Virology Practice Questions

Q: Monkeypox, a viral zoonotic disease, is caused by

a double-stranded DNA virus. ***a double-stranded DNA virus*** - Monkeypox is caused by the **monkeypox virus (MPXV)**, which belongs to the **Poxviridae family**. - Viruses in the Poxviridae family are known for having a **double-stranded DNA genome**. *a single-stranded RNA virus* - Many common viruses, such as **SARS-CoV-2 (COVID-19)**, **influenza virus**, and **HIV**, are single-stranded RNA viruses. - This genomic structure is fundamentally different from that of the monkeypox virus. *a single-stranded DNA virus* - Viruses like **Parvovirus B19** are single-stranded DNA viruses. - This type of genome is less common in human pathogens compared to double-stranded DNA or RNA viruses. *a double-stranded RNA virus* - Viruses such as **rotaviruses**, which cause gastroenteritis, are double-stranded RNA viruses. - While also double-stranded, its RNA nature distinguishes it from the DNA genome of monkeypox virus.

Q: Consider the following statements regarding dengue virus : 1. It has four distinct serotypes. 2. Infection with any one serotype confers lifelong immunity for that virus serotype. 3. Secondary infection with dengue serotype 2 leads to severe form of dengue. Which of the statements given above are correct?

1 and 2 only. ***1 and 2 only*** - Dengue virus indeed has **four distinct serotypes (DENV-1, DENV-2, DENV-3, DENV-4)**, explaining different epidemiological patterns and reinfections. - Infection with one serotype provides **lifelong homologous immunity** against that specific serotype, meaning a person will not get sick again from the same serotype. *2 and 3 only* - While statement 2 is correct, statement 3 is not universally true, as severe dengue can occur with secondary infection of any serotype, although **DENV-2** and **DENV-3** are more frequently implicated. - This option incorrectly excludes the fact that dengue has four distinct serotypes, which is a fundamental aspect of its biology and epidemiology. *1 and 3 only* - While statement 1 is correct, statement 3 is a simplification; severe dengue in secondary infections is due to **antibody-dependent enhancement (ADE)**, which can happen with various heterologous serotypes, not exclusively DENV-2. - This option incorrectly implies that infection with one serotype does not confer lifelong immunity to that specific serotype, which is a key characteristic of dengue immunity. *1, 2 and 3* - This option is incorrect because statement 3, while partially true, is too absolute. Severe dengue can be linked to **DENV-2** or **DENV-3** in secondary infections but isn't exclusive to DENV-2. - The risk of severe dengue is due to a **secondary infection** with a **heterologous serotype**, not specifically serotype 2, though DENV-2 often causes more severe illness in secondary infections.

Q: Which one of the following is a characteristic of Human Immunodeficiency Virus (HIV)?

It is easily killed by heat. ***It is easily killed by heat*** - HIV is an **enveloped RNA virus** that is highly susceptible to inactivation by heat, typically at **56-60°C for 30 minutes**. - This characteristic is important for **sterilization of medical equipment** and understanding the environmental stability of the virus. - Heat lability is a key feature of enveloped viruses due to disruption of the lipid envelope. *It is easily killed by T4 lymphocytes* - **CD4+ T lymphocytes (T4 cells)** are the primary **target cells** for HIV, meaning the virus infects and ultimately destroys them. - HIV evades the immune system and **replicates within** these cells, leading to progressive immunodeficiency. - The virus is NOT killed by T4 cells; rather, it uses them for replication and destroys them in the process. *It cannot cross blood brain barrier* - HIV is known to **cross the blood-brain barrier (BBB)** early in infection, leading to neurological complications. - Presence of HIV in the central nervous system contributes to conditions like **HIV-associated neurocognitive disorder (HAND)** and HIV encephalopathy. - Infected macrophages and monocytes serve as "Trojan horses" carrying the virus across the BBB. *It is resistant to acetone* - HIV is an **enveloped virus**, and its lipid envelope is **susceptible to dissolution by lipid solvents** such as acetone, alcohol, and detergents. - This property makes HIV vulnerable to inactivation by common disinfectants and explains its poor environmental stability. - The envelope is essential for viral entry, so its disruption renders the virus non-infectious.

Q: Consider the following hepatitis viruses : 1. Hepatitis A 2. Hepatitis B 3. Hepatitis C 4. Hepatitis E Which of the above can be commonly transmitted through the faeco-oral route?

1 and 4. ***Correct Answer: 1 and 4*** * Hepatitis A virus (**HAV**) and Hepatitis E virus (**HEV**) are primarily transmitted via the **faecal-oral route**, typically through contaminated food or water. * These infections are often acute and self-limiting, causing symptoms like jaundice, fatigue, and nausea. * HAV is more common in areas with poor sanitation, while HEV often causes waterborne outbreaks, particularly in developing countries. *Incorrect: 1 and 3 only* * While **Hepatitis A** is transmitted faecal-orally, **Hepatitis C** is primarily transmitted through blood-to-blood contact, such as sharing needles or contaminated blood transfusions. * Hepatitis C rarely, if ever, spreads via the faecal-oral route. *Incorrect: 2, 3 and 4* * **Hepatitis B** and **Hepatitis C** are transmitted through parenteral routes (e.g., blood, sexual contact, perinatal transmission), not via the faecal-oral route. * Although Hepatitis E is faecal-orally transmitted, including B and C makes this option incorrect. *Incorrect: 1, 2 and 3* * **Hepatitis A** is transmitted faecal-orally, but **Hepatitis B** and **Hepatitis C** are primarily transmitted through blood and body fluids (parenteral route). * This option incorrectly includes Hepatitis B and C in the faecal-oral transmission category.

Q: Which is the most specific causative agent of Rabies?

Rabies lyssavirus (RABV). ***Rabies lyssavirus (RABV)*** - **Rabies lyssavirus (RABV)**, also known as the **classical rabies virus** or **genotype 1**, is the primary and most specific causative agent of rabies in humans and animals worldwide. - While other lyssaviruses (Lagos bat, Mokola, Duvenhage, Australian bat lyssavirus, etc.) can cause rabies-like illnesses, **RABV is overwhelmingly responsible** for the vast majority of documented rabies cases globally. - It is transmitted primarily through dog bites in endemic regions and causes acute, progressive, fatal encephalomyelitis. *Lagos bat lyssavirus (LBV)* - **Lagos bat lyssavirus (genotype 2)** is a distinct species within the *Lyssavirus* genus that can cause rabies-like disease, primarily in bats in Africa. - It is **rarely associated with human rabies** and is not the most common or specific cause globally. *Mokola lyssavirus (MOKV)* - **Mokola lyssavirus (genotype 3)** is another lyssavirus found in Africa, isolated from shrews, rodents, and rarely humans. - Although it can cause a fatal encephalomyelitis similar to rabies, human cases are **extremely rare**, and it is not considered the typical rabies virus. *Duvenhage lyssavirus (DUVV)* - **Duvenhage lyssavirus (genotype 4)** is a bat-associated lyssavirus found in Africa, first isolated in 1970. - Human cases are **exceptionally rare** (only a few documented cases), and it is not the primary causative agent of classic rabies.

Q: A patient presents with genital grouped vesicles, as shown in the image. What is the most likely causative organism?

Herpes simplex virus. ***Herpes*** - The image shows **grouped vesicles** on an erythematous base, which is the classic presentation of **genital herpes** caused by the **Herpes simplex virus (HSV)**. - These lesions are typically painful and can recur, indicating a viral etiology. *Haemophilus* - *Haemophilus ducreyi* causes **chancroid**, which presents as **painful genital ulcers** with ragged borders and often associated with inguinal lymphadenopathy. - It does not present as grouped vesicles. *Klebsiella* - *Klebsiella granulomatis* causes **donovanosis (granuloma inguinale)**, characterized by progressive, **painless ulcerative lesions** that are highly vascular and bleed easily. - This organism does not cause vesicular lesions. *Treponema* - *Treponema pallidum* causes **syphilis**, which in its primary stage presents as a **painless chancre** (a solitary ulcer) or in secondary stage as a diffuse rash. - It does not cause grouped vesicles.

Q: How does the presence of STIs increase the risk of HIV transmission?

By disrupting mucosal barriers and causing inflammation. ***By disrupting mucosal barriers and causing inflammation*** - Many STIs, particularly those causing **genital ulcers** (e.g., herpes, syphilis) or inflammation (e.g., gonorrhea, chlamydia), disrupt the integrity of the **mucosal barriers** in the genital tract. This provides easier entry points for HIV, as the epithelial cells act as a physical barrier. - The inflammatory response triggered by STIs leads to the recruitment of **HIV target cells** (CD4+ T-cells and macrophages) to the site of infection, increasing their concentration in genital secretions and making them more accessible to HIV during exposure. *By direct enhancement of HIV replication* - While some inflammatory cytokines can enhance HIV replication in vitro, this is not the primary or most significant mechanism by which STIs increase transmission risk in vivo. - The main mechanism involves increased exposure to target cells and disrupted barriers rather than direct viral replication enhancement. *By increasing CD4 receptor density on target cells* - STIs do not demonstrably increase the density of **CD4 receptors** on the surface of individual target cells. - Instead, they increase the *number* of available CD4+ target cells at the site of exposure due to inflammation and immune cell infiltration. *By inhibiting cytotoxic T-cell responses* - Some STIs might have localized immunosuppressive effects, but their primary contribution to increased HIV transmission risk is not through a generalized inhibition of **cytotoxic T-lymphocyte (CTL) responses**. - The key mechanisms are related to physical barriers and increased target cell availability, not suppression of the systemic antiviral immune response.

Q: Which of the following statements about herpes simplex virus (HSV) shedding is MOST accurate?

Asymptomatic shedding accounts for most sexual transmission. ***Asymptomatic shedding accounts for most sexual transmission*** - **Asymptomatic shedding** of HSV is very common and often goes unnoticed, leading to unsuspecting transmission to sexual partners. - Studies show that a significant proportion, often over 70%, of HSV acquisition occurs during contact with an infected partner who is **asymptomatically shedding** the virus. *HSV-1 sheds more frequently than HSV-2 in the genital tract* - While HSV-1 can cause genital herpes, **HSV-2 is the predominant cause of genital herpes** and typically sheds more frequently and for longer durations from the genital tract than HSV-1. - **Recurrent genital HSV-2 outbreaks** are also more common than recurrent genital HSV-1 outbreaks, reflecting the greater propensity for shedding. *Viral shedding occurs only during symptomatic episodes* - This statement is incorrect because **viral shedding frequently occurs in the absence of visible lesions or symptoms**, a phenomenon known as asymptomatic shedding. - Patients can shed the virus before the appearance of lesions (prodrome), during symptomatic periods, and often following resolution of symptoms or in completely **asymptomatic periods**. *Antiviral suppression completely eliminates viral shedding* - Antiviral medications like acyclovir, valacyclovir, and famciclovir can **significantly reduce the frequency and duration of HSV shedding**, both symptomatic and asymptomatic. - However, they do **not completely eliminate viral shedding**, meaning that transmission is still possible even with suppressive therapy.

Q: What is the mechanism behind the increased risk of HIV acquisition in individuals with genital herpes?

HSV disrupts epithelial barrier and recruits CD4+ cells. ***HSV disrupts epithelial barrier and recruits CD4+ cells*** - Genital herpes causes **lesions and ulcerations** in the genital mucosa, which disrupt the integrity of the epithelial barrier, creating portals of entry for HIV. - The inflammatory response to HSV infection leads to the recruitment of **CD4+ T cells** and other HIV target cells to the genital tract, making them readily available for HIV infection. *HSV glycoproteins enhance HIV binding to target cells* - While HSV modifies cellular surfaces, its glycoproteins are not directly known to **enhance HIV binding** to its primary receptors (CD4 and co-receptors) on target cells. - This mechanism is not considered a primary driver of the increased HIV acquisition risk in the context of HSV. *HSV inhibits local innate immune responses* - HSV does have mechanisms to evade host immunity, but its primary impact on HIV acquisition is not through a generalized **inhibition of overall innate immune responses** that would directly increase HIV entry. - Instead, the physical disruption and cellular recruitment are more significant factors. *HSV increases HIV viral load through transactivation* - This mechanism refers more to the potential interaction of HSV with established HIV infection to **replicate more HIV**, not primarily to the initial acquisition of HIV. - While co-infection *can* impact HIV viral replication, it's not the main reason for increased susceptibility to *acquiring* HIV.

Q: A patient is a known case of thalassemia. Which of the following viruses would be responsible for attacking progenitor cells and causing aplastic anemia?

Parvovirus B19. ***Parvovirus B19*** - **Parvovirus B19** specifically targets and replicates in **erythroid progenitor cells** in the bone marrow, leading to a temporary halt in red blood cell production [1]. - In patients with chronic hemolytic anemias like **thalassemia**, who already have increased erythropoietic demands, this can precipitate an **aplastic crisis** or pure red cell aplasia [1], [2]. *CMV (Cytomegalovirus)* - While CMV can affect the bone marrow and lead to myelosuppression, it does not typically cause a direct **aplastic crisis** by targeting erythroid progenitors in the same way as Parvovirus B19. - CMV often presents with a wider range of symptoms including fever, hepatitis, and mononucleosis-like syndrome, and bone marrow suppression is usually multi-lineage or less severe. *EBV (Epstein-Barr Virus)* - EBV is known to cause infectious mononucleosis and can also be associated with some bone marrow disorders, but it does not primarily target **erythroid progenitor cells** to cause an aplastic crisis. - Its main target cells are **B lymphocytes**, and any bone marrow suppression is often secondary to immune dysregulation rather than direct lytic infection of stem cells. *Hepatitis C virus (HCV)* - HCV infection can lead to various hematologic manifestations, including aplastic anemia, but these are typically **immune-mediated** or associated with chronic liver disease and its complications. - HCV does not directly infect and destroy **hematopoietic progenitor cells** in the bone marrow as a primary mechanism of aplastic anemia.

Question 1

Monkeypox, a viral zoonotic disease, is caused by

Accepted Answer

a double-stranded DNA virus

Answer

a single-stranded RNA virus

Answer

a single-stranded DNA virus

Answer

a double-stranded RNA virus

Question 2

Consider the following statements regarding dengue virus :

1. It has four distinct serotypes.
2. Infection with any one serotype confers lifelong immunity for that virus serotype.
3. Secondary infection with dengue serotype 2 leads to severe form of dengue. Which of the statements given above are correct?

Accepted Answer

1 and 2 only

Answer

2 and 3 only

Answer

1 and 3 only

Answer

1, 2 and 3

Question 3

Which one of the following is a characteristic of Human Immunodeficiency Virus (HIV)?

Accepted Answer

It is easily killed by heat

Answer

It is easily killed by T4 lymphocytes

Answer

It cannot cross blood brain barrier

Answer

It is resistant to acetone

Question 4

Consider the following hepatitis viruses :
1. Hepatitis A
2. Hepatitis B
3. Hepatitis C
4. Hepatitis E
Which of the above can be commonly transmitted through the faeco-oral route?

Accepted Answer

1 and 4

Answer

1 and 3 only

Answer

2, 3 and 4

Answer

1, 2 and 3

Question 5

Which is the most specific causative agent of Rabies?

Accepted Answer

Rabies lyssavirus (RABV)

Answer

Lagos bat lyssavirus (LBV)

Answer

Mokola lyssavirus (MOKV)

Answer

Duvenhage lyssavirus (DUVV)

Question 6

A patient presents with genital grouped vesicles, as shown in the image. What is the most likely causative organism?

Accepted Answer

Herpes simplex virus

Answer

Haemophilus

Answer

Klebsiella

Answer

Treponema

Question 7

How does the presence of STIs increase the risk of HIV transmission?

Accepted Answer

By disrupting mucosal barriers and causing inflammation

Answer

By direct enhancement of HIV replication

Answer

By increasing CD4 receptor density on target cells

Answer

By inhibiting cytotoxic T-cell responses

Question 8

Which of the following statements about herpes simplex virus (HSV) shedding is MOST accurate?

Accepted Answer

Asymptomatic shedding accounts for most sexual transmission

Answer

HSV-1 sheds more frequently than HSV-2 in the genital tract

Answer

Viral shedding occurs only during symptomatic episodes

Answer

Antiviral suppression completely eliminates viral shedding

Question 9

What is the mechanism behind the increased risk of HIV acquisition in individuals with genital herpes?

Accepted Answer

HSV disrupts epithelial barrier and recruits CD4+ cells

Answer

HSV glycoproteins enhance HIV binding to target cells

Answer

HSV inhibits local innate immune responses

Answer

HSV increases HIV viral load through transactivation

Question 10

A patient is a known case of thalassemia. Which of the following viruses would be responsible for attacking progenitor cells and causing aplastic anemia?

Accepted Answer

Parvovirus B19

Answer

CMV (Cytomegalovirus)

Answer

EBV (Epstein-Barr Virus)

Answer

Hepatitis C virus (HCV)

Virology — MCQs

Virology — MCQs

On this page

Practice by Chapter

Want unlimited practice?