Virology Practice Questions

Q: Molluscum contagiosum virus belongs to?

Poxviruses. ***Poxviruses*** - Molluscum contagiosum virus (MCV) is a **DNA virus** belonging to the **Poxviridae family**, genus Molluscipoxvirus. - Poxviruses are among the **largest and most complex viruses**, with a characteristic **brick-shaped or ovoid morphology**. - MCV causes **cutaneous lesions** characterized by smooth, pearly, dome-shaped papules with central umbilication. - Unlike other poxviruses, MCV replicates exclusively in the **cytoplasm** and causes a benign, self-limiting skin infection. *Herpesviruses* - Herpesviruses are also **DNA viruses** (e.g., HSV, VZV, EBV) but belong to the Herpesviridae family. - They are characterized by their ability to establish **lifelong latency** in neurons or lymphocytes. - They have an **icosahedral capsid** with an envelope, distinct from the brick-shaped morphology of poxviruses. - They typically cause vesicular lesions, not the umbilicated papules seen with MCV. *Picornaviruses* - Picornaviruses are **small, non-enveloped RNA viruses** (e.g., poliovirus, coxsackievirus, enteroviruses). - Their name reflects their small size ("pico" = small) and RNA genome. - Their genetic material is **positive-sense single-stranded RNA**, fundamentally different from the DNA genome of MCV. - They cause diverse infections including poliomyelitis, hand-foot-and-mouth disease, and the common cold. *Adenovirus* - Adenoviruses are **non-enveloped, double-stranded DNA viruses** with an **icosahedral capsid**. - They commonly cause respiratory infections, conjunctivitis, and gastroenteritis. - While they are DNA viruses, their morphology, replication strategy, and disease manifestations are distinct from the cutaneous lesions caused by MCV.

Q: DNA polymerase of HBV is encoded by which of the following ?

P gene. ***P gene*** - The **P gene** (polymerase gene) of the **Hepatitis B virus (HBV)** encodes for the viral DNA polymerase. - This enzyme is crucial for HBV replication, as it functions as both a **reverse transcriptase** and a **DNA-dependent DNA polymerase**. *S gene* - The **S gene** encodes for the **surface antigens (HBsAg)** of HBV, which are involved in viral entry and are the primary targets of the host immune response. - It does not encode for the viral polymerase. *C gene* - The **C gene** encodes for the **HBV core antigen (HBcAg)**, which forms the viral nucleocapsid. - It also produces the **e antigen (HBeAg)**, which is a secreted protein indicating active viral replication. *X gene* - The **X gene** encodes for the **HBV X protein (HBxAg)**, which is a regulatory protein involved in viral transcription and replication. - It plays a role in **hepatocarcinogenesis** but does not encode the polymerase enzyme.

Q: What is the window period in HIV infection?

2-4 weeks. ***2-4 weeks*** - The **window period** in HIV infection is the time between initial infection and when a **detectable immune response** can be measured by standard testing. - Modern **4th generation Ag/Ab combination tests** (now standard in most settings) detect both **HIV p24 antigen** and **HIV antibodies**, reducing the window period to **18-45 days (approximately 2-4 weeks)**. - During this phase, individuals are highly infectious, and early testing with 4th generation tests provides the earliest reliable detection. - **HIV RNA/PCR tests** can detect even earlier (10-14 days) but are not routinely used for initial screening. *4-8 weeks* - This represents the window period for **older 3rd generation antibody-only tests**, which are no longer the standard screening method in most clinical settings. - While historically accurate, this timeframe is outdated with current **4th generation testing protocols**. *8-12 weeks* - This extended period may apply to some **point-of-care rapid tests** or in cases with delayed seroconversion, but exceeds the typical window for standard laboratory-based 4th generation tests. - Most individuals will have detectable antibodies well before this timeframe with modern testing. *> 12 weeks* - By this point, nearly all infected individuals would have developed detectable antibodies with any test generation. - A negative test after 12 weeks essentially **rules out HIV infection** (assuming no recent high-risk exposures). - This is well beyond the **window period** for all standard HIV testing methods.

Q: Which paramyxovirus does not have hemagglutinin and neuraminidase but has a membrane fusion protein?

RSV. ***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.

Q: Most common pox virus infection in humans is?

Molluscum contagiosum. ***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.

Q: Which of the following viruses does not typically cause viral hepatitis?

Rhinovirus. ***Rhinovirus*** - **Rhinoviruses** are the primary cause of the common cold, affecting the **upper respiratory tract**, and are not known to typically cause hepatitis. - They replicate optimally at lower temperatures found in the nasal passages, rather than the higher temperatures of internal organs like the liver. *Measles* - The **measles virus** (rubeola) can cause **transaminitis** and, in rare severe cases, can lead to hepatitis as part of a systemic infection. - While not its primary target, liver inflammation can occur in connection with measles. *EBV* - **Epstein-Barr virus (EBV)** is a common cause of **infectious mononucleosis** and frequently causes **mild, self-limiting hepatitis**, characterized by elevated liver enzymes. - In some cases, EBV can lead to more significant or prolonged hepatitis, especially in immunocompromised individuals. *Reovirus* - **Reoviruses** can cause a range of infections, including **gastroenteritis** and respiratory illnesses, and are known to cause hepatitis in infants and immunocompromised individuals. - While not as common as other hepatitis viruses, reoviruses can lead to liver inflammation.

Q: A child presents with a fever and a rash. Urine examination showed cells with owl's eye appearance. What is the most likely diagnosis?

Cytomegalovirus (CMV) infection. ***Cytomegalovirus (CMV) infection*** - The presence of cells with an **owl's eye appearance** in urine sediment is a classic histological hallmark of **CMV infection**. - CMV can cause a variety of symptoms in children, including **fever and rash**, making this the most likely diagnosis. *Herpes simplex virus infection* - HSV causes characteristic **vesicular lesions** on mucocutaneous surfaces, often associated with fever. - While HSV can cause systemic illness, it does not typically present with **owl's eye inclusions** in urine cells. *Toxoplasmosis caused by Toxoplasma gondii* - **Toxoplasmosis** can cause fever and rash, especially in congenital infections or immunocompromised individuals. - However, it does not lead to **owl's eye inclusions** in urinary cells, which are pathognomonic for CMV. *Infectious mononucleosis caused by Epstein-Barr virus* - **Infectious mononucleosis** commonly presents with fever, fatigue, and lymphadenopathy, sometimes with a rash. - **Epstein-Barr virus (EBV)** infection does not produce cells with an **owl's eye appearance** in the urine; that is specific to CMV.

Q: A patient complains about painful blisters around the angle of mouth, identify the pathogen

Herpes Simplex Virus type 1 (HSV-1). ***Herpes Simplex Virus type 1 (HSV-1)*** - HSV-1 is the primary cause of **oral herpes**, commonly presenting as **cold sores** or **fever blisters** around the mouth [1]. - The characteristic painful blisters at the angle of the mouth are typical of **recurrent HSV-1 infection** [1]. *Coxsackievirus* - Coxsackievirus primarily causes **hand-foot-and-mouth disease** or **herpangina**, characterized by lesions on the hands, feet, and inside the mouth/throat, not typically painful blisters around the external angle of the mouth [2]. - It often presents with a **rash** and **fever** in children [2]. *Epstein-Barr Virus* - Epstein-Barr Virus (EBV) is the causative agent of **infectious mononucleosis**, which presents with **fatigue**, **fever**, **sore throat**, and **lymphadenopathy**. - It does not typically cause painful blisters around the mouth. *Varicella-Zoster Virus* - Varicella-Zoster Virus (VZV) causes **chickenpox** (primary infection) and **shingles** (reactivation) [3]. - While shingles can cause painful blisters, it typically follows a **dermatomal distribution** and is not localized to the angle of the mouth in this manner [3].

Q: Which viral infection is known to cause a condition resembling erythroblastosis?

Parvovirus B19. ***Parvovirus B19*** - **Parvovirus B19** has a specific tropism for **erythroid progenitor cells** in the bone marrow. - In the fetus, congenital infection causes **severe anemia** due to destruction of red blood cell precursors, leading to **hydrops fetalis** with massive compensatory erythropoiesis. - This results in circulating **nucleated red blood cells (erythroblasts)**, hepatosplenomegaly from extramedullary hematopoiesis, and severe anemia - a picture closely **resembling erythroblastosis fetalis**. - Unlike the immune-mediated hemolysis in Rh isoimmunization, parvovirus causes direct viral destruction of erythroid precursors with similar clinical manifestations. *CMV* - **Cytomegalovirus (CMV)** is the most common congenital infection and can cause hepatosplenomegaly, jaundice, and thrombocytopenia. - However, CMV typically causes **direct hyperbilirubinemia** from hepatocellular damage rather than the hemolytic anemia pattern seen in erythroblastosis. - While CMV can affect hematopoiesis, it does not characteristically produce the massive erythroblast response and hydrops pattern typical of erythroblastosis fetalis. *EBV* - **Epstein-Barr virus (EBV)** primarily causes **infectious mononucleosis** in older children and adults, with atypical lymphocytosis. - EBV is rare in neonates and does not cause fetal hydrops or an erythroblastosis-like syndrome. - Associated with lymphoproliferative disorders and post-transplant complications rather than fetal anemia. *HSV* - **Herpes simplex virus (HSV)** causes disseminated neonatal infection with encephalitis, hepatitis, and mucocutaneous lesions. - HSV does not have tropism for erythroid precursors and does not cause the anemia, hydrops, or erythroblastosis-like picture. - Typically acquired perinatally rather than causing congenital infection with hematologic manifestations.

Q: Rubella virus belongs to which family?

Togavirus. ***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 1

Molluscum contagiosum virus belongs to?

Accepted Answer

Poxviruses

Answer

Herpesviruses

Answer

Picornaviruses

Answer

Adenovirus

Question 2

DNA polymerase of HBV is encoded by which of the following ?

Accepted Answer

P gene

Answer

S gene

Answer

C gene

Answer

X gene

Question 3

What is the window period in HIV infection?

Accepted Answer

2-4 weeks

Answer

> 12 weeks

Answer

8-12 weeks

Answer

4-8 weeks

Question 4

Which paramyxovirus does not have hemagglutinin and neuraminidase but has a membrane fusion protein?

Accepted Answer

RSV

Answer

Measles

Answer

Parainfluenza

Answer

Mumps

Question 5

Most common pox virus infection in humans is?

Accepted Answer

Molluscum contagiosum

Answer

Smallpox

Answer

Monkeypox

Answer

Cowpox

Question 6

Which of the following viruses does not typically cause viral hepatitis?

Accepted Answer

Rhinovirus

Answer

Measles

Answer

EBV

Answer

Reovirus

Question 7

A child presents with a fever and a rash. Urine examination showed cells with owl's eye appearance. What is the most likely diagnosis?

Accepted Answer

Cytomegalovirus (CMV) infection

Answer

Herpes simplex virus infection

Answer

Toxoplasmosis caused by Toxoplasma gondii

Answer

Infectious mononucleosis caused by Epstein-Barr virus

Question 8

A patient complains about painful blisters around the angle of mouth, identify the pathogen

Accepted Answer

Herpes Simplex Virus type 1 (HSV-1)

Answer

Coxsackievirus

Answer

Epstein-Barr Virus

Answer

Varicella-Zoster Virus

Question 9

Which viral infection is known to cause a condition resembling erythroblastosis?

Accepted Answer

Parvovirus B19

Answer

EBV

Answer

CMV

Answer

HSV

Question 10

Rubella virus belongs to which family?

Accepted Answer

Togavirus

Answer

Orthomyxovirus

Answer

Rheovirus

Answer

Picornavirus

Virology — MCQs

Virology — MCQs

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