravir, Dolutegravir) target Integrase. * **PIs** (e.g., Ritonavir) target Protease. 3. **Diagnostic Marker:** p24 is the major core antigen used for early diagnosis (fourth-generation ELISA).
Question 86: What is the most sensitive test for the diagnosis of herpes simplex (HSV) encephalitis?
- A. Cerebrospinal fluid (CSF) protein analysis
- B. HSV culture
- C. HSV IgG antibody
- D. HSV polymerase chain reaction (Correct Answer)
Explanation: **Explanation:** **HSV Polymerase Chain Reaction (PCR)** is the gold standard and the most sensitive test for diagnosing HSV encephalitis (HSE). It detects viral DNA in the cerebrospinal fluid (CSF) with a sensitivity and specificity exceeding 95%. In clinical practice, PCR has replaced brain biopsy as the definitive diagnostic tool because it is non-invasive and provides rapid results during the acute phase of the illness. **Analysis of Incorrect Options:** * **CSF Protein Analysis:** While CSF protein is often elevated in HSE, this is a non-specific finding seen in various inflammatory, infectious, and neoplastic conditions of the CNS. It cannot differentiate HSV from other causes of encephalitis. * **HSV Culture:** Viral culture of the CSF is notoriously insensitive for HSV-1 (the primary cause of adult HSE), as the virus rarely replicates in the subarachnoid space in detectable quantities. * **HSV IgG Antibody:** IgG indicates past exposure, not acute infection. While a four-fold rise in antibody titers or intrathecal antibody production can confirm HSE, these changes occur late (after 10–14 days), making them useless for acute diagnosis and management. **High-Yield Clinical Pearls for NEET-PG:** * **Etiology:** HSV-1 is the most common cause of sporadic fatal encephalitis in adults; HSV-2 is more common in neonates (via birth canal). * **Localization:** HSE characteristically involves the **temporal lobes** (look for hemorrhagic necrosis on imaging). * **EEG Finding:** Periodic lateralizing epileptiform discharges (PLEDs) are highly suggestive. * **Treatment:** Start **Intravenous Acyclovir** empirically as soon as HSE is suspected, even before PCR results are available.
Question 87: Which of the following is a known reservoir for the Ebola virus?
- A. Japanese encephalitis virus
- B. Ebola virus (Correct Answer)
- C. Zika virus
- D. Plasmodium falciparum
Explanation: **Explanation:** The **Ebola virus**, a member of the *Filoviridae* family, causes severe hemorrhagic fever. In the context of its natural life cycle, the primary reservoir is believed to be **fruit bats** (specifically genera *Hypsignathus monstrosus*, *Epomops franqueti*, and *Myonycteris torquata*). The virus is transmitted to humans through contact with infected bushmeat (monkeys, forest antelope) or directly via bat excreta. *Note: The question structure provided implies a self-referential identification; however, in a clinical sense, the "reservoir" refers to the ecological niche where the pathogen survives.* **Analysis of Options:** * **Option A (Japanese Encephalitis Virus):** This is a Flavivirus. Its natural reservoir is **pigs and water birds** (like herons and egrets), and it is transmitted to humans via the *Culex* mosquito. * **Option C (Zika Virus):** Another Flavivirus. While it primarily circulates between humans and *Aedes* mosquitoes, its sylvatic (jungle) reservoir involves **non-human primates**. * **Option D (Plasmodium falciparum):** This is a protozoan parasite, not a virus. Its primary reservoir and definitive host is the **female Anopheles mosquito**, while humans serve as intermediate hosts. **High-Yield Clinical Pearls for NEET-PG:** * **Transmission:** Human-to-human spread occurs through direct contact with **broken skin or mucous membranes** and bodily fluids (blood, vomit, feces). * **Pathogenesis:** Ebola causes "cytokine storm" and severe DIC (Disseminated Intravascular Coagulation). * **Diagnosis:** RT-PCR is the gold standard during the acute phase; ELISA for IgM/IgG is used later. * **Biosafety Level:** Ebola requires **BSL-4** containment, the highest level of laboratory security.
Question 88: Which of the following viruses is not included in the Picornaviridae family?
- A. Rhinovirus
- B. Hepatitis E Virus (HEV) (Correct Answer)
- C. Hepatitis A Virus (HAV)
- D. Poliovirus
Explanation: **Explanation:** The **Picornaviridae** family consists of small (pico), non-enveloped, positive-sense single-stranded RNA (+ssRNA) viruses with icosahedral symmetry. **Why Hepatitis E Virus (HEV) is the correct answer:** Hepatitis E Virus was previously classified under Picornaviridae due to its similar morphology. However, it is now classified in its own family, **Hepeviridae** (Genus: *Orthohepevirus*). While it is a non-enveloped +ssRNA virus like picornaviruses, its genomic organization and replication strategy are distinct. **Why the other options are incorrect:** * **Rhinovirus:** A classic member of the Picornaviridae family. It is the most common cause of the common cold and is acid-labile (unlike other enteroviruses). * **Hepatitis A Virus (HAV):** Formerly known as Enterovirus 72, it is a member of the **Hepatovirus** genus within the Picornaviridae family. It is acid-stable and transmitted via the fecal-oral route. * **Poliovirus:** A member of the **Enterovirus** genus within Picornaviridae. It is a highly infectious virus that targets the anterior horn cells of the spinal cord. **NEET-PG High-Yield Pearls:** * **Picornaviridae Mnemonic (PERCH):** **P**oliovirus, **E**cho virus, **R**hinovirus, **C**oxsackievirus, **H**epatitis A virus. * **HEV & Pregnancy:** HEV infection in pregnant women (especially in the 3rd trimester) carries a high mortality rate (up to 20%) due to fulminant hepatic failure. * **Naked RNA:** The RNA of Picornaviruses is infectious by itself because it can act directly as mRNA upon entering the host cell.
Question 89: Which of the following statements about the virus described is/are true? The virus is enveloped, has club or petal shaped projections, and possesses a positive-sense single-stranded RNA genome with the largest genome among RNA viruses. Diseases caused by these viruses include SARS and MERS. The reservoir for SARS is horseshoe bats, with likely spread from palm civets and cats to humans. Symptoms of MERS appear within a day following contact with an infected patient. SARS is more severe than MERS. MERS infection is more severe in individuals with pre-existing illnesses like diabetes and heart diseases.
- A. The statement regarding enveloped nature, projections, genome type, SARS/MERS causation, reservoir, and SARS severity is true.
- B. The statement regarding enveloped nature, projections, genome type, SARS/MERS causation, and reservoir is true.
- C. The statement regarding enveloped nature, projections, genome type, SARS/MERS causation, and MERS severity in those with pre-existing illness is true. (Correct Answer)
- D. All the presented statements are true.
Explanation: The question describes **Coronaviruses**, which are characterized by their large, positive-sense ssRNA genome (approx. 30 kb), enveloped structure, and distinctive "club-shaped" spikes (peplomers). ### Why Option C is Correct * **Morphology & Genome:** Coronaviruses are indeed enveloped with petal-shaped projections and possess the largest RNA genome. * **Pathogenesis:** They cause SARS (SARS-CoV) and MERS (MERS-CoV). * **Risk Factors:** MERS-CoV is known to cause significantly more severe disease and higher mortality in patients with comorbidities such as **diabetes, renal failure, and chronic heart disease**. ### Why Other Options are Incorrect * **Incubation Period:** The statement that MERS symptoms appear "within a day" is false. The incubation period for MERS is typically **2 to 14 days**. * **Comparative Severity:** The statement that SARS is more severe than MERS is false. MERS has a much higher case fatality rate (**~35%**) compared to SARS (**~10%**). * **Reservoirs:** While horseshoe bats are the natural reservoir for SARS, the primary intermediate host for MERS is the **dromedary camel**, not civet cats. ### High-Yield NEET-PG Pearls * **Replication:** Unlike most RNA viruses, Coronaviruses have a **"proofreading" mechanism** (Exonuclease Nsp14), which explains how they maintain such a large genome without lethal mutations. * **Receptor Binding:** * **SARS-CoV & SARS-CoV-2:** Bind to **ACE2** receptors. * **MERS-CoV:** Binds to **DPP-4** (CD26) receptors. * **Diagnosis:** RT-PCR is the gold standard for acute infection.
Question 90: What is the most sensitive investigation for the diagnosis of asymptomatic Chlamydial infection?
- A. Ligase Chain Reaction (Correct Answer)
- B. Serodiagnosis
- C. Iodine Staining
- D. Culture
Explanation: **Explanation:** **Ligase Chain Reaction (LCR)** is a type of **Nucleic Acid Amplification Test (NAAT)**. In asymptomatic Chlamydial infections, the bacterial load is often extremely low, making traditional methods unreliable. NAATs (like LCR and PCR) are considered the "Gold Standard" for screening because they amplify specific DNA sequences, allowing for the detection of minute quantities of *Chlamydia trachomatis*. They are highly sensitive (>90-95%) and can be performed on non-invasive samples like first-void urine or vaginal swabs. **Why other options are incorrect:** * **Culture:** While historically the "legal gold standard" due to 100% specificity, it is technically demanding, expensive, and has low sensitivity (50-80%), especially in asymptomatic cases where viable organism count is low. * **Iodine Staining:** This method detects glycogen-containing inclusion bodies (Halberstaedter-Prowazek bodies) under light microscopy. It is specific but has very poor sensitivity and is not suitable for screening asymptomatic patients. * **Serodiagnosis:** Detection of antibodies (IgM/IgG) is generally unhelpful for acute genital infections because it cannot distinguish between a current infection and a past exposure. It is primarily used for diagnosing Lymphogranuloma Venereum (LGV) or neonatal pneumonia. **High-Yield Clinical Pearls for NEET-PG:** * **NAAT** is the investigation of choice for both symptomatic and asymptomatic Chlamydia. * **Sample of choice:** First-void urine (men) and vaginal swabs (women). * *Chlamydia trachomatis* is an **obligate intracellular** bacterium; it cannot be grown on artificial media and requires cell lines like **McCoy, HeLa, or BHK-21**. * **Treatment of choice:** Azithromycin (1g single dose) or Doxycycline (100mg BID for 7 days).
Practice by Chapter
Virus Structure and Classification
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Viral Replication
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Pathogenesis of Viral Infections
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DNA Viruses: Herpesviruses
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DNA Viruses: Poxviruses and Adenoviruses
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Hepatitis Viruses
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RNA Viruses: Orthomyxoviruses
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RNA Viruses: Paramyxoviruses
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Enteroviruses and Rhinoviruses
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Arboviruses
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HIV and Retroviruses
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Oncogenic Viruses
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