Virology Practice Questions

Q: Which viral infection is most likely responsible for triggering this aplastic crisis in the patient?

Parvovirus B19. ***Parvovirus B19*** - **Parvovirus B19** specifically targets and destroys **red blood cell precursors** in the bone marrow, leading to a temporary cessation of erythropoiesis [1]. - In patients with underlying hemolytic anemias (e.g., **sickle cell disease**, **hereditary spherocytosis**), this temporary aplasia can trigger a severe **aplastic crisis** due to their already shortened red blood cell lifespan [2]. *Epstein-Barr Virus (EBV)* - While EBV can cause various hematologic complications, including some myelosuppression, it is not typically associated with triggering acute **aplastic crises** due to direct erythroid precursor destruction [3]. - EBV is primarily known for causing **infectious mononucleosis** and is linked to lymphoproliferative disorders [3]. *Hepatitis B Virus (HBV)* - HBV infection primarily affects the **liver** and is not a common cause of acute **aplastic crisis** by directly targeting bone marrow hematopoietic cells. - Chronic HBV infection can rarely be associated with **aplastic anemia**, but not usually with an acute crisis. *Cytomegalovirus (CMV)* - CMV can cause myelosuppression, especially in **immunocompromised individuals**, and may lead to pancytopenia. - However, CMV does not typically induce the sudden and severe **erythroid aplasia** characteristic of an aplastic crisis in hemolytic anemia patients, as seen with Parvovirus B19 [1].

Q: A pregnant woman, whose niece contracted varicella while living in the same house, tested negative for serum antibodies to varicella. What does this result indicate?

She is susceptible to chickenpox. ***She is susceptible to chickenpox*** - A negative test for serum antibodies to varicella indicates a **lack of protective immunity** to the varicella-zoster virus (VZV). - This woman has not previously been infected with VZV or vaccinated, making her **susceptible to primary infection (chickenpox)** upon exposure. *She is susceptible to zoster* - **Zoster (shingles)** is caused by the **reactivation of latent VZV** in individuals who have previously had chickenpox. - Since she tested negative for antibodies, she has not had chickenpox and thus **cannot harbor latent VZV** to reactivate. *She is immune to zoster* - Immunity to zoster implies that she has had chickenpox and subsequently developed a robust immune response to prevent viral reactivation. - A negative antibody test directly contradicts this, as it signifies no prior exposure or immune response. *She is immune to chicken pox* - Immunity to chickenpox is established by the presence of **varicella antibodies**, which are absent in this case. - A negative antibody result means she is **not immune** and is therefore at risk of contracting chickenpox if exposed.

Q: A child presented with bluish-white spots in the mouth followed by a rash. What is the genome of the most likely causative agent?

Enveloped virus with single-stranded RNA. ***Enveloped virus with single-stranded RNA*** - Bluish-white spots in the mouth (**Koplik spots**) followed by a rash are pathognomonic for **measles**, which is caused by the **measles virus**. - The measles virus is a **paramyxovirus**, characterized as an **enveloped, negative-sense, single-stranded RNA virus**. *Double stranded Naked RNA* - No major human pathogen belongs to this specific genomic and structural classification. - Most **dsRNA viruses** like **rotavirus** are **naked** but cause gastroenteritis, not measles. *Naked virus with single-stranded RNA* - Viruses like **rhinovirus** (common cold) or **poliovirus** fit this description but do not cause Koplik spots or measles. - **Naked viruses** lack a lipid envelope, making them generally more resistant to environmental factors. *Double stranded Enveloped RNA* - There are no known medically significant human viruses that are both **enveloped** and contain **double-stranded RNA**. - Viral genomes are typically either DNA or RNA, and RNA viruses are usually single-stranded (positive or negative sense) or double-stranded, with or without an envelope.

Q: The viruses of the Filoviridae family like Ebola and Marburg resemble which of the following morphologies?

Filamentous. ***Filamentous*** - Viruses in the **Filoviridae family**, including **Ebola** and **Marburg**, are characterized by their distinct **long, filamentous shape**. - This morphology is a key distinguishing feature visible under electron microscopy, contributing to their namesake ("filo" meaning "thread-like"). *Brick shaped* - **Brick-shaped morphology** is characteristic of **Poxviridae**, such as the **variola virus** (smallpox). - This shape is distinctly different from the thread-like structure of filoviruses. *Bullet shaped* - **Bullet-shaped viruses** are typical of the **Rhabdoviridae family**, which includes the **rabies virus**. - This shape is consistent and easily recognizable for this family, contrasting with the much longer and flexible filaments of filoviruses. *Spherical* - **Spherical morphology** is common among many virus families, including **influenza virus** (Orthomyxoviridae) and **human immunodeficiency virus (HIV)** (Retroviridae). - While many viruses are roughly spherical, filoviruses are specifically known for their elongated, non-spherical appearance.

Q: The following are parvovirus - related disease - population pairs. Identify the incorrect pair. 1. Aplastic anemia - Patient with hereditary hemolytic anemia 2. Non - immune hydrops - pregnant women 3. Erythema infectiosum - infants 4. Non - erosive arthritis - Patients of SLE

4. ***Non - erosive arthritis - Patients of SLE*** - While parvovirus B19 can cause **non-erosive arthritis**, it is not specifically associated with patients with **systemic lupus erythematosus (SLE)** as a common or unique presentation. Parvovirus B19-induced arthritis typically resolves spontaneously. [1] - The given pairing implies a direct and specific link between parvovirus B19 arthritis and SLE patients, which is inaccurate. *Aplastic anemia - Patient with hereditary hemolytic anemia* - This is a **correct pairing**. Parvovirus B19 preferentially infects and destroys erythroid progenitor cells, leading to a temporary cessation of red blood cell production. [1] - In patients with **hereditary hemolytic anemias** (e.g., sickle cell anemia, thalassemia), who have a rapid red blood cell turnover and depend on continuous erythropoiesis, this cessation can lead to a severe and life-threatening **aplastic crisis**. [1] *Non - immune hydrops - pregnant women* - This is a **correct pairing**. Parvovirus B19 infection in a pregnant woman can cross the placenta and infect the fetus. - Fetal infection can cause severe anemia and heart failure, leading to **non-immune hydrops fetalis**, a condition characterized by abnormal fluid accumulation in two or more fetal compartments. *Erythema infectiosum - infants* - This is a **correct pairing**. **Erythema infectiosum**, also known as "fifth disease," is the most common clinical manifestation of parvovirus B19 infection. [1] - It primarily affects **children** (including infants) and is characterized by a "slapped cheek" rash on the face followed by a lacy rash on the trunk and extremities. [1]

Q: Which virus can be identified by a PCR method and is endemic to India?

Chikungunya virus. ***Chikungunya virus*** - The **Chikungunya virus** is a mosquito-borne alphavirus that causes fever, severe joint pain, and rash, and is **endemic to India** and other tropical regions. - Diagnosis is commonly confirmed using **PCR** (polymerase chain reaction) to detect viral RNA in acute samples. *Ebola virus* - The **Ebola virus** causes severe hemorrhagic fever and is primarily prevalent in **Sub-Saharan Africa**, not endemic to India. - While it can be detected by **PCR**, its geographical distribution does not match the endemic criteria for India. *Yellow fever* - **Yellow fever virus** is transmitted by mosquitoes and is endemic to **tropical and subtropical areas of South America and Africa**. - India is not considered an endemic area for yellow fever, though it can be detected by **PCR**. *Hendra virus* - The **Hendra virus** is a zoonotic virus primarily found in **Australia**, transmitted from bats to horses and then to humans. - It is not endemic to India and thus does not fit the criteria of the question.

Q: A 23-year-old woman presents with vulvar ulcers and lymphadenopathy. Testing confirms primary HSV infection. Which of the following statements about HSV antibody development is correct?

IgG antibodies appear 2-3 weeks after infection and persist. ***IgG antibodies appear 2-3 weeks after infection and persist*** - Following primary HSV infection, the body mounts an immune response, with **IgG antibodies** typically becoming detectable approximately **2-3 weeks post-infection**. [1] - These **IgG antibodies** persist for life, providing long-term immunity and serving as a marker of past or latent infection. [1] *IgG appears immediately after infection* - The immune system requires time to generate a robust antibody response, so **IgG antibodies** do not appear immediately following infection. [2] - The initial immune response involves innate immunity and the production of **IgM antibodies** before IgG. [1], [2] *No antibody response occurs* - The body's immune system recognizes the viral antigens and mounts an antibody response to combat the infection. - Absence of an antibody response would imply a complete failure of the adaptive immune system, which is not the case in immunocompetent individuals with primary HSV. [1] *IgM and IgG appear simultaneously at 6 weeks* - **IgM antibodies** are produced earlier in the immune response compared to **IgG**. [2] - While both may be present at 6 weeks, their appearance is not simultaneous, with IgM preceding IgG, and IgG often detectable by 2-3 weeks, not waiting until 6 weeks. [1]

Q: How does HSV establish latency in the host?

Through retrograde axonal transport to dorsal root ganglia. ***Through retrograde axonal transport to dorsal root ganglia*** - HSV establishes latency by traveling via **retrograde axonal transport** from the site of infection to the sensory **dorsal root ganglia (DRG)**. - In the DRG, the virus remains dormant within the neuronal cells, expressing only latency-associated transcripts (LATs) rather than replicating. *By forming spores in epithelial cells* - HSV is a **DNA virus** and does not form spores, which are typically found in bacteria and fungi as survival structures. - While HSV infects epithelial cells initially, its latency phase is established in neurons, not by forming spores in epithelial tissues. *Through persistent viremia* - **Persistent viremia** refers to the continuous presence of viruses in the bloodstream, which is characteristic of some chronic viral infections but not how HSV establishes latency. - HSV latency involves viral DNA remaining dormant within specific neuronal cells, not actively circulating in the blood. *By integrating into host DNA* - While some viruses (like retroviruses) integrate their genetic material into the host genome, **HSV does not integrate its DNA** during latency. - HSV DNA typically remains as an **episome** (a circular, independent piece of DNA) within the nucleus of the infected neuron during latency.

Q: Which type of HSV is most commonly associated with recurrent genital herpes?

HSV-2. ***HSV-2*** - **HSV-2** is the primary cause of **genital herpes** and is significantly more likely to cause recurrent outbreaks than HSV-1 in the genital region. - The virus establishes **latency in sacral ganglia**, leading to frequent reactivation and subsequent genital lesions. *HSV-1* - While **HSV-1** can cause **genital herpes** (often through oral-genital contact), it is more commonly associated with **oral herpes (cold sores)**. - Genital infections caused by HSV-1 tend to recur less frequently and are generally less severe than those caused by HSV-2. *VZV (Varicella-Zoster Virus)* - **VZV** causes **chickenpox** (initial infection) and **shingles** (reactivation), not genital herpes. - It establishes latency in **dorsal root ganglia** and reactivation presents as a dermatomal rash (shingles). *CMV (Cytomegalovirus)* - **CMV** is a common virus that usually causes **asymptomatic infection** in healthy individuals, but can cause severe disease in immunocompromised patients or neonates. - It is not associated with genital lesions or recurrent genital herpes.

Question 1

Which viral infection is most likely responsible for triggering this aplastic crisis in the patient?

Accepted Answer

Parvovirus B19

Answer

Epstein-Barr Virus (EBV)

Answer

Hepatitis B Virus (HBV)

Answer

Cytomegalovirus (CMV)

Question 2

A pregnant woman, whose niece contracted varicella while living in the same house, tested negative for serum antibodies to varicella. What does this result indicate?

Accepted Answer

She is susceptible to chickenpox

Answer

She is susceptible to zoster

Answer

She is immune to zoster

Answer

She is immune to chicken pox

Question 3

A child presented with bluish-white spots in the mouth followed by a rash. What is the genome of the most likely causative agent?

Accepted Answer

Enveloped virus with single-stranded RNA

Answer

Double stranded Naked RNA

Answer

Naked virus with single-stranded RNA

Answer

Double stranded Enveloped RNA

Question 4

The viruses of the Filoviridae family like Ebola and Marburg resemble which of the following morphologies?

Accepted Answer

Filamentous

Answer

Brick shaped

Answer

Bullet shaped

Answer

Spherical

Question 5

The following are parvovirus - related disease - population pairs. Identify the incorrect pair.

1. Aplastic anemia - Patient with hereditary hemolytic anemia
2. Non - immune hydrops - pregnant women
3. Erythema infectiosum - infants
4. Non - erosive arthritis - Patients of SLE

Accepted Answer

4

Answer

1

Answer

2

Answer

3

Question 6

Which virus can be identified by a PCR method and is endemic to India?

Accepted Answer

Chikungunya virus

Answer

Ebola virus

Answer

Yellow fever

Answer

Hendra virus

Question 7

A 23-year-old woman presents with vulvar ulcers and lymphadenopathy. Testing confirms primary HSV infection. Which of the following statements about HSV antibody development is correct?

Accepted Answer

IgG antibodies appear 2-3 weeks after infection and persist

Answer

IgG appears immediately after infection

Answer

No antibody response occurs

Answer

IgM and IgG appear simultaneously at 6 weeks

Question 8

A 35-year-old woman presents with painful genital ulcers that recur every few months. Current examination reveals multiple shallow ulcers on the labia minora. PCR testing is positive for HSV-2. Which of the following best explains the mechanism of viral latency in this condition?

Accepted Answer

Establishment of dormancy in sensory ganglia as episomal DNA

Answer

Immune evasion through antigenic drift

Answer

Persistent viremia

Answer

Integration into host genome

Question 9

How does HSV establish latency in the host?

Accepted Answer

Through retrograde axonal transport to dorsal root ganglia

Answer

By forming spores in epithelial cells

Answer

Through persistent viremia

Answer

By integrating into host DNA

Question 10

Which type of HSV is most commonly associated with recurrent genital herpes?

Accepted Answer

HSV-2

Answer

HSV-1

Answer

VZV (Varicella-Zoster Virus)

Answer

CMV (Cytomegalovirus)

Virology — MCQs

Virology — MCQs

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