Virology — MCQs
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Most common pox virus infection in humans is?
Which paramyxovirus does not have hemagglutinin and neuraminidase but has a membrane fusion protein?
Rubella virus belongs to which family?
Genital warts are caused by which virus?
Coxsackievirus A16 is associated with which of the following conditions?
Acute Hemorrhagic Conjunctivitis is primarily caused by which type of Enterovirus?
What is the Australian antigen for hepatitis B?
HTLV-1 can be transmitted by -
What is a potential outcome of the integration of a viral genome into a host cell chromosome?
Von Magnus phenomenon:
Virology Indian Medical PG Practice Questions and MCQs
Question 1331: Most common pox virus infection in humans is?
- A. Smallpox
- B. Monkeypox
- C. Cowpox
- D. Molluscum contagiosum (Correct Answer)
Explanation: ***Molluscum contagiosum*** - This is a common, **benign viral skin infection** that causes small, pearl-like papules with central umbilication. - It is highly prevalent, especially in children, sexually active adults, and immunocompromised individuals, making it the most frequent human poxvirus infection. *Smallpox* - While historically significant, **smallpox** was eradicated globally in 1980 through widespread vaccination efforts. - It is no longer a naturally occurring infection in humans. *Monkeypox* - **Monkeypox** is a zoonotic disease that has recently seen outbreaks, but it is not as widespread or common as molluscum contagiosum. - It is characterized by fever, lymphadenopathy, and a distinctive rash, often with a more severe clinical presentation than molluscum. *Cowpox* - **Cowpox** is a rare disease primarily found in animals (e.g., cats, rodents) and occasionally transmitted to humans, typically through contact with infected animals. - Human infections are sporadic and far less common than molluscum contagiosum.
Question 1332: Which paramyxovirus does not have hemagglutinin and neuraminidase but has a membrane fusion protein?
- A. Measles
- B. Parainfluenza
- C. RSV (Correct Answer)
- D. Mumps
Explanation: ***RSV*** - **Respiratory Syncytial Virus (RSV)** is unique among paramyxoviruses because it lacks both **hemagglutinin (H)** and **neuraminidase (N)** glycoproteins. - Its pathogenicity relies on its **fusion (F) protein**, which causes respiratory epithelial cells to fuse, forming **syncytia**. *Measles* - The **measles virus** (Morbillivirus) possesses both **hemagglutinin (H)** and **fusion (F)** proteins, but it lacks neuraminidase. - The **H protein** is responsible for viral attachment, while the **F protein** mediates membrane fusion and syncytia formation. *Parainfluenza* - **Parainfluenza viruses** all possess both **hemagglutinin-neuraminidase (HN)** protein and **fusion (F)** protein. - The **HN protein** is responsible for both receptor binding and cleaving sialic acid residues, aiding in viral release. *Mumps* - The **mumps virus** also belongs to the paramyxovirus family and possesses both a **hemagglutinin-neuraminidase (HN)** protein and a **fusion (F)** protein. - These proteins are crucial for its ability to attach to host cells and mediate viral entry.
Question 1333: Rubella virus belongs to which family?
- A. Orthomyxovirus
- B. Rheovirus
- C. Togavirus (Correct Answer)
- D. Picornavirus
Explanation: ***Togavirus*** - The **Rubella virus** is categorized under the family **Togaviridae**, specifically within the genus *Rubivirus*. - This classification is based on its genetic structure, being an **enveloped, positive-sense, single-stranded RNA virus**. *Rheovirus* - **Reoviruses** are characterized by a **double-stranded segmented RNA genome** and are typically non-enveloped. - This contrasts with Rubella's single-stranded, non-segmented RNA and enveloped structure. *Picornavirus* - **Picornaviruses** are a family of **non-enveloped, positive-sense, single-stranded RNA viruses** that are structurally different from Rubella. - Examples include species like **poliovirus** and **rhinovirus**, which do not share the distinct biological properties of Rubella. *Orthomyxovirus* - **Orthomyxoviruses** are a family of **enveloped, negative-sense, segmented RNA viruses**, which includes influenza viruses. - Their genomic organization and replication strategy are fundamentally different from those of the Rubella virus.
Question 1334: Genital warts are caused by which virus?
- A. Cytomegalovirus (CMV)
- B. Herpes simplex virus (HSV)
- C. Human Papillomavirus (HPV) (Correct Answer)
- D. Varicella zoster virus (VZV)
Explanation: ***Human Papillomavirus (HPV)*** - **HPV** is the causative agent of **genital warts**, which are benign epithelial growths. - Specific low-risk HPV types, primarily **HPV types 6 and 11**, are responsible for the vast majority of genital wart cases. *Herpes simplex virus (HSV)* - **HSV** causes **genital herpes**, characterized by painful blisters and ulcers, not warts. - There are two main types: **HSV-1** (often oral herpes) and **HSV-2** (primarily genital herpes). *Cytomegalovirus (CMV)* - **CMV** is a common virus that usually causes **asymptomatic infection** in healthy individuals but can lead to severe disease in immunocompromised patients or neonates. - It is not associated with the formation of genital warts. *Varicella zoster virus (VZV)* - **VZV** is responsible for **chickenpox** (varicella) in primary infection and **shingles** (herpes zoster) during reactivation. - It does not cause genital warts.
Question 1335: Coxsackievirus A16 is associated with which of the following conditions?
- A. Herpangina
- B. Hand-foot-mouth disease (Correct Answer)
- C. Yellow fever
- D. Myocarditis
Explanation: ***Hand-foot-mouth disease*** - **Coxsackievirus A16** is one of the most common causative agents of **hand-foot-mouth disease**, characterized by fever, oral ulcers, and a rash on the hands and feet. - This viral infection is highly contagious and frequently seen in young children. *Herpangina* - While also caused by **Coxsackieviruses** (primarily **Coxsackievirus A** types like A10 or A2), **herpangina** typically presents with lesions restricted to the posterior oropharynx, without the characteristic hand and foot rash seen in HFMD. - It involves sudden onset of fever, sore throat, and small vesicles or ulcers on the **soft palate, tonsillar pillars, and uvula**. *Yellow fever* - **Yellow fever** is caused by the **yellow fever virus**, a flavivirus, and is transmitted by mosquitoes. - It presents with fever, jaundice, and hemorrhagic symptoms, completely distinct from enteroviral infections. *Myocarditis* - **Myocarditis** can be caused by various viruses, including other **enteroviruses** like **Coxsackievirus B** types (e.g., B1-B5), along with adenoviruses and parvovirus B19. - However, **Coxsackievirus A16** is not a primary cause of myocarditis; its association is predominantly with hand-foot-mouth disease.
Question 1336: Acute Hemorrhagic Conjunctivitis is primarily caused by which type of Enterovirus?
- A. Enterovirus type 68
- B. Enterovirus type 69
- C. Enterovirus type 70 (Correct Answer)
- D. Enterovirus type 71
Explanation: ***Enterovirus type 70*** - **Enterovirus type 70** is the most common cause of **Acute Hemorrhagic Conjunctivitis (AHC)**, particularly in epidemic outbreaks. - AHC presents with rapid onset of **ocular pain**, **redness**, **swelling**, and **subconjunctival hemorrhages**. *Enterovirus type 68* - **Enterovirus D68 (EV-D68)** is primarily known for causing **respiratory illnesses**, ranging from mild to severe, and is associated with acute flaccid myelitis. - While it can cause respiratory symptoms, it is not a primary cause of **Acute Hemorrhagic Conjunctivitis**. *Enterovirus type 69* - **Enterovirus type 69** is a rare serotype and is not typically associated with specific human diseases or large-scale outbreaks. - Unlike EV70, it is not recognized as a significant cause of **conjunctivitis**. *Enterovirus type 71* - **Enterovirus A71 (EV-A71)** is a common cause of **hand, foot, and mouth disease (HFMD)**, especially in children, and can also lead to severe neurological complications. - While it causes various infections, it is not the primary cause of **hemorrhagic conjunctivitis**.
Question 1337: What is the Australian antigen for hepatitis B?
- A. HBsAg (Correct Answer)
- B. HBeAg
- C. HBDAg
- D. HBV DNA
Explanation: ***HBsAg*** - **HBsAg** stands for **Hepatitis B surface antigen**, which was originally discovered by Baruch Blumberg in 1965 and was initially called the **Australia antigen** due to its discovery in the serum of an Australian aboriginal. - Its presence indicates an **active hepatitis B infection**, either acute or chronic. *HBeAg* - **HBeAg** (Hepatitis B e-antigen) is a marker of **viral replication** and **infectivity**. - It is distinct from HBsAg and indicates a high level of **transmissibility** of the virus. *HBDAg* - **HBDAg** is not a standard or recognized antigen for hepatitis B. - The correct antigen for hepatitis D is **HDAg** (Hepatitis D antigen), which is only found in individuals co-infected with hepatitis D virus and hepatitis B virus. *HBV DNA* - **HBV DNA** refers to the viral genetic material of the hepatitis B virus. - While its presence indicates active viral replication and is used to monitor **viral load**, it is not an antigen but rather the **viral genome** itself.
Question 1338: HTLV-1 can be transmitted by -
- A. Blood transfusion (Correct Answer)
- B. Droplet inhalation
- C. Contaminated water
- D. Animal bite
Explanation: ***Blood transfusion*** - **HTLV-1 (Human T-lymphotropic virus type 1)** can be effectively transmitted through **blood products** and is a significant concern for blood safety. - **Major transmission routes of HTLV-1 include**: blood transfusion, breastfeeding (mother-to-child, most common in endemic areas), sexual contact, and sharing contaminated needles. - Screening of blood donors for HTLV-1/2 antibodies is crucial in endemic areas (Japan, Caribbean, parts of Africa and South America) to prevent transfusion-associated transmission. - This mode of transmission has been significantly reduced in countries with mandatory donor screening programs. *Droplet inhalation* - **HTLV-1** is **not transmitted via respiratory droplets** or aerosols, unlike viruses such as influenza or SARS-CoV-2. - Transmission requires direct contact with **infected cells** (primarily CD4+ T lymphocytes) or bodily fluids containing infected cells. - HTLV-1 is a cell-associated virus, not present free in respiratory secretions. *Contaminated water* - **HTLV-1** is a **blood-borne and sexually transmitted retrovirus** and is not transmitted through contaminated water. - The virus cannot survive in water and requires cell-to-cell contact or cell-containing fluids for transmission. - Waterborne diseases are caused by pathogens that can survive in aquatic environments, which does not apply to HTLV-1. *Animal bite* - **HTLV-1** is a **human-specific retrovirus** with no animal reservoir; it is not transmitted through animal bites. - Unlike zoonotic viruses (rabies, certain arboviruses), HTLV-1 transmission is strictly human-to-human. - The virus specifically infects human CD4+ T cells and does not have vectors or animal hosts.
Question 1339: What is a potential outcome of the integration of a viral genome into a host cell chromosome?
- A. Altered growth
- B. Malignancy
- C. Latency
- D. All of the options (Correct Answer)
Explanation: ***All of the options*** - The insertion of a viral genome, known as a **provirus**, into the host chromosome can lead to a variety of sustained and complex interactions. - This integration can cause **long-term changes** in cell behavior, including altered gene expression and cell cycle regulation, which may manifest as any of the specified outcomes. *Malignancy* - Viral integration can interrupt or activate host genes, such as **oncogenes** or **tumor suppressor genes**, leading to uncontrolled cell proliferation and potential tumor formation. - An example is **human papillomavirus (HPV)** integrating into host cells, increasing the risk of cervical cancer. *Altered growth* - Integration can change the cell's normal growth patterns, either by promoting excessive division or by causing cell cycle arrest, impacting tissue development and function. - This can be due to the insertion of viral promoters or enhancers near growth-regulating genes. *Latency* - The integrated viral genome can remain dormant within the host chromosome without producing new viral particles for extended periods, a state known as **latency**. - During latency, the virus can be reactivated later to cause a productive infection, as seen with **herpesviruses**.
Question 1340: Von Magnus phenomenon:
- A. Virus has high infectivity
- B. Is a normal replicative cycle
- C. Virus yields have high hemagglutination but low infectivity (Correct Answer)
- D. Virus yield has low hemagglutination
Explanation: ***Virus yields have high hemagglutination but low infectivity*** - The **von Magnus phenomenon** describes the serial passaging of influenza virus at high multiplicity of infection, leading to the production of **defective interfering particles (DIPs)**. - These DIPs retain their ability to **hemagglutinate** (due to intact hemagglutinin proteins) but have lost significant portions of their genome, resulting in **low infectivity**. *Is a normal replicative cycle* - The von Magnus phenomenon is characterized by an **abnormal replicative cycle** and the accumulation of defective viral particles. - A normal replicative cycle involves the production of **fully infectious** viral progeny. *Virus yield has low hemagglutination* - The abnormal particles produced during the von Magnus phenomenon, known as **defective interfering particles (DIPs)**, typically retain their **hemagglutinin protein**. - This allows them to still induce **hemagglutination**, despite their reduced infectivity. *Virus has high infectivity* - A hallmark of the von Magnus phenomenon is the production of virus particles with **significantly reduced infectivity**. - This is due to the deletion or mutation of essential genetic material necessary for a productive infection.
Practice by Chapter
Virus Structure and Classification
Practice Questions
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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