Virology Practice Questions

Q: Which of the following statements about the influenza virus is NOT true?

All types exhibit antigenic shift.. ***All types exhibit antigenic shift.*** - This statement is **incorrect** (and thus the correct answer to this question asking for what is NOT true). - **Antigenic shift** is a major genetic reassortment event that occurs primarily in **Influenza A virus**, where entire gene segments are exchanged between different strains, potentially leading to pandemic strains. - **Influenza B** can undergo antigenic drift but does NOT typically exhibit antigenic shift due to its limited host range (primarily humans) and lack of reassortment opportunities. - **Influenza C** causes mild respiratory illness and shows minimal antigenic variation. *Only type A shows antigenic drift.* - This statement is **false**. Both **Influenza A and Influenza B** undergo **antigenic drift**. - Antigenic drift involves gradual accumulation of point mutations in hemagglutinin (HA) and neuraminidase (NA) genes, allowing immune evasion. - This is why this is also an incorrect statement, but the question asks for one answer, and "all types exhibit shift" is the more clearly false statement. *Drift is the accumulation of point mutations.* - This statement is **true**. - **Antigenic drift** results from **point mutations** in genes encoding surface proteins (HA and NA). - These minor changes allow the virus to evade existing immunity, causing seasonal epidemics. *None of the above.* - This option is incorrect because there IS a false statement among the options ("All types exhibit antigenic shift").

Q: Which paramyxovirus lacks hemagglutinin and neuraminidase but has fusion (F) and attachment (G) proteins?

RSV. ***RSV*** - **Respiratory Syncytial Virus (RSV)** is unique among paramyxoviruses because it **lacks hemagglutinin and neuraminidase** proteins. - Instead, it primarily relies on its **fusion (F) protein** for cell entry and syncytia formation, and an **attachment (G) protein** for binding to host cells. *CMV* - **Cytomegalovirus (CMV)** is a **herpesvirus**, not a paramyxovirus, and therefore has a different array of envelope glycoproteins (gB, gH, gL, gO) essential for cell entry and immune evasion. - It does not possess hemagglutinin, neuraminidase, or the specific F and G proteins characteristic of paramyxoviruses. *HSV* - **Herpes Simplex Virus (HSV)** is also a **herpesvirus**, distinct from paramyxoviruses in its genomic structure and envelope protein composition. - Its envelope contains various glycoproteins, such as **gB, gC, gD, gE, gH, and gL**, which mediate attachment, entry, and cell-to-cell spread, none of which are hemagglutinin, neuraminidase, or the specific F and G proteins mentioned. *Epstein-Barr virus* - **Epstein-Barr virus (EBV)** is another **herpesvirus**, possessing multiple envelope glycoproteins (e.g., gp350/220, gp42, gH, gL) that facilitate its specific entry mechanisms into B lymphocytes and epithelial cells. - Like other herpesviruses, EBV **lacks hemagglutinin and neuraminidase** and does not encode the F and G proteins seen in paramyxoviruses.

Q: The most common cause of sporadic viral encephalitis is what?

Herpes simplex encephalitis. ***Herpes simplex encephalitis*** - **Herpes simplex virus (HSV)**, particularly **HSV-1**, is the most frequent cause of **sporadic viral encephalitis** globally. - It often presents with characteristic temporal lobe involvement, leading to **focal neurological deficits** and **seizures** [1]. *Japanese B encephalitis* - This is a prominent cause of **epidemic viral encephalitis** in Asia, primarily affecting children, but not the most common cause of **sporadic cases**. - It is transmitted by **mosquitoes** and typically has a seasonal pattern. *Human immunodeficiency virus encephalitis* - HIV can cause **encephalopathy** and dementia in advanced stages, but it is not typically characterized as **acute viral encephalitis** [1]. - The neurological manifestations of HIV are more chronic and progressive rather than an acute inflammatory process of the brain [1]. *Rubeola encephalitis* - **Rubeola (measles virus)** can cause acute post-infectious encephalomyelitis or the rare, fatal, late-onset condition **subacute sclerosing panencephalitis (SSPE)**. - While serious, these conditions are not the most common cause of **sporadic acute viral encephalitis** in the general population.

Q: Which one of the following hepatitis viruses has significant perinatal transmission?

Hepatitis B virus. ***Hepatitis B virus*** - **Perinatal transmission** is a major mode of HBV spread, occurring from an infected mother to her baby during birth. - Infants born to HBV-positive mothers have a high risk of developing **chronic HBV infection**, leading to serious liver disease later in life if not properly managed with immunization and immunoglobulin. *Hepatitis E virus* - Primarily transmitted via the **fecal-oral route**, often through contaminated water. - While it can be transmitted vertically, significant **perinatal transmission** leading to chronic outcomes in the infant is not a primary concern compared to HBV. *Hepatitis C virus* - While vertical transmission from mother to child can occur, the rate of **perinatal HCV transmission** is much lower (around 5%) compared to HBV. - It is mainly transmitted through exposure to infected blood, such as via **intravenous drug use** or blood transfusions prior to screening. *Hepatitis A virus* - Transmitted almost exclusively via the **fecal-oral route**, usually through contaminated food or water. - Perinatal transmission is **extremely rare** and does not represent a significant mode of global HAV spread or burden of disease.

Q: Which of the following statements about Hepatitis C virus characteristics is correct?

Antibody to HCV may not be seen in the acute stage. ***Correct: Antibody to HCV may not be seen in the acute stage*** - It takes time for the body to produce a detectable antibody response after **HCV infection**, leading to a **"window period"** where antibodies are negative but the virus is present - During the **acute phase**, diagnosis relies on detecting **HCV RNA** (viral load) rather than antibodies - **Anti-HCV antibodies** typically appear **6-12 weeks** after infection, making early serological diagnosis unreliable *Incorrect: Easy to culture in standard laboratory conditions* - **HCV** is notoriously **difficult to culture** in vitro, which has historically hindered research and drug development - Its **complex viral replication cycle** and **host-specific factors** make standard laboratory culture challenging - This difficulty delayed HCV research until molecular techniques became available *Incorrect: Spreads primarily through respiratory droplets* - **HCV** is primarily transmitted through **blood-to-blood contact**, such as sharing needles, contaminated medical equipment, or blood transfusions - It does not spread through casual contact, food, water, or **respiratory droplets** - Main routes include **intravenous drug use**, **unsafe medical practices**, and historically **blood transfusions** (before screening) *Incorrect: Rarely causes chronic hepatitis* - A high percentage of individuals infected with **HCV (50-85%)** develop **chronic hepatitis**, which can lead to severe liver disease like **cirrhosis** and **hepatocellular carcinoma** - This high chronicity rate makes HCV a significant public health concern - Unlike Hepatitis A and E, HCV has a **strong tendency toward chronicity**

Q: Causative organism of tropical spastic paraparesis is?

HTLV. ***HTLV*** - **Human T-lymphotropic virus type 1 (HTLV-1)** is the definitive causative agent for **tropical spastic paraparesis (TSP)**, also known as **HTLV-1-associated myelopathy (HAM)**. - The virus primarily infects CD4+ T-cells and leads to chronic inflammation and demyelination within the spinal cord, particularly affecting the **thoracic spinothalamic tracts** and **corticospinal tracts**. *HIV 1* - **HIV-1** can cause vacuolar myelopathy, which is a different neurological complication that presents with similar symptoms to TSP but is a direct effect of HIV rather than HTLV-1 infection. - While both can cause myelopathies, **HIV-1** is not the causative agent for tropical spastic paraparesis itself; that is specifically linked to HTLV-1. *HIV 2* - **HIV-2** is less common than HIV-1 and primarily found in West Africa. It can also cause neurological complications, but it is not directly associated with **tropical spastic paraparesis**. - Its neurological manifestations are generally milder and less frequent compared to **HIV-1**, and not classically linked to TSP. *HBV* - **Hepatitis B virus (HBV)** is a hepadnavirus primarily affecting the liver, causing hepatitis, cirrhosis, and hepatocellular carcinoma. - **HBV** is not known to directly cause neurological conditions like tropical spastic paraparesis; its extrahepatic manifestations are typically vasculitis or neuromuscular syndromes, not myelopathy.

Q: Which of the following is the causative agent of rubella?

Caused by RNA virus of Togavirus family. ***Caused by RNA virus of Togavirus family*** - Rubella, also known as German measles, is caused by a **single-stranded RNA virus** belonging to the **Togaviridae family** (specifically the *Rubivirus* genus). - This classification is important for understanding its replication, transmission, and immune response. *There is no known carrier state for postnatally acquired rubella* - This statement is not the causative agent of rubella; it describes a characteristic of the disease's epidemiology. - While prolonged shedding can occur, a true chronic **carrier state** like that seen in certain other viral infections is not characteristic of rubella. *Rubella vaccine is live attenuated with strain RA 27/3* - This describes the **rubella vaccine**, not the causative agent itself. - The **RA 27/3 strain** refers to the specific attenuated (weakened) virus used in the vaccine to induce active immunity. *Risk of transmission and severity maximum in 1st trimester of pregnancy* - This statement describes a crucial clinical aspect of rubella infection in pregnant women, specifically concerning **congenital rubella syndrome (CRS)**, but it does not identify the causative agent. - The risk of **fetal infection** and severe birth defects is highest when the mother contracts rubella during the **first trimester** of pregnancy.

Q: Risk of HIV transmission is not seen with

Plasma derived hepatitis B vaccine. The original text with [1] citations added (ONLY for relevant references) - **Plasma-derived hepatitis B vaccines** undergo extensive purification and inactivation processes, which effectively eliminate the risk of **HIV transmission** [1]. - The manufacturing process ensures that any potential viral contaminants, including HIV, are **inactivated** or removed, making the vaccine safe [1]. *Whole blood* - **Whole blood** transfusions carry a significant risk of **HIV transmission** if the donor is infected and the blood is not properly screened [2]. - HIV can survive in whole blood, making it a direct conduit for transmission from an infected donor to a recipient [1], [2]. *Platelets* - **Platelets** are derived from whole blood and can contain viable **HIV particles**, posing a risk of transmission during transfusion [2]. - Although the risk might be slightly lower than with whole blood due to processing, it is still a recognized route for HIV transmission [1]. *Leukocytes vaccines* - The term "leukocytes vaccines" is vague, but if it refers to products containing **leukocytes** (white blood cells), these cells are a primary host for **HIV**. - Components directly derived from or containing viable leukocytes from an infected individual would carry a high risk of HIV transmission.

Q: What is the causative agent of Adult T-cell Leukemia/Lymphoma (ATLL)?

HTLV-1 (Human T-lymphotropic virus type 1). ***HTLV-1 (Human T-lymphotropic virus type 1)*** - **HTLV-1** is definitively linked to the pathogenesis of **Adult T-cell Leukemia/Lymphoma (ATLL)**, a rare but aggressive form of T-cell malignancy. - The virus **immortalizes** and **transforms CD4+ T-cells**, leading to uncontrolled proliferation and the development of leukemia/lymphoma. *HIV* - **HIV** primarily causes **Acquired Immunodeficiency Syndrome (AIDS)** by targeting CD4+ T-cells, leading to their destruction and systemic immune dysfunction. - While HIV-infected individuals have an increased risk of certain lymphomas, these are typically **B-cell lymphomas** (e.g., diffuse large B-cell lymphoma, primary central nervous system lymphoma) and are linked to immune suppression, not directly caused by HIV transforming T-cells into ATLL. *EBV (Epstein-Barr Virus)* - **EBV** is associated with various **lymphoproliferative disorders** and cancers, often of B-cell origin, such as **Burkitt lymphoma**, Hodgkin lymphoma, and nasopharyngeal carcinoma. - While it infects B-cells and can cause transformation, it is not the causative agent for primary T-cell leukemias like ATLL. *HTLV-2 (Human T-lymphotropic virus type 2)* - **HTLV-2** is related to HTLV-1 but is generally **not associated with malignancy**. - It is implicated in some neurological disorders but has not been shown to cause ATLL or any other T-cell leukemia/lymphoma.

Question 1

Which of the following statements about the influenza virus is NOT true?

Accepted Answer

All types exhibit antigenic shift.

Answer

Drift is the accumulation of point mutations.

Answer

Only type A shows antigenic drift.

Answer

None of the above.

Question 2

Which paramyxovirus lacks hemagglutinin and neuraminidase but has fusion (F) and attachment (G) proteins?

Accepted Answer

RSV

Answer

CMV

Answer

HSV

Answer

Epstein-Barr virus

Question 3

The most common cause of sporadic viral encephalitis is what?

Accepted Answer

Herpes simplex encephalitis

Answer

Japanese B encephalitis

Answer

Human immunodeficiency virus encephalitis

Answer

Rubeola encephalitis

Question 4

Which one of the following hepatitis viruses has significant perinatal transmission?

Accepted Answer

Hepatitis B virus

Answer

Hepatitis E virus

Answer

Hepatitis C virus

Answer

Hepatitis A virus

Question 5

Which of the following statements about Hepatitis C virus characteristics is correct?

Accepted Answer

Antibody to HCV may not be seen in the acute stage

Answer

Easy to culture in standard laboratory conditions

Answer

Spreads primarily through respiratory droplets

Answer

Rarely causes chronic hepatitis

Question 6

Causative organism of tropical spastic paraparesis is?

Accepted Answer

HTLV

Answer

HIV 1

Answer

HIV 2

Answer

HBV

Question 7

Which of the following is the causative agent of rubella?

Accepted Answer

Caused by RNA virus of Togavirus family

Answer

Risk of transmission and severity maximum in 1st trimester of pregnancy

Answer

Rubella vaccine is live attenuated with strain RA 27/3

Answer

There is no known carrier state for postnatally acquired rubella

Question 8

Risk of HIV transmission is not seen with

Accepted Answer

Plasma derived hepatitis B vaccine

Answer

Platelets

Answer

Leukocytes vaccines

Answer

Whole blood

Question 9

What is the causative agent of Adult T-cell Leukemia/Lymphoma (ATLL)?

Accepted Answer

HTLV-1 (Human T-lymphotropic virus type 1)

Answer

EBV (Epstein-Barr Virus)

Answer

HIV

Answer

HTLV-2 (Human T-lymphotropic virus type 2)

Question 10

Which of the following statements about influenza is true?

Accepted Answer

Type-A virus can cause pandemics

Answer

Incubation period is 18-72 hours

Answer

Type-A virus is associated with Reye's syndrome when aspirin is used

Answer

Most infections are subclinical or mild

Virology — MCQs

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