Virology Practice Questions

Q: Among the following, which is the smallest virus?

Parvovirus. ***Parvovirus*** - **Parvoviruses** are among the smallest viruses, typically measuring around **18-26 nanometers** in diameter. - They are unique in having a **single-stranded DNA genome**. *Herpes virus* - **Herpesviruses** are relatively large, **double-stranded DNA viruses** with diameters ranging from **150-200 nanometers**. - They are known for establishing **latent infections** in the host. *Adenovirus* - **Adenoviruses** are medium-sized, **non-enveloped, icosahedral viruses** with **double-stranded DNA genomes**, typically 70-90 nanometers in diameter. - They are a common cause of respiratory, gastrointestinal, and ocular infections. *Poxvirus* - **Poxviruses** are exceptionally large and complex viruses, measuring approximately **200-400 nanometers** in length, and are visible under a light microscope. - They have a unique **brick-shaped morphology** and a **double-stranded DNA genome**.

Q: Which of the following is an oncogenic DNA virus primarily associated with lymphoproliferative disorders?

Epstein-Barr Virus (EBV). ***Epstein-Barr Virus (EBV)*** - **EBV** is a DNA virus strongly associated with several **lymphoproliferative disorders**, including **Burkitt lymphoma**, **Hodgkin lymphoma**, and **post-transplant lymphoproliferative disorder (PTLD)**. - It infects **B lymphocytes** and promotes their proliferation, leading to the risk of malignant transformation. *Human Immunodeficiency Virus (HIV)* - **HIV** is an **RNA retrovirus** that causes acquired immunodeficiency syndrome (AIDS), which can lead to an increased risk of various cancers, including lymphomas, but it is not a DNA virus and its primary mechanism of oncogenesis is indirect via immunosuppression. - While HIV is often associated with lymphomas, it does not directly cause lymphoproliferation in the same way **EBV** does; instead, it weakens the immune system, allowing other oncogenic viruses like EBV to cause malignancies. *HTLV* - **Human T-lymphotropic virus (HTLV)** is an **RNA retrovirus** specifically associated with **adult T-cell leukemia/lymphoma**, not primarily B-cell lymphoproliferative disorders. - It is an **RNA virus**, not a DNA virus, and its oncogenic mechanism involves persistent T-cell activation and proliferation. *HBV* - **Hepatitis B virus (HBV)** is a **DNA virus** primarily associated with **hepatocellular carcinoma (HCC)**, a liver cancer. - It is not directly linked to **lymphoproliferative disorders** but rather to chronic liver inflammation and fibrosis, which contributes to liver cancer.

Q: Which virus has a double-stranded RNA with a segmented genome?

Rotavirus. ***Rotavirus*** - Rotavirus possesses a **double-stranded RNA (dsRNA) genome** that is **segmented** into **11 segments**. - This unique genomic structure is characteristic of the *Reoviridae* family, to which Rotavirus belongs. *Influenza* - Influenza virus has a **segmented single-stranded RNA (ssRNA) genome** of negative sense, not double-stranded RNA. - It belongs to the *Orthomyxoviridae* family. *Arenavirus* - Arenaviruses have a **segmented single-stranded RNA (ssRNA) genome** with an **ambisense** polarity, not double-stranded. - Their genome typically consists of two segments. *Bunyavirus* - Bunyaviruses contain a **segmented single-stranded RNA (ssRNA) genome** of negative or ambisense polarity, not double-stranded. - Their genome is typically divided into three segments.

Q: Virus causing oropharyngeal carcinoma?

Human Papillomavirus (HPV). ***Human Papillomavirus (HPV)*** - **HPV** is a well-established cause of **oropharyngeal carcinoma**, particularly HPV type 16. - The virus integrates its DNA into host cells, leading to overexpression of **oncoproteins E6 and E7**, which inactivate tumor suppressor genes like p53 and Rb. *Epstein-Barr Virus (EBV), which is linked to certain head and neck cancers.* - **EBV** is associated with **Nasopharyngeal Carcinoma (NPC)**, not typically oropharyngeal carcinoma. - While both are in the head and neck region, NPC has distinct epidemiology and genetic associations compared to oropharyngeal cancers linked to HPV. *Human T-lymphotropic virus (HTLV), a virus with potential oncogenic properties.* - **HTLV-1** is primarily associated with **Adult T-cell Leukemia/Lymphoma** and HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). - It does not have a recognized role in the causation of oropharyngeal carcinoma. *Human Herpesvirus 8 (HHV-8), implicated in some malignancies.* - **HHV-8** is most famously known as the causative agent of **Kaposi's sarcoma**, primarily affecting immunocompromised individuals. - It is also linked to certain lymphoproliferative disorders but not oropharyngeal carcinoma.

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: 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.

Question 1

Among the following, which is the smallest virus?

Accepted Answer

Parvovirus

Answer

Herpes virus

Answer

Adenovirus

Answer

Poxvirus

Question 2

Which of the following is an oncogenic DNA virus primarily associated with lymphoproliferative disorders?

Accepted Answer

Epstein-Barr Virus (EBV)

Answer

HTLV

Answer

Human Immunodeficiency Virus (HIV)

Answer

HBV

Question 3

Which virus has a double-stranded RNA with a segmented genome?

Accepted Answer

Rotavirus

Answer

Influenza

Answer

Arenavirus

Answer

Bunyavirus

Question 4

Virus causing oropharyngeal carcinoma?

Accepted Answer

Human Papillomavirus (HPV)

Answer

Human T-lymphotropic virus (HTLV)

Answer

Epstein-Barr Virus (EBV)

Answer

Human Herpesvirus 8 (HHV-8)

Question 5

Molluscum contagiosum virus belongs to?

Accepted Answer

Poxviruses

Answer

Herpesviruses

Answer

Picornaviruses

Answer

Adenovirus

Question 6

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 7

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 8

Most common pox virus infection in humans is?

Accepted Answer

Molluscum contagiosum

Answer

Smallpox

Answer

Monkeypox

Answer

Cowpox

Question 9

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

Accepted Answer

Rhinovirus

Answer

Measles

Answer

EBV

Answer

Reovirus

Question 10

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

Virology — MCQs

Virology — MCQs

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