Virology Practice Questions

Q: All are true regarding mumps, EXCEPT:

Spreads through Stensen's duct to parotid gland. ***Spreads through Stensen's duct to parotid gland*** - Mumps virus does NOT primarily enter the parotid gland via **Stensen's duct**; rather, it reaches the parotid glands via **hematogenous spread** after initial replication in the upper respiratory tract and regional lymph nodes. - Stensen's duct is the **excretory duct** for saliva drainage from the parotid gland, not a viral entry route. - This is the **false statement** in this EXCEPT question. *Incubation period is 18-21 days* - The typical incubation period for mumps is **16-18 days** (range 12-25 days), so 18-21 days falls within the acceptable range. - This relatively long incubation period allows for potential asymptomatic transmission before symptom onset. *Can cause aseptic meningitis* - Mumps is a well-known cause of **aseptic (viral) meningitis**, occurring in approximately **10-15%** of mumps cases. - CNS involvement can also include encephalitis, though this is less common. - Most cases of mumps meningitis resolve without permanent neurological sequelae. *Multiplies in respiratory epithelium* - Mumps virus is transmitted via **respiratory droplets** and initially replicates in the **nasopharyngeal mucosa and respiratory epithelial cells**. - This initial replication site leads to local viral shedding and subsequent viremia with systemic spread to glandular tissues (parotid, pancreas, testes, ovaries).

Q: Which virus is most commonly recognized as a prototypical viral hemorrhagic fever in endemic regions of West Africa?

Lassa fever virus. ***Lassa fever virus*** - Lassa fever is a prototypical **viral hemorrhagic fever (VHF)** endemic to West Africa, caused by an **Arenavirus** transmitted through contact with rodent (Mastomys) excreta. - Characterized by fever, hemorrhagic manifestations in severe cases (15-20%), and multi-organ involvement with high mortality in hospitalized patients. - Represents one of the most important VHFs due to its **endemic nature** affecting millions annually in West Africa. *Yellow fever virus* - Yellow fever causes hemorrhagic fever with prominent **jaundice** and **hepatic necrosis**, transmitted by *Aedes* mosquitoes. - A **Flavivirus** causing "yellow" fever due to liver damage, but vaccine-preventable and less commonly seen in modern practice in endemic regions. *West Nile virus* - A **Flavivirus** primarily causing **neuroinvasive disease** (meningitis, encephalitis) rather than hemorrhagic fever. - Hemorrhagic manifestations are **extremely rare** and not characteristic of West Nile virus infection. *Crimean-Congo hemorrhagic fever virus* - CCHF is a severe **tick-borne VHF** (Nairovirus) with prominent hemorrhagic features and high mortality (10-40%). - Endemic to **Africa, Asia, Eastern Europe, and Middle East** but NOT West Africa, distinguishing its geographic distribution from Lassa fever.

Q: Active replication in hepatitis B infection is indicated by:

HBeAg. ***HBeAg*** - **HBeAg (Hepatitis B e-antigen)** indicates **active viral replication** and **high infectivity** in hepatitis B infection. - Its presence signifies that the virus is actively multiplying, leading to a higher risk of transmission. *HBsAg* - **HBsAg (Hepatitis B surface antigen)** is the **first serological marker** to appear following acute infection and indicates **current infection** (either acute or chronic). - Its presence alone does not differentiate between active replication and a chronic carrier state with low viral activity. *HBcAg* - **HBcAg (Hepatitis B core antigen)** is an **intracellular antigen** found within infected hepatocytes and is typically **not detectable in serum**. - Its primary clinical utility is seen through **anti-HBc antibodies**, which indicate past or current infection. *Anti-HBsAg* - **Anti-HBsAg (Antibody to HBsAg)** indicates **immunity** to hepatitis B, either due to successful **vaccination** or **resolved infection**. - Its presence implies that the individual is no longer infected and has protective antibodies, rather than active replication.

Q: Which of the following is NOT a poxvirus?

Chickenpox. ***Chicken pox*** - **Chickenpox** is caused by the **varicella-zoster virus (VZV)**, which is a member of the **Herpesviridae** family, not the Poxviridae family. - VZV is characterized by its ability to establish **latency** in sensory ganglia, leading to potential reactivation as **shingles** later in life. *Cow pox* - **Cowpox** is a **poxvirus** that causes skin lesions in cattle and can be transmitted to humans, historically being crucial for the development of the **smallpox vaccine**. - It belongs to the **Orthopoxvirus** genus within the Poxviridae family. *Molluscum contagiosum* - **Molluscum contagiosum** is caused by the **molluscum contagiosum virus (MCV)**, which is a specific type of **poxvirus** affecting humans. - It typically causes characteristic **pearly, umbilicated papules** on the skin and is transmitted by direct contact. *Small pox* - **Smallpox** was a severe infectious disease caused by the **variola virus**, a highly virulent member of the **Orthopoxvirus** genus classified within the Poxviridae family. - It was eradicated globally through vaccination efforts, making it one of the greatest achievements in public health.

Q: Which of the following viruses specifically targets CD4+ T lymphocytes leading to progressive immunodeficiency?

HIV. ***HIV*** - **HIV** primarily targets **CD4+ T lymphocytes**, which are crucial components of the immune system found in lymphoid tissue. - The virus binds to CD4 receptors (along with co-receptors CCR5 or CXCR4) and progressively destroys these cells. - This progressive destruction leads to **immunodeficiency** and the development of AIDS. - HIV's specific tropism for CD4+ T cells distinguishes it from other viruses. *Adenovirus* - **Adenovirus** can infect various cell types, including respiratory epithelium, conjunctival cells, and gastrointestinal tract cells. - It does not have specific tropism for CD4+ T lymphocytes. - While it can cause opportunistic infections in immunocompromised individuals, it does not target T cells specifically. *Herpes virus* - **Herpes viruses** (e.g., HSV, VZV) primarily establish **latency in sensory neurons**. - EBV (a herpes virus) does target B lymphocytes, but not CD4+ T cells. - They do not cause progressive immunodeficiency through CD4+ T cell destruction. *CMV* - **CMV** (Cytomegalovirus) infects a wide range of cell types including fibroblasts, epithelial cells, endothelial cells, and monocytes. - While it can affect immunocompromised individuals, it does not specifically target CD4+ T lymphocytes. - CMV does not cause progressive immunodeficiency through selective CD4+ T cell destruction.

Q: Which is the most common causative organism involved in infections after kidney transplantation?

Cytomegalovirus. ***Cytomegalovirus*** - **Cytomegalovirus (CMV)** is the most common opportunistic infection after kidney transplantation, occurring in **50-80%** of transplant recipients. - CMV infection or reactivation typically occurs **1-6 months post-transplant** due to intense **immunosuppression** required to prevent graft rejection. - Highest risk is in **donor-positive/recipient-negative (D+/R-)** serostatus, but reactivation can occur in seropositive recipients. - CMV can cause **fever, leukopenia, graft dysfunction**, and invasive disease affecting multiple organ systems. *Klebsiella* - While *Klebsiella* can cause serious bacterial infections, particularly **urinary tract infections** and **pneumonia** in transplant patients, it is not the most common overall causative organism for post-transplant infections. - Bacterial infections like *Klebsiella* are often related to indwelling catheters or surgical sites but are less ubiquitous than viral reactivations in immunosuppressed patients. *Epstein Barr virus* - **Epstein-Barr Virus (EBV)** is another significant viral pathogen in transplant recipients, primarily associated with **post-transplant lymphoproliferative disorder (PTLD)**. - While important, EBV infection or reactivation is not as universally prevalent or as frequently symptomatic as CMV in the post-transplant period. *Herpes simplex virus* - **Herpes simplex virus (HSV)** can cause infections in transplant patients, leading to **mucocutaneous lesions** and occasionally disseminated disease. - HSV infections are generally less severe and less common than CMV, which can affect multiple organ systems and has a higher morbidity burden in this population.

Q: HIV was discovered in what year?

1983. ***1983*** - HIV (Human Immunodeficiency Virus) was definitively identified and recognized as the cause of AIDS by **Luc Montagnier** at the Institut Pasteur in Paris. - This discovery was crucial for understanding the pathogenesis of AIDS and developing diagnostic tests. *1975* - While documented cases of AIDS occurred in the 1970s, the **virus itself had not yet been identified** in 1975. - Research into rare opportunistic infections and cancers linked to immune deficiency was just beginning to gather momentum. *1995* - By 1995, significant progress had been made in understanding HIV, including the development of **highly active antiretroviral therapy (HAART)**, which revolutionized AIDS treatment. - The initial discovery of the virus happened much earlier. *1985* - In 1985, the first **HIV antibody test** was approved, allowing for widespread screening of blood products and diagnosis of infection. - This was a significant advancement, but it followed the initial discovery of the virus a few years prior.

Q: Most common organism causing laryngotracheobronchitis is:

Parainfluenzavirus. ***Parainfluenzavirus*** - **Parainfluenza viruses** (PIVs), particularly PIV-1 and PIV-2, are the **most common causes of croup** (laryngotracheobronchitis) in children. - They primarily cause inflammation and swelling of the **larynx, trachea, and bronchi**, leading to the characteristic **barking cough** and stridor. *RSV* - **Respiratory Syncytial Virus (RSV)** is the **most common cause of bronchiolitis** and pneumonia in infants and young children. - While it can cause upper respiratory symptoms, it is less frequently the primary cause of croup compared to parainfluenza viruses. *Influenza virus* - **Influenza virus** typically causes **influenza** (the flu), which presents with more systemic symptoms like high fever, body aches, and fatigue. - Although influenza can lead to severe respiratory complications, it is a less common cause of isolated laryngotracheobronchitis. *H. influenzae* - **_Haemophilus influenzae_** type b (Hib) was historically a major cause of **epiglottitis**, a severe and life-threatening infection of the epiglottis. - With widespread vaccination, Hib infections are rare, and it is not a common cause of laryngotracheobronchitis.

Q: Which one of the following is a function of the enzyme reverse transcriptase, which is unique to retroviruses?

RNA-dependent DNA polymerase activity. ***RNA-dependent DNA polymerase activity*** - **Reverse transcriptase** is a unique enzyme found in retroviruses that synthesizes **DNA from an RNA template**, hence its name "reverse" transcriptase. - This activity is crucial for the retroviral life cycle, as it allows the viral **RNA genome** to be reverse-transcribed into **DNA**, which can then integrate into the host cell's genome. *DNase activity* - **DNase** (deoxyribonuclease) enzymes degrade DNA. This activity is not a primary function of reverse transcriptase. - While integration of the viral DNA into the host genome involves DNA manipulation, the core reverse transcriptase enzyme does not exhibit DNase activity for its primary function. *RNA-dependent RNA polymerase activity* - This activity involves synthesizing **RNA from an RNA template**. It is characteristic of some **RNA viruses** (e.g., influenza virus), but not retroviruses. - Retroviruses use the host cell's machinery to transcribe their integrated DNA provirus into mRNA and new viral RNA genomes, rather than having their own RNA-dependent RNA polymerase. *RNA isomerase activity* - **RNA isomerase activity** is not a standard enzymatic function in the context of nucleic acid synthesis or modification performed by viral enzymes. - Isomerases typically rearrange atoms within a molecule. Reverse transcriptase's primary functions are polymerization and degradation of RNA/DNA hybrids, not isomerization.

Q: The virus that causes aplastic anemia in chronic hemolytic diseases is

Parvovirus. ***Parvovirus*** - **Parvovirus B19** specifically targets and destroys **erythroid progenitor cells** in the bone marrow. - In patients with chronic hemolytic diseases (e.g., **sickle cell anemia**, **spherocytosis**), where red blood cell turnover is already high, this destruction leads to a severe, acute exacerbation of anemia known as an **aplastic crisis**. *Adenovirus* - Adenoviruses typically cause a range of illnesses, including **respiratory tract infections**, gastroenteritis, and conjunctivitis. - While they can cause severe illness in immunocompromised individuals, they are **not directly implicated** in causing aplastic anemia or aplastic crisis in chronic hemolytic diseases. *Hepatitis virus* - Hepatitis viruses (A, B, C, D, E) primarily cause **inflammation of the liver**. - Although severe viral infections can rarely trigger aplastic anemia, **hepatitis viruses are not the primary or common cause** of aplastic crisis in the context of chronic hemolytic disorders. *EB virus* - **Epstein-Barr virus (EBV)** is known for causing **infectious mononucleosis** and is associated with various lymphoproliferative disorders and malignancies. - While EBV can affect the bone marrow and, in rare instances, be linked to marrow suppression, it is **not the typical or direct cause** of aplastic crisis in chronic hemolytic conditions.

Question 1

All are true regarding mumps, EXCEPT:

Accepted Answer

Spreads through Stensen's duct to parotid gland

Answer

Incubation period is 18-21 days

Answer

Multiplies in respiratory epithelium

Answer

Can cause aseptic meningitis

Question 2

Which virus is most commonly recognized as a prototypical viral hemorrhagic fever in endemic regions of West Africa?

Accepted Answer

Lassa fever virus

Answer

West Nile virus

Answer

Yellow fever virus

Answer

Crimean-Congo hemorrhagic fever virus

Question 3

Active replication in hepatitis B infection is indicated by:

Accepted Answer

HBeAg

Answer

HBsAg

Answer

HBcAg

Answer

Anti-HBsAg

Question 4

Which of the following is NOT a poxvirus?

Accepted Answer

Chickenpox

Answer

Molluscum contagiosum

Answer

Smallpox

Answer

Cowpox

Question 5

Which of the following viruses specifically targets CD4+ T lymphocytes leading to progressive immunodeficiency?

Accepted Answer

HIV

Answer

Adenovirus

Answer

Herpes virus

Answer

CMV

Question 6

Which is the most common causative organism involved in infections after kidney transplantation?

Accepted Answer

Cytomegalovirus

Answer

Klebsiella

Answer

Epstein Barr virus

Answer

Herpes simplex virus

Question 7

HIV was discovered in what year?

Accepted Answer

1983

Answer

1975

Answer

1995

Answer

1985

Question 8

Most common organism causing laryngotracheobronchitis is:

Accepted Answer

Parainfluenzavirus

Answer

RSV

Answer

Influenza virus

Answer

H. influenzae

Question 9

Which one of the following is a function of the enzyme reverse transcriptase, which is unique to retroviruses?

Accepted Answer

RNA-dependent DNA polymerase activity

Answer

DNase activity

Answer

RNA-dependent RNA polymerase activity

Answer

RNA isomerase activity

Question 10

The virus that causes aplastic anemia in chronic hemolytic diseases is

Accepted Answer

Parvovirus

Answer

Adenovirus

Answer

Hepatitis virus

Answer

EB virus

Virology — MCQs

Virology — MCQs

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