Virology Practice Questions

Q: Which is the most common influenza virus type causing disease in humans?

Type A. ***Type A*** - **Influenza A virus** is responsible for the majority of human influenza cases and is the only type known to cause **pandemics**. - Its ability to undergo **antigenic shift** results in new viral subtypes that can evade existing immunity, leading to widespread outbreaks. *Type B* - **Influenza B virus** causes regional epidemics, but its genetic variability is less pronounced than Type A, meaning it does not typically cause pandemics. - While it can cause significant illness and fatalities, especially in young children and the elderly, it is generally less common than influenza A. *Type C* - **Influenza C virus** is generally associated with very mild respiratory illnesses and is not thought to cause epidemics or pandemics. - Infections are usually asymptomatic or cause only minor cold-like symptoms. *Type D* - **Influenza D virus** primarily affects pigs and cattle and is not known to cause disease in humans. - It is distinct from human influenza viruses and does not contribute to human influenza seasonal outbreaks.

Q: Which of the following sexually transmitted infections is caused by a retrovirus?

Human Immunodeficiency Virus (HIV). ***Human Immunodeficiency Virus (HIV)*** - HIV is a **retrovirus** characterized by its use of the enzyme **reverse transcriptase** to convert its RNA genome into DNA. - This viral DNA then integrates into the host cell's genome, leading to a persistent infection and eventual immune system compromise. *Human Papillomavirus (HPV)* - HPV is a **DNA virus** responsible for causing warts and is associated with various cancers, particularly cervical cancer. - It replicates within the nucleus of host cells without utilizing reverse transcriptase. *Hepatitis B Virus (HBV)* - While HBV has a complex replication cycle involving reverse transcription, it is classified as a **hepadnavirus**, not a retrovirus. - Its genome is partially double-stranded DNA, and reverse transcription is used to produce DNA from an RNA intermediate during replication. *Herpes Simplex Virus (HSV)* - HSV is a **DNA virus** belonging to the Herpesviridae family, known for causing oral and genital lesions. - It replicates its DNA genome directly within the host cell nucleus and does not involve reverse transcriptase.

Q: What virus is primarily responsible for causing Exanthema subitum?

HHV-6. ***HHV-6*** - **Human Herpesvirus 6 (HHV-6)** is the primary causative agent of **Exanthema subitum**, also known as **Roseola infantum**. - This virus typically infects infants and young children, leading to a high fever followed by a characteristic rash. *HHV-8* - **Human Herpesvirus 8 (HHV-8)** is primarily associated with **Kaposi's sarcoma**, a cancer that affects individuals with weakened immune systems. - It is not implicated in Exanthema subitum. *Parvovirus* - **Parvovirus B19** causes **Fifth disease** (Erythema infectiosum), characterized by a "slapped cheek" rash. - Its clinical presentation, including the rash distribution and timing relative to fever, differs from Exanthema subitum. *Coxsackievirus* - **Coxsackievirus** is responsible for **Hand-foot-and-mouth disease** and herpangina, which involve rashes and lesions primarily on the hands, feet, and mouth or throat. - Exanthema subitum does not typically present with these specific dermatological features.

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 virus is known to cause latent infections?

HBV. ***HBV*** - Among the options listed, **Hepatitis B virus (HBV)** is the best answer, though it's important to note that HBV causes **chronic infection** rather than true **latent infection**. - In chronic HBV infection, the virus persists in hepatocytes with ongoing low-level replication for years to decades, and viral DNA can integrate into the host genome. - **True latent infections** are classically caused by **herpesviruses** (HSV, VZV, EBV, CMV), where viral genomes remain dormant in neurons or lymphocytes with NO active replication until reactivation. - HBV's persistence and potential for reactivation (especially with immunosuppression) makes it the most appropriate choice among these options. *Rubella* - Rubella virus causes a **self-limiting acute infection** that resolves completely within weeks. - After clearance, individuals develop **lifelong immunity** through antibodies, but the virus does not persist in the body. - No latent or chronic infection occurs. *Influenza virus* - Influenza viruses cause **acute respiratory infections** that resolve within 1-2 weeks. - The virus is completely **cleared from the body** after the immune response. - No latency or chronicity is established. *Rotavirus* - Rotavirus causes **acute gastroenteritis** lasting 3-8 days. - The virus is eliminated from the body after the acute illness resolves. - Does not establish persistent, chronic, or latent infections.

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.

Question 1

Which is the most common influenza virus type causing disease in humans?

Accepted Answer

Type A

Answer

Type B

Answer

Type C

Answer

Type D

Question 2

Which of the following sexually transmitted infections is caused by a retrovirus?

Accepted Answer

Human Immunodeficiency Virus (HIV)

Answer

Hepatitis B Virus (HBV)

Answer

Human Papillomavirus (HPV)

Answer

Herpes Simplex Virus (HSV)

Question 3

What virus is primarily responsible for causing Exanthema subitum?

Accepted Answer

HHV-6

Answer

HHV-8

Answer

Parvovirus

Answer

Coxsackievirus

Question 4

Among the following, which is the smallest virus?

Accepted Answer

Parvovirus

Answer

Herpes virus

Answer

Adenovirus

Answer

Poxvirus

Question 5

Which virus is known to cause latent infections?

Accepted Answer

HBV

Answer

Rubella

Answer

Influenza virus

Answer

Rotavirus

Question 6

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 7

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

Accepted Answer

Rotavirus

Answer

Influenza

Answer

Arenavirus

Answer

Bunyavirus

Question 8

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 9

Molluscum contagiosum virus belongs to?

Accepted Answer

Poxviruses

Answer

Herpesviruses

Answer

Picornaviruses

Answer

Adenovirus

Question 10

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

Accepted Answer

P gene

Answer

S gene

Answer

C gene

Answer

X gene

Virology — MCQs

Virology — MCQs

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