Virology — MCQs
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Which of the following statements about p24 is false?
Which of the following is an enveloped virus?
Pharyngeal-conjunctival fever is caused by
What indicates HBV replication?
Which additional gene is present in the Human T-cell Leukemia Virus (HTLV)?
All are true regarding mumps, EXCEPT:
Reverse transcriptase is a RNA-dependent DNA polymerase. Which of the following uses it?
Which virus is most commonly recognized as a prototypical viral hemorrhagic fever in endemic regions of West Africa?
Active replication in hepatitis B infection is indicated by:
Which of the following is NOT a poxvirus?
Virology Indian Medical PG Practice Questions and MCQs
Question 1371: Which of the following statements about p24 is false?
- A. Cannot be detected after seroconversion (Correct Answer)
- B. Cannot be seen in the first week
- C. All of the above
- D. Can be detected after 3 weeks of infection
Explanation: ***Cannot be detected after seroconversion*** - This statement is **FALSE** and is the correct answer to this question. - **p24 antigen levels do decrease** after seroconversion due to immune complex formation with antibodies, but p24 can still be detected using modern assays. - In **advanced HIV disease** with declining CD4 counts, p24 antigen often becomes detectable again due to high viral loads. - Fourth-generation HIV tests detect both antibodies and p24 antigen throughout the infection course. *Cannot be seen in the first week* - This statement is **TRUE** (not the answer). - p24 antigen typically appears around **10-14 days** (1.5-2 weeks) after infection, which is after the first week (days 1-7). - The eclipse period (first 7-10 days) precedes p24 detection. *Can be detected after 3 weeks of infection* - This statement is **TRUE** (not the answer). - p24 antigen is consistently detectable at 3 weeks post-infection during the acute viremic phase. - Peak p24 levels occur around **2-4 weeks** after infection. *All of the above* - This is a distractor option and is incorrect since only one statement is false.
Question 1372: Which of the following is an enveloped virus?
- A. Dengue virus (Correct Answer)
- B. Norwalk virus
- C. Hep A virus
- D. Adenovirus
Explanation: ***Dengue virus*** - The **Dengue virus** is a member of the **Flaviviridae** family, which are known to be **enveloped viruses**. - Its outer lipid envelope, derived from the host cell, is crucial for its entry into host cells and evading the immune system. *Norwalk virus* - The **Norwalk virus**, also known as **Norovirus**, is a **non-enveloped RNA virus** belonging to the **Caliciviridae** family. - Its lack of an envelope makes it more resistant to disinfectants and environmental stresses, contributing to its high infectivity and ability to cause outbreaks of gastroenteritis. *Hep A virus* - **Hepatitis A virus (HAV)** is a **non-enveloped RNA virus** of the **Picornaviridae** family. - Its non-enveloped nature contributes to its stability in the environment and resistance to gastric acid, facilitating its fecal-oral transmission. *Adenovirus* - **Adenoviruses** are **non-enveloped DNA viruses** known for causing a variety of clinical manifestations, including respiratory infections, conjunctivitis, and gastroenteritis. - Their lack of an outer lipid envelope helps them survive in harsh environmental conditions and makes them highly stable.
Question 1373: Pharyngeal-conjunctival fever is caused by
- A. Adenovirus 3 and 7 (Correct Answer)
- B. Adenovirus 11, 21
- C. Adenovirus 40, 41
- D. Adenovirus 8, 19
Explanation: ***Adenovirus 3 and 7*** - **Adenovirus serotypes 3 and 7** are the most common causes of **pharyngoconjunctival fever**, which presents with combination of **pharyngitis**, **conjunctivitis**, and **fever**. - This syndrome often occurs in outbreaks, particularly in children, and can be spread through **respiratory droplets** or contaminated water. *Adenovirus 11, 21* - **Adenovirus 11 and 21** are primarily associated with **hemorrhagic cystitis**, an inflammation of the bladder often presenting with **hematuria**. - They are less commonly implicated in typical pharyngoconjunctival fever, though adenoviruses can cause a spectrum of respiratory symptoms. *Adenovirus 40, 41* - **Adenovirus serotypes 40 and 41** are leading causes of **infantile gastroenteritis**, characterized by **diarrhea** and **vomiting**. - They are not typically associated with respiratory or ocular manifestations like pharyngoconjunctival fever. *Adenovirus 8, 19* - **Adenovirus 8 and 19** are well-known causes of **epidemic keratoconjunctivitis**, a severe form of conjunctivitis often involving the **cornea**. - While they cause a significant eye infection, they are not the primary serotypes linked to the broader syndrome of **pharyngoconjunctival fever** which includes pharyngitis and fever.
Question 1374: What indicates HBV replication?
- A. HBV DNA (Correct Answer)
- B. DNA polymerase
- C. HBeAg
- D. IgM Anti-HBc
Explanation: ***HBV DNA*** - **HBV DNA** is the **gold standard and most direct marker of active HBV replication** in modern clinical practice - **Quantitative HBV DNA (viral load)** precisely measures the level of viral replication and is essential for: - Diagnosing active infection - Monitoring disease progression - Guiding treatment decisions - Assessing treatment response - Detected by **PCR (Polymerase Chain Reaction)** or other nucleic acid amplification tests - Directly indicates the presence of replicating virus *HBeAg* - **HBeAg (Hepatitis B e-antigen)** is a marker of high viral replication in **HBeAg-positive chronic hepatitis B** - However, it has significant limitations: - **HBeAg-negative variants** can have active replication without HBeAg presence - Not present in all cases of active replication - Less direct than measuring actual viral DNA - Useful as a supplementary marker but not the primary indicator of replication *DNA polymerase* - **HBV DNA polymerase** is an enzyme essential for viral replication - While its activity correlates with replication, it is **not routinely measured** as a primary clinical marker - HBV DNA testing has replaced DNA polymerase assays in modern practice *IgM Anti-HBc* - **IgM Anti-HBc (IgM antibody to hepatitis B core antigen)** indicates **acute or recent HBV infection** - Reflects the **immune response** to infection, not viral replication itself - Can be present during acute phase even as viral replication is being controlled - Not a marker of ongoing chronic replication
Question 1375: Which additional gene is present in the Human T-cell Leukemia Virus (HTLV)?
- A. Gag
- B. Pol
- C. Env
- D. Tax (Correct Answer)
Explanation: ***Tax*** - The **Tax gene** is a unique regulatory gene found in **Human T-cell Leukemia Virus (HTLV)** that is crucial for its oncogenic potential. - It plays a vital role in **viral replication** and **cellular transformation** by modulating host gene expression. *Gag* - The **Gag gene** encodes for **structural proteins** (e.g., matrix, capsid, nucleocapsid) that form the **viral core** and are essential for assembly but are not unique to HTLV. - This gene is present in all retroviruses, including HIV, and is not an "additional" gene specific to HTLV. *Pol* - The **Pol gene** encodes for essential viral enzymes such as **reverse transcriptase**, **protease**, and **integrase**, which are necessary for viral replication and integration. - This gene is also conserved across all retroviruses and does not represent an additional gene specific to HTLV. *Env* - The **Env gene** codes for the **envelope glycoproteins** (e.g., surface and transmembrane proteins) that mediate viral entry into host cells and are involved in receptor binding. - This gene is also a common feature of retroviruses and is therefore not an "additional" gene unique to HTLV.
Question 1376: All are true regarding mumps, EXCEPT:
- A. Spreads through Stensen's duct to parotid gland (Correct Answer)
- B. Incubation period is 18-21 days
- C. Multiplies in respiratory epithelium
- D. Can cause aseptic meningitis
Explanation: ***Spreads through Stensen's duct to parotid gland*** - Mumps virus does NOT primarily enter the parotid gland via **Stensen's duct**; rather, it reaches the parotid glands via **hematogenous spread** after initial replication in the upper respiratory tract and regional lymph nodes. - Stensen's duct is the **excretory duct** for saliva drainage from the parotid gland, not a viral entry route. - This is the **false statement** in this EXCEPT question. *Incubation period is 18-21 days* - The typical incubation period for mumps is **16-18 days** (range 12-25 days), so 18-21 days falls within the acceptable range. - This relatively long incubation period allows for potential asymptomatic transmission before symptom onset. *Can cause aseptic meningitis* - Mumps is a well-known cause of **aseptic (viral) meningitis**, occurring in approximately **10-15%** of mumps cases. - CNS involvement can also include encephalitis, though this is less common. - Most cases of mumps meningitis resolve without permanent neurological sequelae. *Multiplies in respiratory epithelium* - Mumps virus is transmitted via **respiratory droplets** and initially replicates in the **nasopharyngeal mucosa and respiratory epithelial cells**. - This initial replication site leads to local viral shedding and subsequent viremia with systemic spread to glandular tissues (parotid, pancreas, testes, ovaries).
Question 1377: Reverse transcriptase is a RNA-dependent DNA polymerase. Which of the following uses it?
- A. Hepatitis A virus
- B. Hepatitis E virus
- C. Hepatitis C virus
- D. Hepatitis B virus (Correct Answer)
Explanation: ***Hepatitis B virus*** - Hepatitis B virus (HBV) is a **DNA virus** that replicates via an **RNA intermediate** using **reverse transcriptase**. - Its genome is a partially double-stranded circular DNA, and the enzyme is crucial for synthesizing the DNA genome from a pregenomic RNA template. *Hepatitis A virus* - Hepatitis A virus (HAV) is a **single-stranded RNA virus** (positive-sense) that replicates without a reverse transcriptase step. - Its replication involves direct translation of its RNA genome into viral proteins and replication via an RNA-dependent RNA polymerase. *Hepatitis E virus* - Hepatitis E virus (HEV) is a **single-stranded RNA virus** (positive-sense) that, like HAV, does not utilize reverse transcriptase for its replication. - It replicates in the cytoplasm of host cells using an **RNA-dependent RNA polymerase**. *Hepatitis C virus* - Hepatitis C virus (HCV) is a **single-stranded RNA virus** (positive-sense) belonging to the Flaviviridae family. - It replicates its RNA genome directly using an **RNA-dependent RNA polymerase** and does not involve a DNA intermediate or reverse transcription.
Question 1378: Which virus is most commonly recognized as a prototypical viral hemorrhagic fever in endemic regions of West Africa?
- A. Lassa fever virus (Correct Answer)
- B. West Nile virus
- C. Yellow fever virus
- D. Crimean-Congo hemorrhagic fever virus
Explanation: ***Lassa fever virus*** - Lassa fever is a prototypical **viral hemorrhagic fever (VHF)** endemic to West Africa, caused by an **Arenavirus** transmitted through contact with rodent (Mastomys) excreta. - Characterized by fever, hemorrhagic manifestations in severe cases (15-20%), and multi-organ involvement with high mortality in hospitalized patients. - Represents one of the most important VHFs due to its **endemic nature** affecting millions annually in West Africa. *Yellow fever virus* - Yellow fever causes hemorrhagic fever with prominent **jaundice** and **hepatic necrosis**, transmitted by *Aedes* mosquitoes. - A **Flavivirus** causing "yellow" fever due to liver damage, but vaccine-preventable and less commonly seen in modern practice in endemic regions. *West Nile virus* - A **Flavivirus** primarily causing **neuroinvasive disease** (meningitis, encephalitis) rather than hemorrhagic fever. - Hemorrhagic manifestations are **extremely rare** and not characteristic of West Nile virus infection. *Crimean-Congo hemorrhagic fever virus* - CCHF is a severe **tick-borne VHF** (Nairovirus) with prominent hemorrhagic features and high mortality (10-40%). - Endemic to **Africa, Asia, Eastern Europe, and Middle East** but NOT West Africa, distinguishing its geographic distribution from Lassa fever.
Question 1379: Active replication in hepatitis B infection is indicated by:
- A. HBeAg (Correct Answer)
- B. HBsAg
- C. HBcAg
- D. Anti-HBsAg
Explanation: ***HBeAg*** - **HBeAg (Hepatitis B e-antigen)** indicates **active viral replication** and **high infectivity** in hepatitis B infection. - Its presence signifies that the virus is actively multiplying, leading to a higher risk of transmission. *HBsAg* - **HBsAg (Hepatitis B surface antigen)** is the **first serological marker** to appear following acute infection and indicates **current infection** (either acute or chronic). - Its presence alone does not differentiate between active replication and a chronic carrier state with low viral activity. *HBcAg* - **HBcAg (Hepatitis B core antigen)** is an **intracellular antigen** found within infected hepatocytes and is typically **not detectable in serum**. - Its primary clinical utility is seen through **anti-HBc antibodies**, which indicate past or current infection. *Anti-HBsAg* - **Anti-HBsAg (Antibody to HBsAg)** indicates **immunity** to hepatitis B, either due to successful **vaccination** or **resolved infection**. - Its presence implies that the individual is no longer infected and has protective antibodies, rather than active replication.
Question 1380: Which of the following is NOT a poxvirus?
- A. Molluscum contagiosum
- B. Smallpox
- C. Cowpox
- D. Chickenpox (Correct Answer)
Explanation: ***Chicken pox*** - **Chickenpox** is caused by the **varicella-zoster virus (VZV)**, which is a member of the **Herpesviridae** family, not the Poxviridae family. - VZV is characterized by its ability to establish **latency** in sensory ganglia, leading to potential reactivation as **shingles** later in life. *Cow pox* - **Cowpox** is a **poxvirus** that causes skin lesions in cattle and can be transmitted to humans, historically being crucial for the development of the **smallpox vaccine**. - It belongs to the **Orthopoxvirus** genus within the Poxviridae family. *Molluscum contagiosum* - **Molluscum contagiosum** is caused by the **molluscum contagiosum virus (MCV)**, which is a specific type of **poxvirus** affecting humans. - It typically causes characteristic **pearly, umbilicated papules** on the skin and is transmitted by direct contact. *Small pox* - **Smallpox** was a severe infectious disease caused by the **variola virus**, a highly virulent member of the **Orthopoxvirus** genus classified within the Poxviridae family. - It was eradicated globally through vaccination efforts, making it one of the greatest achievements in public health.
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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