Virology — MCQs

Virology Indian Medical PG Practice Questions and MCQs

Question 1401: Causative organism of tropical spastic paraparesis is?

A. HIV 1
B. HIV 2
C. HBV
D. HTLV (Correct Answer)

Explanation: ***HTLV*** - **Human T-lymphotropic virus type 1 (HTLV-1)** is the definitive causative agent for **tropical spastic paraparesis (TSP)**, also known as **HTLV-1-associated myelopathy (HAM)**. - The virus primarily infects CD4+ T-cells and leads to chronic inflammation and demyelination within the spinal cord, particularly affecting the **thoracic spinothalamic tracts** and **corticospinal tracts**. *HIV 1* - **HIV-1** can cause vacuolar myelopathy, which is a different neurological complication that presents with similar symptoms to TSP but is a direct effect of HIV rather than HTLV-1 infection. - While both can cause myelopathies, **HIV-1** is not the causative agent for tropical spastic paraparesis itself; that is specifically linked to HTLV-1. *HIV 2* - **HIV-2** is less common than HIV-1 and primarily found in West Africa. It can also cause neurological complications, but it is not directly associated with **tropical spastic paraparesis**. - Its neurological manifestations are generally milder and less frequent compared to **HIV-1**, and not classically linked to TSP. *HBV* - **Hepatitis B virus (HBV)** is a hepadnavirus primarily affecting the liver, causing hepatitis, cirrhosis, and hepatocellular carcinoma. - **HBV** is not known to directly cause neurological conditions like tropical spastic paraparesis; its extrahepatic manifestations are typically vasculitis or neuromuscular syndromes, not myelopathy.

Question 1402: Which of the following viruses is NOT known to be associated with human cancers?

A. Hepatitis B virus
B. Parvovirus B-19 (Correct Answer)
C. Human Papillomavirus
D. Epstein-Barr virus

Explanation: ***Parvovirus B-19*** - Parvovirus B-19 is primarily associated with **fifth disease** in children and causes symptoms like rash and anemia, not cancer. - Unlike the other viruses listed, it has no established link to **human malignancies** [2]. *Papilloma virus* - Certain strains of **human papillomavirus (HPV)** are known to cause **cervical** and other cancers, making it a significant carcinogen [1][2]. - HPV is associated with the development of **kinetic lesions** that can progress to cancer. *Hepatitis B virus* - Hepatitis B virus is a well-established cause of **hepatocellular carcinoma** due to chronic liver inflammation and cirrhosis [2][3]. - It can lead to **viral oncogenesis** through integration into the host genome [3]. *Epstein Barr virus* - Epstein Barr virus (EBV) is linked to several cancers, including **Burkitt lymphoma** and **nasopharyngeal carcinoma** [2][4]. - It plays a role in immune evasion leading to **B-cell transformation**, which can result in malignancy [4]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, pp. 334-335. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 219-220. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, pp. 336-337. [4] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, pp. 335-336.

Question 1403: Which of the following statements about influenza is true?

A. Incubation period is 18-72 hours
B. Type-A virus can cause pandemics (Correct Answer)
C. Type-A virus is associated with Reye's syndrome when aspirin is used
D. Most infections are subclinical or mild

Explanation: ***Type-A virus can cause pandemics*** - **Influenza A virus** is responsible for severe epidemics and **pandemics** due to its ability to undergo significant **antigenic shifts** (e.g., H1N1, H3N2), leading to new strains to which the human population has little or no immunity. - **Only Influenza A causes pandemics**; Influenza B and C cause only localized outbreaks and epidemics. - Its high genetic variability and ability to infect multiple species (avian, swine, human) contribute to its pandemic potential. *Incubation period is 18-72 hours* - The typical **incubation period for influenza** is **1 to 4 days**, with an average of about **2 days** (48 hours). - While 18-72 hours (0.75-3 days) overlaps with this range, it is **too narrow** and does not represent the complete, commonly cited range of 1-4 days. - This statement is incomplete and therefore not the best answer. *Type-A virus is associated with Reye's syndrome when aspirin is used* - **Reye's syndrome** is a rare but severe condition that can follow viral infections, including **both Influenza A and B**, particularly when **aspirin (salicylates)** is administered to children or adolescents. - While this statement is not false (Type-A IS associated), it is **misleading** because it implies Type-A has a specific or unique association, when in fact **both Influenza A and B** are equally associated with Reye's syndrome in the context of aspirin use. - The association is with influenza viruses in general, not specifically Type-A. *Most infections are subclinical or mild* - This is **incorrect**. Most influenza infections are **symptomatic**, presenting with fever, cough, sore throat, myalgia, and malaise. - Influenza is well-known for causing significant **morbidity and mortality**, especially in vulnerable populations (elderly, immunocompromised, young children). - While some infections may be mild, particularly in vaccinated individuals, the majority cause clinically apparent disease.

Question 1404: What is the primary disease associated with Enterovirus 71?

A. Hepatitis E
B. Hepatitis G
C. Hand, foot, and mouth disease (Correct Answer)
D. Hepatitis C

Explanation: ***Hand, foot, and mouth disease*** - **Enterovirus 71** is a major causative agent of **hand, foot, and mouth disease (HFMD)**, especially in severe cases involving neurological complications. - HFMD is characterized by **fever**, **oral lesions**, and a **rash** on the hands and feet, particularly common in young children. *Hepatitis E* - **Hepatitis E** is caused by the **Hepatitis E virus (HEV)**, a distinct RNA virus, not an enterovirus. - It primarily causes **acute viral hepatitis**, particularly transmitted via the fecal-oral route. *Hepatitis G* - **Hepatitis G virus (HGV)**, also known as **GBV-C**, is a flavivirus, which is distinct from enteroviruses. - Its clinical significance and role in causing hepatitis are still debated, and it's not a primary cause of symptomatic liver disease. *Hepatitis C* - **Hepatitis C** is caused by the **Hepatitis C virus (HCV)**, an RNA virus belonging to the *Flaviviridae* family, genetically distinct from enteroviruses. - HCV is a major cause of **chronic hepatitis**, cirrhosis, and hepatocellular carcinoma.

Question 1405: Fifth disease is caused by which virus?

A. Parvovirus B19 (Correct Answer)
B. Human Papillomavirus (HPV)
C. Hepatitis Virus
D. Cytomegalovirus (CMV)

Explanation: ***Parvovirus B19*** - **Parvovirus B19** is the sole member of the *Erythrovirus* genus known to cause disease in humans, primarily responsible for **Fifth disease**, also known as **erythema infectiosum**. - This virus targets and replicates in **erythroid progenitor cells**, leading to a characteristic rash and, in some cases, transient aplastic crisis. *Human Papillomavirus (HPV)* - HPV is known to cause **warts** and is a major risk factor for various cancers, including **cervical cancer**, not Fifth disease. - It infects epithelial cells and leads to proliferative lesions, with over 100 different types identified. *Hepatitis Virus* - Hepatitis viruses (e.g., A, B, C, D, E) primarily cause **inflammation of the liver** and are associated with acute or chronic liver disease. - They are not associated with the characteristic rash or symptoms of Fifth disease. *Cytomegalovirus (CMV)* - CMV is a common virus that usually causes **asymptomatic infection** but can lead to severe disease in immunocompromised individuals or newborns. - It is known for causing **congenital infections** and opportunistic infections in transplant recipients, not Fifth disease.

Question 1406: Which test is primarily used for the quantification of viral infectivity?

A. Plaque assay (Correct Answer)
B. Haemagglutination
C. Cytopathic effect
D. Electron microscopy

Explanation: ***Plaque assay*** - The **plaque assay** directly measures the number of **infectious viral particles** in a sample, expressed as plaque-forming units (PFU) per milliliter. - It involves inoculating host cells with serially diluted virus, leading to localized areas of cell lysis or destruction called **plaques**, which are then counted. *Cytopathic effect* - **Cytopathic effect (CPE)** refers to the visual changes induced in host cells by viral infection, such as cell rounding, lysis, or syncytia formation. - While it indicates an infection is occurring, it does not reliably **quantify** the number of infectious viral particles. *Haemagglutination* - **Hemagglutination assay** measures the ability of certain viruses to agglutinate red blood cells due to binding of viral proteins to receptors on the cell surface. - This method quantifies the **total number of viral particles** (infectious or non-infectious) that possess hemagglutinating activity, not specifically their infectivity. *Electron microscopy* - **Electron microscopy** allows for direct visualization of virus particles and their morphological characteristics. - It can determine the **total number of physical viral particles** in a sample but cannot distinguish between infectious and non-infectious particles.

Question 1407: Which of the following statements about Zika virus is false?

A. Transmitted by Aedes mosquito
B. Zika is Flavi virus
C. Zika virus cannot be transmitted through breast milk
D. Zika virus does not cause microcephaly (Correct Answer)

Explanation: ***Zika virus does not cause microcephaly*** - This statement is false because **Zika virus** is well-known for causing **microcephaly** and other severe birth defects in infants whose mothers were infected during pregnancy. - The association between maternal Zika infection and fetal microcephaly has been extensively documented and is one of the most critical public health concerns related to the virus. *Transmitted by Aedes mosquito* - This statement is true; **Aedes aegypti** and **Aedes albopictus** mosquitoes are the primary vectors responsible for transmitting the Zika virus to humans. - These mosquitoes are also known to transmit other arboviruses like **dengue** and **chikungunya**. *Zika is Flavi virus* - This statement is true; Zika virus belongs to the **Flaviridae family** and the *Flavivirus genus*, which also includes dengue, yellow fever, and West Nile viruses. - Members of this family are typically **single-stranded RNA viruses** with an enveloped capsid. *Zika virus cannot be transmitted through breast milk* - This statement is true; while Zika virus RNA has been detected in breast milk, there is currently **no confirmed evidence** of transmission to infants through breastfeeding. - Current guidelines from health organizations generally recommend that mothers in Zika-affected areas continue to breastfeed due to the benefits of breastfeeding outweighing the theoretical risk.

Question 1408: Which of the following serves as the cellular receptor for Epstein-Barr Virus (EBV)?

A. CD 21 (Correct Answer)
B. CD 22
C. CD 20
D. CD 23

Explanation: ***CD 21*** - **CD21**, also known as the **complement receptor 2 (CR2)**, is the primary cellular receptor for Epstein-Barr Virus (EBV). - EBV predominantly infects **B lymphocytes** by binding to CD21, allowing viral entry. *CD 20* - **CD20** is a transmembrane protein found on **B-lymphocytes**, but it is **not** the receptor for EBV. - It is often targeted in cancer therapy for B-cell lymphomas (e.g., with **Rituximab**). *CD 22* - **CD22** is an inhibitory co-receptor on B-lymphocytes that **regulates B-cell activation**. - While present on B-cells, it does **not** serve as the entry receptor for EBV. *CD 23* - **CD23** is the **low-affinity IgE receptor (FcεRII)**, found on activated B cells, macrophages, and other immune cells. - It is **not** the receptor used by EBV for cellular entry; rather, it is involved in **IgE-mediated immune responses**.

Question 1409: Dengue fever is caused by:

A. Orthomyxo virus
B. Flavivirus (Correct Answer)
C. Paramyxo virus
D. Bunya virus

Explanation: ***Flavivirus*** - Dengue fever is caused by the **dengue virus**, which belongs to the **Flaviviridae family** (genus Flavivirus). - There are **four serotypes** of dengue virus (DENV-1, DENV-2, DENV-3, DENV-4), all of which can cause dengue fever. - Flaviviruses are **RNA viruses** transmitted by **arthropod vectors** (primarily *Aedes aegypti* and *Aedes albopictus* mosquitoes). - Other important flaviviruses include **Yellow fever virus**, **Zika virus**, **West Nile virus**, and **Japanese encephalitis virus**. *Orthomyxo virus* - This family includes the **influenza viruses** (influenza A, B, C, D) which cause seasonal flu and pandemic influenza. - They are **segmented RNA viruses** transmitted via **respiratory droplets**, not arthropod vectors. - Characterized by surface proteins **hemagglutinin (H)** and **neuraminidase (N)**. *Paramyxo virus* - This family includes viruses causing **measles**, **mumps**, **parainfluenza**, and **respiratory syncytial virus (RSV)**. - These are **non-segmented negative-sense RNA viruses** transmitted through **respiratory secretions** and close contact. - Not transmitted by arthropod vectors. *Bunya virus* - The **Bunyaviridae family** (now reclassified into multiple families) includes various arboviruses like **Crimean-Congo hemorrhagic fever virus** and **Rift Valley fever virus**. - Also includes **hantaviruses** transmitted by rodents (not arthropods). - While some bunyaviruses cause hemorrhagic fevers, dengue virus specifically belongs to the **Flaviviridae family**, not Bunyaviridae.

Question 1410: Virus lacking hemagglutinin and neuraminidase but having a prominent membrane fusion (F) protein as its major surface glycoprotein is?

A. Herpes Simplex Virus (HSV)
B. Cytomegalovirus (CMV)
C. Respiratory Syncytial Virus (RSV) (Correct Answer)
D. Epstein-Barr Virus (EBV)

Explanation: ***Respiratory Syncytial Virus (RSV)*** - RSV is characterized by the presence of a **prominent fusion (F) protein** as its major surface glycoprotein, which mediates membrane fusion and viral entry into host cells. - Unlike influenza viruses, RSV **lacks hemagglutinin and neuraminidase proteins**. - The **F protein is the primary virulence factor** and target for antibody-mediated immunity. *Cytomegalovirus (CMV)* - CMV is a **herpesvirus** that does not possess hemagglutinin or neuraminidase. - Its entry mechanism involves **multiple glycoproteins** (gB, gH, gL) that work together for fusion, rather than a single prominent F protein like RSV. *Herpes Simplex Virus (HSV)* - HSV is another **herpesvirus** that utilizes **various glycoproteins** (gB, gD, gH, gL) working in concert for binding and membrane fusion. - It **lacks hemagglutinin and neuraminidase** but does not have a single prominent fusion protein. *Epstein-Barr Virus (EBV)* - EBV, a member of the **herpesvirus family**, also does not have hemagglutinin or neuraminidase. - Its entry involves **specific glycoproteins** (gH, gL, gp42, gB) that are responsible for receptor binding and membrane fusion in a coordinated manner.

Practice by Chapter

Virus Structure and Classification

Practice Questions

Viral Replication

Practice Questions

Pathogenesis of Viral Infections

Practice Questions

DNA Viruses: Herpesviruses

Practice Questions

DNA Viruses: Poxviruses and Adenoviruses

Practice Questions

Hepatitis Viruses

Practice Questions

RNA Viruses: Orthomyxoviruses

Practice Questions

RNA Viruses: Paramyxoviruses

Practice Questions

Enteroviruses and Rhinoviruses

Practice Questions

Arboviruses

Practice Questions

HIV and Retroviruses

Practice Questions

Oncogenic Viruses

Practice Questions

Want unlimited practice?

Get full access to all questions, explanations, and performance tracking.

Start For Free

Virology — MCQs

Virology — MCQs

On this page

Practice by Chapter

Want unlimited practice?