Virology Practice Questions

Q: How many segments of RNA does the Influenza virus have?

8 segments of single-stranded RNA. ***8 segments of single-stranded RNA*** - The **Influenza virus** is characterized by its segmented genome, which consists of **eight distinct negative-sense single-stranded RNA (ssRNA)** molecules. - This segmentation is crucial for its high mutation rate and ability to undergo **antigenic shift** and **antigenic drift**, leading to new strains. *5 segments of single-stranded RNA* - This option is incorrect because the Influenza virus specifically has **eight segments**, not five. - While it is a single-stranded RNA virus, the number of segments is a key characteristic. *8 segments of double-stranded DNA* - This option is incorrect as Influenza is an **RNA virus**, not a DNA virus, and its genetic material is single-stranded, not double-stranded. - No known influenza viruses have a **double-stranded DNA genome**. *8 segments of single-stranded DNA* - This option is incorrect because Influenza is an **RNA virus**, not a DNA virus. - Its genetic material is composed of **RNA**, specifically negative-sense single-stranded RNA.

Q: Which virus has the highest chance of transmission to the newborn during delivery?

HSV. ***HSV*** - **Herpes Simplex Virus (HSV)** has the **highest transmission rate during vaginal delivery** if the mother has active genital lesions, with transmission rates of **30-50% for recurrent infection** and up to **85-90% for primary infection**. - Neonatal herpes can lead to severe disseminated disease, central nervous system involvement, or mucocutaneous lesions with high morbidity and mortality. - **Cesarean section is indicated** if active lesions are present at the time of labor to prevent transmission. *CMV* - **Cytomegalovirus (CMV)** is primarily transmitted **congenitally (in utero)** rather than during delivery. - While perinatal transmission can occur through cervical secretions or blood during delivery, the rate is **much lower** than HSV and most postnatal transmission occurs through **breastfeeding**. - Intrapartum transmission, when it occurs, generally causes less severe disease compared to congenital infection. *VZV* - **Varicella-Zoster Virus (VZV)** transmission to the newborn occurs primarily when maternal infection develops **within 5 days before to 2 days after delivery**. - This can cause severe neonatal varicella, but the **overall intrapartum transmission rate is lower** than HSV. - Most severe fetal effects occur with **congenital varicella syndrome** (first or second trimester infection). *Rubella* - **Rubella** is almost exclusively transmitted **congenitally during early pregnancy**, leading to **congenital rubella syndrome**. - There is **no significant transmission during delivery** itself. - The critical period for fetal damage is during the first trimester, not at the time of birth.

Q: Exanthema subitum is caused by which virus?

HHV-6. ***HHV-6*** - **Human Herpesvirus 6 (HHV-6)** is the primary cause of **exanthema subitum**, also known as **roseola infantum**. - This viral infection typically affects young children and is characterized by a **high fever** followed by a **maculopapular rash** once the fever subsides. *HIV (Human Immunodeficiency Virus)* - HIV causes **acquired immunodeficiency syndrome (AIDS)**, a condition characterized by a progressive failure of the immune system. - While HIV can cause various skin manifestations, it is not responsible for **exanthema subitum**. *HCV (Hepatitis C Virus)* - HCV is the primary cause of **hepatitis C**, a liver disease that can lead to chronic liver inflammation, cirrhosis, and liver cancer. - Skin manifestations associated with HCV are generally different from exanthema subitum, such as **porphyria cutanea tarda** or **lichen planus**. *HPV (Human Papillomavirus)* - HPV is a group of viruses that cause **warts** (papillomas) and can lead to certain types of **cancers**, including cervical cancer. - It does not cause **exanthema subitum**.

Q: Which of the following viruses is classified as a poxvirus?

Variola. ***Variola virus*** - **Variola virus** is the causative agent of **smallpox**, a historically significant and highly contagious disease. - It belongs to the **Orthopoxvirus** genus within the **Poxviridae family**, characterized by its large, brick-shaped virion and dsDNA genome. *Coxsackie virus* - **Coxsackieviruses** are part of the **Picornaviridae family**, specifically the **Enterovirus** genus. - They are known to cause a range of diseases including **hand-foot-and-mouth disease**, myocarditis, and aseptic meningitis, and are much smaller than poxviruses. *ECHO virus* - **Echoviruses** (Enteric Cytopathic Human Orphan viruses) are also members of the **Picornaviridae family** and the **Enterovirus** genus. - They are associated with diseases such as **aseptic meningitis**, gastroenteritis, and respiratory infections, completely distinct from poxviruses. *HSV (Herpes Simplex Virus)* - **Herpes Simplex Viruses** belong to the **Herpesviridae family**, characterized by a **linear dsDNA genome** and an enveloped icosahedral capsid. - They cause diseases like **oral and genital herpes** and are structurally and genetically distinct from poxviruses.

Q: Coxsackie virus is classified as which type of virus?

Enterovirus. ***Enterovirus*** - **Coxsackie virus** belongs to the genus *Enterovirus* within the family *Picornaviridae*. - Enteroviruses are characterized as **non-enveloped, positive-sense, single-stranded RNA viruses** and typically infect the gastrointestinal tract. *Herpes virus* - Herpes viruses are **enveloped, double-stranded DNA viruses** known for causing latent infections. - Examples include HSV-1 (oral herpes) and VZV (chickenpox), which are distinct from Coxsackie. *Pox virus* - Pox viruses are **large, enveloped, double-stranded DNA viruses** that replicate in the cytoplasm of infected cells. - Smallpox and molluscum contagiosum are caused by pox viruses, which have different genetic and structural characteristics than Coxsackie virus. *Myxovirus* - **Myxovirus** is an older classification that once included viruses now categorized into *Orthomyxoviridae* (e.g., influenza) and *Paramyxoviridae* (e.g., measles, mumps). - These are **enveloped, negative-sense, single-stranded RNA viruses**, a different viral structure and replication strategy compared to Coxsackie virus.

Q: A patient with sore throat has a positive Paul Bunnell test, indicating infectious mononucleosis. The causative organism is?

EBV. ***Correct: EBV*** - The **Paul-Bunnell test** (monospot test) detects **heterophile antibodies**, which are characteristic of acute **Epstein-Barr virus (EBV)** infection. - **EBV** is the primary causative agent of **infectious mononucleosis**, commonly known as "mono." *Incorrect: Adenovirus* - **Adenoviruses** can cause various infections, including **pharyngitis** and **conjunctivitis**, but are not associated with a positive **Paul-Bunnell test** or heterophile antibodies. - While it can cause sore throat, the presence of a **positive Paul-Bunnell test** differentiates it from EBV. *Incorrect: CMV* - **Cytomegalovirus (CMV)** can cause a mononucleosis-like syndrome, but it typically results in a **negative Paul-Bunnell test** (i.e., it is heterophile antibody-negative). - CMV mononucleosis is often seen in individuals who are **immunocompromised** or in infants as a congenital infection. *Incorrect: HSV (Herpes Simplex Virus)* - **Herpes simplex virus (HSV)** causes infections such as **oral herpes (cold sores)** and **genital herpes**, and in some cases, **pharyngitis**. - HSV infection is not associated with a positive **Paul-Bunnell test** or the production of heterophile antibodies.

Q: Which poxvirus does not grow in eggs or animal cells?

Molluscum contagiosum. ***Molluscum contagiosum*** - This poxvirus is unique among human poxviruses as it **cannot be propagated in cell culture** or embryonated eggs. - It specifically replicates in **human epidermal cells**, causing characteristic skin lesions. *Cow pox* - Cowpox virus can be readily grown in **cell cultures** (e.g., Vero cells) and in **embryonated eggs**, where it produces pocks on the chorioallantoic membrane (CAM). - It is known for its ability to **infect a wide range of host cells and animals**. *Vaccinia* - Vaccinia virus is a widely studied poxvirus that grows efficiently in various **mammalian cell lines** (e.g., Hela, Vero cells) and on the **chorioallantoic membrane of embryonated eggs**. - Its broad host range and ease of culture make it a popular **viral vector** for research and vaccine development. *Variola* - Variola virus, the causative agent of smallpox, was successfully propagated in **cell cultures** (e.g., primary human embryonic kidney cells) and in **embryonated chicken eggs**, producing characteristic pock lesions. - Its ability to grow in these systems was crucial for **vaccine production** and research before its eradication.

Q: Virus quantification is done by-

Plaque assay. ***Plaque assay*** - The **plaque assay** is a widely used and quantitative method to determine the number of **infectious viral particles** in a sample. - It involves infecting a monolayer of host cells with serially diluted virus samples, leading to the formation of visible **plaques** (zones of lysed cells), which are then counted. *Studying virus-cell interactions* - Studying **virus-cell interactions** helps understand the mechanisms of viral entry, replication, and egress but does not directly quantify the number of viral particles. - While critical for understanding viral pathogenesis, this approach is qualitative rather than quantitative in nature. *Visualizing virus particles* - **Visualizing virus particles** (e.g., using electron microscopy) allows for counting individual virions, but it quantifies both infectious and non-infectious particles. - This method provides a total particle count rather than a measure of infectivity. *Virus isolation using eggs* - **Virus isolation using eggs** (e.g., embryonated chicken eggs) is a method for propagating and isolating certain viruses, particularly influenza. - While it can be optimized for relative comparisons, it is not primarily a direct quantitative method like the plaque assay for determining infectious viral titers.

Q: Bollinger bodies are seen in ?

Fowlpox. **IMPORTANT NOTE:** In **human pathology**, the term "Bollinger bodies" classically refers to **sulfur granules** seen in **actinomycosis** (Actinomyces infection), which appear as basophilic masses with radiating eosinophilic clubs. However, this question uses the **veterinary pathology** definition, where Bollinger bodies refer to viral inclusions in avian diseases. ***Fowlpox*** - In **veterinary pathology**, **Bollinger bodies** are characteristic large, eosinophilic **intracytoplasmic inclusion bodies** found in cells infected with the **fowlpox virus** (avipoxvirus). - These inclusions are visible under light microscopy and are a diagnostic feature of **fowlpox**, a widespread avian disease. - Note: Fowlpox is **not a human disease** but affects birds. *Chickenpox* - Chickenpox, caused by the **varicella-zoster virus (VZV)**, is characterized by **intranuclear inclusion bodies** (Cowdry type A) [1]. - It does not form **Bollinger bodies**. *Cowpox* - Cowpox is caused by the **cowpox virus**, an **orthopoxvirus**, and produces **A-type cytoplasmic inclusion bodies** (A-type inclusions). - While these are cytoplasmic inclusions, they are not referred to as **Bollinger bodies**. *Smallpox* - Smallpox, caused by the **variola virus** (orthopoxvirus), is associated with **Guarnieri bodies**, which are **cytoplasmic inclusion bodies**. - These inclusions are distinct from **Bollinger bodies**. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Infectious Diseases, pp. 366-367.

Q: Which of the following statements about p24 is false?

Cannot be detected after seroconversion. ***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 1

How many segments of RNA does the Influenza virus have?

Accepted Answer

8 segments of single-stranded RNA

Answer

5 segments of single-stranded RNA

Answer

8 segments of double-stranded DNA

Answer

8 segments of single-stranded DNA

Question 2

Which virus has the highest chance of transmission to the newborn during delivery?

Accepted Answer

HSV

Answer

CMV

Answer

VZV

Answer

Rubella

Question 3

Exanthema subitum is caused by which virus?

Accepted Answer

HHV-6

Answer

HCV

Answer

HPV

Answer

HIV

Question 4

Which of the following viruses is classified as a poxvirus?

Accepted Answer

Variola

Answer

Coxsackie

Answer

ECHO

Answer

HSV

Question 5

Coxsackie virus is classified as which type of virus?

Accepted Answer

Enterovirus

Answer

Pox virus

Answer

Myxovirus

Answer

Herpes virus

Question 6

A patient with sore throat has a positive Paul Bunnell test, indicating infectious mononucleosis. The causative organism is?

Accepted Answer

EBV

Answer

Adenovirus

Answer

CMV

Answer

HSV (Herpes Simplex Virus)

Question 7

Which poxvirus does not grow in eggs or animal cells?

Accepted Answer

Molluscum contagiosum

Answer

Cow pox

Answer

Vaccinia

Answer

Variola

Question 8

Virus quantification is done by-

Accepted Answer

Plaque assay

Answer

Studying virus-cell interactions

Answer

Visualizing virus particles

Answer

Virus isolation using eggs

Question 9

Bollinger bodies are seen in ?

Accepted Answer

Fowlpox

Answer

Chickenpox

Answer

Cowpox

Answer

Smallpox

Question 10

Which of the following statements about p24 is false?

Accepted Answer

Cannot be detected after seroconversion

Answer

Cannot be seen in the first week

Answer

All of the above

Answer

Can be detected after 3 weeks of infection

Virology — MCQs

Virology — MCQs

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