Virology Practice Questions

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 - While historically accurate, this timeframe is outdated with current **4th generation testing protocols**.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 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: What serum markers are indicative of a high level of Hepatitis B virus (HBV) infection?

HBsAg, HBeAg, and HBV DNA. **HBsAg, HBeAg, and HBV DNA** - The presence of **HBsAg** indicates ongoing HBV infection [1], while **HBeAg** signifies active viral replication and high infectivity [1]. - **HBV DNA levels** directly quantify the amount of viral genetic material, providing a direct measure of viral load and disease activity [1]. *HBsAg only* - While **HBsAg** indicates the presence of HBV infection, it doesn't provide a complete picture of viral replication or load [1]. - It doesn't differentiate between active replication and chronic carriage with low viral activity [1]. *HBsAg and HBV DNA* - This combination is better than HBsAg alone, as **HBV DNA** directly measures viral load [1]. - However, it misses **HBeAg**, which is a crucial marker for active viral replication and high infectivity, especially in the early phases of chronic infection [2]. *Anti-HBsAg and HBV DNA* - **Anti-HBsAg** (HBsAb) indicates immunity to HBV, either from vaccination or resolved infection, and its presence suggests the absence of active infection [1]. - Therefore, the co-existence of **Anti-HBsAg** with significant **HBV DNA** levels is contradictory and unlikely to represent a high level of active HBV infection.

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: 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: 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: 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: 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: 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

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 2

Which virus is known to cause latent infections?

Accepted Answer

HBV

Answer

Rubella

Answer

Influenza virus

Answer

Rotavirus

Question 3

What serum markers are indicative of a high level of Hepatitis B virus (HBV) infection?

Accepted Answer

HBsAg, HBeAg, and HBV DNA

Answer

HBsAg only

Answer

HBsAg and HBV DNA

Answer

Anti-HBsAg and HBV DNA

Question 4

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 5

What virus is primarily responsible for causing Exanthema subitum?

Accepted Answer

HHV-6

Answer

HHV-8

Answer

Parvovirus

Answer

Coxsackievirus

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

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

Accepted Answer

Rhinovirus

Answer

Measles

Answer

EBV

Answer

Reovirus

Question 8

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

Accepted Answer

Rotavirus

Answer

Influenza

Answer

Arenavirus

Answer

Bunyavirus

Question 9

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 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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