Virology — MCQs

Virology Indian Medical PG Practice Questions and MCQs

Question 1411: Which of the following viruses is considered a defective virus that requires another virus for its replication?

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

Explanation: ***Hepatitis D virus (HDV)*** - **Hepatitis D virus (HDV)** is a unique RNA virus that is **defective** and requires the presence of **Hepatitis B virus (HBV)** and its surface antigen **(HBsAg)** for replication and assembly. - HDV infection can occur as **co-infection** (simultaneous HBV and HDV) or **superinfection** (HDV infection in an existing HBV carrier), often leading to **more severe liver disease**. - HDV is a **satellite virus** that cannot complete its life cycle independently. *Incorrect: Hepatitis A virus (HAV)* - **Hepatitis A virus (HAV)** is a **picornavirus** that causes acute hepatitis and **replicates independently** without the need for another helper virus. - It is transmitted via the **fecal-oral route** and does **not cause chronic infection**. *Incorrect: Hepatitis B virus (HBV)* - **Hepatitis B virus (HBV)** is a **hepadnavirus** that **replicates independently** and produces its own viral envelopes. - HBV is the **helper virus required for HDV replication**, but HBV itself does not require another virus to complete its life cycle. *Incorrect: Hepatitis C virus (HCV)* - **Hepatitis C virus (HCV)** is a **flavivirus** that can **replicate autonomously** and cause both acute and chronic hepatitis. - It does **not require a helper virus** for its replication, unlike HDV.

Question 1412: Dengue hemorrhagic fever is primarily associated with which type of infection?

A. Infection with the same dengue virus repeatedly
B. Infection with dengue virus in an immunocompromised host
C. Infection with multiple serotypes of the dengue virus
D. Secondary infection with a different serotype of the dengue virus (Correct Answer)

Explanation: ***Secondary infection with a different serotype of the dengue virus*** - **Dengue hemorrhagic fever (DHF)** is primarily associated with **antibody-dependent enhancement (ADE)**. This occurs when a person who has previously been infected with one dengue serotype is subsequently infected with a different serotype. - The pre-existing, non-neutralizing antibodies from the first infection bind to the new serotype, forming immune complexes that enhance viral uptake into monocytes and macrophages, leading to higher viral loads and a more severe disease presentation. *Infection with the same dengue virus repeatedly* - Infection with the **same serotype** of dengue virus generally leads to **long-lasting homotypic immunity**, meaning subsequent infections with that exact same serotype are unlikely and do not typically cause DHF. - Repeated infections with the same serotype do not trigger the same **ADE mechanism** seen with different serotypes. *Infection with dengue virus in an immunocompromised host* - While immunocompromised individuals may experience more severe disease with many infections, **immunocompromised status** is not the primary or specific mechanism driving the development of **dengue hemorrhagic fever (DHF)**. - The key factor for DHF is the **immunological response** to a secondary infection with a different serotype, rather than a general state of immunosuppression. *Infection with multiple serotypes of the dengue virus* - While exposure to multiple serotypes is necessary, the critical factor for DHF is the **timing and sequence** of these infections, specifically a **secondary infection** with a *different* serotype. - Simply being infected with multiple serotypes concurrently or without a prior infection of a different serotype doesn't fully explain the **ADE mechanism** leading to DHF.

Question 1413: Herpes zoster ophthalmicus is caused by:

A. VZV (Correct Answer)
B. HPV
C. HSV
D. CMV

Explanation: ***Correct Answer: VZV*** - **Varicella-zoster virus (VZV)** is the causative agent of **herpes zoster ophthalmicus**, which is a reactivation of the virus in the ophthalmic division of the trigeminal nerve. - The initial infection with VZV causes **chickenpox (varicella)**, and the virus remains dormant in sensory ganglia to reactivate later as shingles. *Incorrect - HPV* - **Human papillomavirus (HPV)** is primarily known for causing **warts** and is a significant risk factor for certain **cancers**, particularly cervical cancer. - HPV does not cause vesicular rashes associated with herpes zoster or ophthalmic involvement. *Incorrect - HSV* - **Herpes simplex virus (HSV)** causes different forms of herpes infections, such as **oral (cold sores)** and **genital herpes**, and can also cause keratitis but is distinct from zoster ophthalmicus. - While HSV can affect the eye, leading to **herpes simplex keratitis**, it produces a different clinical picture and does not involve the dermatomal rash characteristic of zoster. *Incorrect - CMV* - **Cytomegalovirus (CMV)** is a common virus often causing asymptomatic infections in healthy individuals. - In immunocompromised patients, CMV can cause serious diseases, including **retinitis**, but it does not cause herpes zoster ophthalmicus.

Question 1414: Which virus is implicated in Burkitt's lymphoma?

A. Epstein-Barr virus (Correct Answer)
B. Arbovirus
C. Picornavirus
D. Coxsackievirus

Explanation: ***Epstein-Barr virus*** - The **Epstein-Barr virus (EBV)** is strongly associated with Burkitt's lymphoma, particularly the endemic form found in equatorial Africa. - EBV infection leads to **B-cell proliferation** and can promote oncogenesis in the presence of other co-factors, such as a c-MYC translocation. *Arbovirus* - **Arboviruses** are transmitted by arthropod vectors (e.g., mosquitoes, ticks) and cause diseases like dengue fever and Zika virus, not Burkitt's lymphoma. - They primarily cause **viremia** and symptoms related to central nervous system involvement or hemorrhagic fever. *Picornavirus* - **Picornaviruses** are a family of small, non-enveloped RNA viruses that include enteroviruses (e.g., poliovirus, coxsackievirus) and rhinoviruses. - They typically cause diseases like **poliomyelitis**, **common cold**, and **gastroenteritis**, not lymphoid malignancies. *Coxsackievirus* - **Coxsackieviruses** are a genus of enteroviruses within the Picornaviridae family and are known to cause diseases such as hand-foot-and-mouth disease, myocarditis, and aseptic meningitis. - There is **no established link** between Coxsackievirus infection and Burkitt's lymphoma.

Question 1415: Which pox virus does Variola belong to?

A. Parapoxvirus
B. Orthopoxvirus (Correct Answer)
C. Yatapox virus
D. Molluscipox virus

Explanation: ***Orthopoxvirus*** - **Variola virus**, the causative agent of **smallpox**, is a member of the **Orthopoxvirus genus**. - Other notable members of this genus include **vaccinia virus** (used in smallpox vaccine) and **monkeypox virus**. *Parapoxvirus* - This genus includes viruses such as **Orf virus**, which causes contagious pustular dermatitis in sheep and goats, occasionally transmitted to humans. - Parapoxviruses typically cause localized skin lesions and are not associated with **smallpox**. *Yatapox virus* - The **Yatapox virus genus** includes the **Tanapox virus** and **Yabapox virus**, which primarily affect monkeys but can cause mild, self-limiting skin lesions in humans. - They are distinct from the **Variola virus** and do not cause smallpox. *Molluscipox virus* - This genus contains **Molluscum contagiosum virus**, which causes **molluscum contagiosum**, a common skin infection characterized by small, flesh-colored, dome-shaped papules. - It is genetically and clinically distinct from **Variola virus**.

Question 1416: All of the following are true about the papovavirus except:

A. Papovaviruses can produce papillomas in humans.
B. They are RNA viruses. (Correct Answer)
C. SV - 40 is oncogenic
D. They are non-enveloped icosahedral viruses

Explanation: ***They are RNA viruses*** - Papovaviruses, including **polyomaviruses** and **papillomaviruses**, are **double-stranded DNA viruses**, not RNA viruses. - Their genome is composed of **DNA**, which is a key characteristic distinguishing them from RNA viruses. *Papovaviruses can produce papillomas in humans* - **Human Papillomaviruses (HPVs)**, a subgroup of papovaviruses, are well-known for causing **papillomas** (warts) in humans. - Certain high-risk HPVs are also associated with **cervical cancer** and other anogenital cancers. *SV - 40 is oncogenic* - **Simian Virus 40 (SV40)**, a type of polyomavirus (which falls under the broader papovavirus group), is indeed **oncogenic** in certain animal models. - It has been studied extensively for its ability to induce tumors and transform cells in vitro through its **tumor antigens**. *They are non-enveloped icosahedral viruses* - Both **polyomaviruses** and **papillomaviruses** share the structural characteristic of being **non-enveloped**. - They also possess an **icosahedral capsid** symmetry, which encases their DNA genome.

Question 1417: The EBV receptor located on the surface of B cells is?

A. CD23
B. CD24
C. CD22
D. CD21 (Correct Answer)

Explanation: ***CD21*** - CD21 acts as a receptor for **Epstein-Barr Virus (EBV)** on the surface of B cells, facilitating viral entry [1][2]. - It also plays a role in B cell activation and **signal transduction** upon antigen binding [1]. *CD22* - CD22 is a **negative regulatory** molecule that contributes to B cell function but does not serve as a receptor for EBV. - It primarily modulates the response to **B cell receptor (BCR)** signaling. *CD24* - CD24 is a **glycoprotein** involved in cell adhesion and does not act as a receptor for EBV on B cells. - It is not prominently associated with the functions related to viral entry or B cell activation. *CD23* - CD23 is a low-affinity IgE receptor involved in regulating **B cell activation**, but it is not the receptor for EBV. - Its main roles relate to **allergic responses** and not viral interactions. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 199-200. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Infectious Diseases, pp. 368-369.

Question 1418: Which of the following is an RNA oncogenic virus?

A. Cytomegalovirus (CMV)
B. Hepatitis B Virus (HBV)
C. Human T-lymphotropic Virus (HTLV) (Correct Answer)
D. Human Immunodeficiency Virus (HIV)

Explanation: ***Human T-lymphotropic Virus (HTLV)*** - **HTLV-1** is a well-established **RNA oncogenic virus** that causes Adult T-cell Leukemia/Lymphoma (ATLL). - It utilizes **reverse transcriptase** to convert its RNA genome into DNA, which then integrates into the host cell's genome, leading to malignant transformation. *Cytomegalovirus (CMV)* - CMV is a **DNA virus** and belongs to the Herpesviridae family. - While it can cause disease, it is not primarily classified as an **oncogenic virus**, although some studies suggest associations with certain cancers. *Hepatitis B Virus (HBV)* - HBV is a **DNA virus** that primarily causes acute and chronic hepatitis. - It is a major risk factor for **hepatocellular carcinoma (HCC)**, but it itself is a DNA virus, not an RNA virus. *Human Immunodeficiency Virus (HIV)* - HIV is an **RNA retrovirus**, but it is generally considered **non-oncogenic** in the direct sense. - While HIV-infected individuals have an increased risk of certain cancers (e.g., Kaposi's sarcoma, non-Hodgkin lymphoma), these are usually due to **immunosuppression** allowing co-infecting oncogenic viruses (like HHV-8 or EBV) to proliferate, rather than direct oncogenic action of HIV itself.

Question 1419: Which virus characteristically reactivates in a dermatomal distribution?

A. Herpes simplex
B. Herpes zoster (Correct Answer)
C. Rotavirus
D. Influenza virus

Explanation: ***Herpes zoster (Correct Answer)*** - This virus, also known as **varicella-zoster virus (VZV)**, causes **chickenpox** during primary infection and remains latent in **sensory ganglia** (dorsal root ganglia). - Upon reactivation, it travels along the **sensory nerve** to the skin, producing a characteristic **vesicular rash in a dermatomal distribution**. - This dermatomal pattern is the hallmark clinical feature that distinguishes zoster reactivation. *Herpes simplex (Incorrect)* - **Herpes simplex virus (HSV)** typically causes **localized outbreaks** like cold sores (HSV-1) or genital herpes (HSV-2). - While it establishes latency in sensory ganglia, its reactivation pattern usually involves a **smaller, localized area** rather than a full dermatome. - Reactivation occurs at the same site repeatedly, not in a dermatomal distribution. *Influenza virus (Incorrect)* - This is a **respiratory virus** that causes acute systemic symptoms like fever, cough, and myalgia. - It does **not establish latency** in ganglia or any other tissue. - It causes no skin manifestations or dermatomal rashes; it primarily affects the **respiratory tract**. *Rotavirus (Incorrect)* - Rotavirus is a common cause of **gastroenteritis**, particularly in infants and young children. - It replicates in the **gastrointestinal tract** and causes severe diarrhea and vomiting. - It does **not establish latency** and has no skin manifestations or dermatomal distribution.

Question 1420: Which of the following statements about Norwalk virus is false?

A. Is a RNA virus
B. Causes gastroenteritis
C. Cultivated in cell culture (Correct Answer)
D. Belongs to Caliciviridae

Explanation: ***Cultivated in cell culture*** - **Norwalk virus** (now known as **norovirus**) is notoriously difficult to cultivate in standard laboratory cell cultures, making research and vaccine development challenging. - Its inability to grow in vitro is a defining characteristic, differentiating it from many other common viruses. *Belongs to calciviridae* - This statement is **true**; Norwalk virus is the prototype and best-known member of the genus *Norovirus* within the family **Caliciviridae**. - **Caliciviridae** are a family of non-enveloped, positive-sense, single-stranded RNA viruses. *Causes gastroenteritis* - This statement is **true**; Norovirus is the leading cause of **acute gastroenteritis** worldwide, particularly in outbreaks in crowded settings such as cruise ships, hospitals, and schools. - It causes symptoms like **nausea, vomiting, diarrhea**, and abdominal cramps. *Is a RNA virus* - This statement is **true**; Norovirus has a **single-stranded, positive-sense RNA genome**. - Its RNA genome is essential for its replication cycle as it can directly serve as mRNA.

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?