Virology Practice Questions

Q: An immunologist is working on growing influenza virus for vaccine production. Which of the following sites is used for the production of vaccine in a fertilized egg?

Allantoic cavity. **Explanation:** The cultivation of viruses in embryonated eggs is a classic virological technique. For **Influenza virus**, the site of inoculation depends on the purpose of the study. **1. Why Allantoic Cavity is Correct:** The **allantoic cavity** is the preferred site for the **mass production of vaccines**. It provides a large volume of allantoic fluid, allowing the virus to replicate to high titers. This makes it commercially viable for harvesting large quantities of viral antigen required for inactivated or live-attenuated influenza vaccines. **2. Analysis of Incorrect Options:** * **Amniotic Cavity:** This site is primarily used for the **primary isolation** of the Influenza virus from clinical samples (e.g., throat swabs). Once isolated, the virus is usually adapted to the allantoic cavity for further growth. * **Chorioallantoic Membrane (CAM):** This site is used for viruses that produce visible **pocks** (lesions), such as Variola (Smallpox), Vaccinia, and Herpes Simplex Virus (HSV). * **Yolk Sac:** This is the site of choice for cultivating **Chlamydia**, Rickettsiae, and some viruses like the St. Louis encephalitis virus. **Clinical Pearls & High-Yield Facts for NEET-PG:** * **Influenza Vaccine:** Most seasonal flu vaccines are still produced in eggs; hence, a history of **egg allergy** is a traditional contraindication (though modern guidelines allow for supervised administration in some cases). * **Age of Embryo:** For allantoic/amniotic inoculation, 10–12 day old embryos are used; for yolk sac, 5–8 day old embryos are used. * **Detection:** Viral growth in the allantoic fluid is typically detected via the **Hemagglutination (HA) test**.

Q: A patient is seen 1 month post-renal transplant with fever. Which of the following is the most likely organism responsible?

Hepatitis C virus. In post-renal transplant patients, the timing of infection is the most critical diagnostic clue. Infections are generally categorized into three phases: **1. The Correct Answer: Hepatitis C Virus (HCV)** The first month post-transplant (Early Phase) is dominated by infections present in the recipient prior to transplant or those transmitted via the donor organ. **Hepatitis C** and Hepatitis B are frequently pre-existing or donor-derived. During this period, the high dose of induction immunosuppression can lead to the reactivation or exacerbation of these viral loads. **2. Analysis of Incorrect Options:** * **Polyoma virus (BK virus):** Typically causes BK virus-associated nephropathy (BKVAN) much later, usually **3 to 6 months** post-transplant, as it requires sustained immunosuppression to reactivate in the graft. * **HHV-6:** While it can occur early, it most commonly manifests between **2 to 6 weeks** (peaking at 1 month) but is statistically less common as a primary cause of fever compared to pre-existing viral states or surgical complications in the first month. * **Varicella Zoster Virus (VZV):** Reactivation (Shingles) or primary infection typically occurs in the late phase, usually **after 6 months**, when maintenance immunosuppression is ongoing. **Clinical Pearls for NEET-PG:** * ** 6 Months:** Community-acquired infections and late viral reactivations (VZV, BK virus). * **High-Yield:** CMV is the most common viral pathogen overall, but it rarely presents in the first 2 weeks; it typically peaks at 1–3 months.

Q: Hepatitis B virus in infected people can be detected in all of the following bodily fluids, EXCEPT:

Stool. **Explanation:** The Hepatitis B Virus (HBV) is a blood-borne pathogen primarily transmitted through parenteral, sexual, and perinatal routes. The presence of the virus in bodily fluids depends on the degree of viremia and the permeability of mucosal barriers. **Why Stool is the Correct Answer:** Unlike Hepatitis A and Hepatitis E, which are transmitted via the **fecal-oral route** and excreted in feces, Hepatitis B is **not found in stool**. The virus is highly sensitive to the bile salts and proteolytic enzymes present in the gastrointestinal tract, which degrade the viral envelope, rendering it non-infectious and undetectable in feces. **Analysis of Incorrect Options:** * **Blood:** This is the primary vehicle for HBV. It contains the highest concentration of infectious virions (Dane particles) and viral antigens (HBsAg). * **Semen & Vaginal Secretions:** HBV is present in significant concentrations in genital fluids, making sexual contact a major route of transmission. * **Saliva:** While the concentration is lower than in blood, HBV DNA and HBsAg are detectable in saliva. Although inefficient, transmission via human bites or shared items contaminated with saliva is biologically possible. **NEET-PG High-Yield Pearls:** * **Concentration Gradient:** HBV concentration is **High** in blood/serum; **Moderate** in semen, vaginal fluid, and saliva; and **Insignificant/Absent** in stool, urine, sweat, and tears. * **Infectivity:** HBV is 50–100 times more infectious than HIV and can survive on environmental surfaces for at least 7 days. * **Marker of Infectivity:** The presence of **HBeAg** in any of these fluids correlates with high viral replication and maximum infectivity.

Q: A 15-year-old girl presents with symptoms suggestive of rabies. What is the characteristic shape of the rabies virus?

Bullet shape. **Explanation:** The correct answer is **C. Bullet shape**. The Rabies virus belongs to the **Rhabdoviridae** family (genus *Lyssavirus*). Under electron microscopy, it exhibits a highly characteristic **bullet-shaped** morphology. This shape is formed by a cylindrical nucleocapsid surrounded by a lipid envelope containing glycoprotein spikes. One end of the virion is typically rounded (hemispherical), while the other is flat or concave. **Analysis of Incorrect Options:** * **A. Brick shape:** This is characteristic of the **Poxviridae** family (e.g., Variola and Molluscum contagiosum). These are the largest and most complex viruses. * **B. Icosahedral shape:** This is the most common viral symmetry, seen in many DNA viruses (like Herpesvirus and Adenovirus) and some RNA viruses (like Poliovirus). * **D. Rod shape:** This is typical of certain plant viruses (e.g., Tobacco Mosaic Virus) or filamentous viruses like **Ebola** (Filoviridae), which are long and thread-like rather than bullet-shaped. **High-Yield Clinical Pearls for NEET-PG:** * **Negri Bodies:** These are pathognomonic intracytoplasmic, eosinophilic inclusion bodies found most commonly in the **Purkinje cells of the cerebellum** and pyramidal cells of the **hippocampus**. * **Genome:** It is a negative-sense, single-stranded RNA virus. * **Pathogenesis:** The virus travels via **retrograde axonal transport** through peripheral nerves to the CNS. * **Prophylaxis:** Post-exposure prophylaxis (PEP) includes wound cleaning, Rabies Immunoglobulin (RIG), and the modern cell-culture vaccine (given on days 0, 3, 7, 14, and 28).

Q: Lymphoid tissue is the site of latent infection for which of the following herpes viruses?

Epstein barr virus. **Explanation:** The hallmark of the **Herpesviridae** family is the ability to establish lifelong **latent infections**, where the virus remains dormant in specific host cells and can reactivate later. **Why Epstein-Barr Virus (EBV) is correct:** EBV (Human Herpesvirus 4) primarily infects **B-lymphocytes** and epithelial cells. After the initial infection (often presenting as Infectious Mononucleosis), the virus establishes latency in the **memory B-cells** located within **lymphoid tissues** (tonsils, spleen, and lymph nodes). It utilizes the host's B-cell proliferation machinery to maintain its genome without killing the cell. **Analysis of Incorrect Options:** * **Herpes Simplex Virus Type 1 (HSV-1):** Establishes latency in the **sensory nerve ganglia**, most commonly the **Trigeminal ganglion**. It typically causes orolabial lesions. * **Herpes Simplex Virus Type 2 (HSV-2):** Establishes latency in the **sacral ganglia**. It is primarily associated with genital herpes. * **Cytomegalovirus (CMV):** Establishes latency in **monocytes, macrophages, and CD34+ myeloid progenitor cells** (bone marrow), rather than lymphoid tissue specifically. **High-Yield NEET-PG Pearls:** * **Alpha-herpesvirinae (HSV-1, 2, VZV):** Latency in **Neurons**. * **Beta-herpesvirinae (CMV, HHV-6, 7):** Latency in **Mononuclear cells/Glands**. * **Gamma-herpesvirinae (EBV, KSHV/HHV-8):** Latency in **Lymphoid tissue (B-cells)**. * **EBV Association:** It is linked to several malignancies, including Burkitt Lymphoma, Nasopharyngeal Carcinoma, and Hodgkin Lymphoma. * **Diagnostic Test:** The **Paul-Bunnell Test** (Heterophile antibody test) is the classic screening tool for EBV-induced Infectious Mononucleosis.

Q: Which virus is the most common cause of acute hemorrhagic conjunctivitis?

Coxsackievirus A24. **Explanation:** **Acute Hemorrhagic Conjunctivitis (AHC)** is a highly contagious ocular infection characterized by sudden onset of painful, red eyes, subconjunctival hemorrhage, and lid edema. **Why Coxsackievirus A24 is correct:** The two primary etiologic agents of AHC are **Enterovirus 70 (EV70)** and **Coxsackievirus A24 variant (CVA24v)**. Both belong to the *Picornaviridae* family. While EV70 was historically the first identified cause of pandemics, **Coxsackievirus A24** is currently recognized as the most frequent cause of large-scale outbreaks and sporadic cases worldwide. These viruses are transmitted via the feco-oral route or direct contact with eye secretions. **Analysis of Incorrect Options:** * **B. Newcastle disease virus:** This is primarily a pathogen of poultry. It can cause mild, self-limiting conjunctivitis in humans (usually laboratory workers or poultry handlers), but it is not a common cause of AHC. * **C. Measles virus:** Measles typically presents with a non-purulent catarrhal conjunctivitis as part of its prodromal phase (along with cough and coryza), but it does not cause the characteristic hemorrhagic presentation. * **D. Mumps virus:** Mumps is primarily associated with parotitis and orchitis; ocular involvement is rare and usually manifests as dacryoadenitis or episcleritis, not hemorrhagic conjunctivitis. **High-Yield Clinical Pearls for NEET-PG:** * **Incubation Period:** Very short (24–48 hours). * **Key Feature:** "Apollo Conjunctivitis" is a synonym for AHC (named after the 1969 Apollo 11 mission during which an outbreak occurred). * **Neurological Complication:** Enterovirus 70 is specifically associated with a rare, polio-like **radiculomyelitis** (cranial nerve palsies or paralysis). * **Adenovirus:** While Adenovirus (Serotypes 8, 19, 37) causes **Epidemic Keratoconjunctivitis (EKC)**, it is less commonly associated with the rapid, widespread subconjunctival hemorrhage seen in AHC.

Q: Which of the following is/are arboviral diseases?

Hand-foot-mouth disease. **Explanation:** The term **Arbovirus** (Arthropod-borne virus) refers to a functional group of viruses that are transmitted to humans through the bite of infected arthropods, primarily mosquitoes and ticks. **Why Hand-foot-mouth disease (HFMD) is the correct answer (as the non-arboviral disease):** HFMD is caused by viruses belonging to the **Picornaviridae** family, most commonly **Coxsackievirus A16** and **Enterovirus 71**. Unlike arboviruses, these are transmitted via the **fecal-oral route**, respiratory droplets, or direct contact with lesion fluid. They do not require an arthropod vector for transmission. **Analysis of Incorrect Options (Arboviral Diseases):** * **Japanese Encephalitis (JE):** An arboviral disease caused by a Flavivirus. It is transmitted by the **Culex tritaeniorhynchus** mosquito. * **Dengue:** Caused by the Dengue virus (Flavivirus) and transmitted primarily by the **Aedes aegypti** mosquito. * **Kyasanur Forest Disease (KFD):** A viral hemorrhagic fever caused by a Flavivirus. It is a tick-borne disease transmitted by **Haemaphysalis spinigera**. **High-Yield Clinical Pearls for NEET-PG:** * **Arbovirus Families:** Most belong to *Flaviviridae* (Dengue, JE, KFD, West Nile, Zika), *Togaviridae* (Chikungunya), or *Bunyaviridae* (Crimean-Congo Hemorrhagic Fever). * **Vector Identification:** Always remember the specific vectors: *Aedes* (Dengue/Zika/Chikungunya), *Culex* (JE), and *Ticks* (KFD/CCHF). * **HFMD Presentation:** Characterized by a vesicular rash on the palms, soles, and oral ulcers (herpangina). It is a common pediatric infection and is **not** seasonal in the same way vector-borne diseases are.

Q: Which of the following is NOT included in the picornavirus group?

Hepatitis E virus (HEV). **Explanation:** The **Picornaviridae** family consists of small (pico), non-enveloped, positive-sense single-stranded RNA viruses. **Why Hepatitis E Virus (HEV) is the correct answer:** Hepatitis E virus was previously classified under Picornaviridae due to its similar morphology. However, it is now classified in its own family, **Hepeviridae** (Genus: *Orthohepevirus*). Unlike picornaviruses, HEV has a unique genomic organization and is the only major hepatitis virus that is "quasi-enveloped" in the blood but non-enveloped in feces. **Analysis of Incorrect Options:** * **Poliovirus:** A classic member of the *Enterovirus* genus within the Picornaviridae family. It is the causative agent of paralytic poliomyelitis. * **Foot and Mouth Disease Virus (FMDV):** Belonging to the *Aphthovirus* genus, it is a highly infectious picornavirus affecting cloven-hoofed animals; it is historically significant as the first animal virus discovered. * **Encephalomyocarditis Virus (EMCV):** A member of the *Cardiovirus* genus within Picornaviridae, known for causing encephalitis and myocarditis in a wide range of mammalian hosts. **High-Yield Clinical Pearls for NEET-PG:** * **Picornavirus Mnemonic (PERCH):** **P**olio, **E**cho, **R**hino, **C**oxsackie, and **H**epatitis A. * **Hepatitis E Key Fact:** It is the most common cause of acute viral hepatitis worldwide and carries a high mortality rate (up to 20%) in **pregnant women** due to fulminant hepatic failure. * **Rhinovirus:** The only picornavirus that is **acid-labile** (destroyed by stomach acid), which is why it causes respiratory infections rather than GI disease.

Q: What is the first virological marker following acute Hepatitis B infection?

HBsAg. **Explanation:** **Hepatitis B Surface Antigen (HBsAg)** is the correct answer because it is the **first detectable virological marker** in the serum following an acute infection. It typically appears 2 to 8 weeks before the onset of clinical symptoms (jaundice) and biochemical evidence of liver damage (elevated ALT). Its presence indicates that the individual is infectious. **Analysis of Incorrect Options:** * **IgM Anti-HBc (Option A):** This is the first **antibody** to appear. It is crucial for diagnosing acute infection during the "window period" (when HBsAg has disappeared but Anti-HBs hasn't appeared yet). However, it appears after HBsAg. * **Anti-HBs (Option C):** This antibody appears during the recovery phase after HBsAg disappears. It signifies immunity (either from past infection or vaccination). * **Anti-HBe (Option D):** This antibody appears after the disappearance of HBeAg. It indicates a transition from high infectivity to a low-replicative state. **High-Yield Clinical Pearls for NEET-PG:** * **First marker to appear:** HBsAg. * **First antibody to appear:** IgM Anti-HBc. * **Marker of Infectivity:** HBeAg (indicates active viral replication). * **Window Period Marker:** IgM Anti-HBc is the only positive marker. * **Marker of Vaccination:** Only Anti-HBs is positive (HBsAg and Anti-HBc will be negative). * **Chronic Infection:** Defined by the persistence of HBsAg for >6 months.

Q: Malaise and fatigue with increased "atypical" lymphocytes and a reactive heterophil antibody test is most commonly caused by?

Epstein-Barr virus. **Explanation:** The clinical presentation of malaise, fatigue, and fever, combined with the presence of **atypical lymphocytes** (Downey cells) and a **positive heterophil antibody test** (Monospot test), is the classic triad for **Infectious Mononucleosis (IM)**, most commonly caused by the **Epstein-Barr Virus (EBV)**. 1. **Why EBV is correct:** EBV infects B-lymphocytes via the CD21 receptor. In response, the body produces cytotoxic T-cells (CD8+) to control the infection; these activated T-cells appear as "atypical lymphocytes" on a peripheral smear. The virus also induces polyclonal B-cell activation, leading to the production of **heterophil antibodies** (antibodies that agglutinate sheep or horse RBCs), which is the diagnostic hallmark of EBV-induced IM. 2. **Why other options are incorrect:** * **Toxoplasma:** Can cause a mononucleosis-like syndrome but is **heterophil-negative**. * **Borrelia burgdorferi:** The causative agent of Lyme disease, typically presenting with erythema migrans (bull’s eye rash), arthritis, or neurological symptoms, not heterophil-positive IM. * **Parvovirus (B19):** Causes Erythema Infectiosum (Fifth disease) characterized by a "slapped-cheek" rash or aplastic crisis in patients with hemolytic anemia. **High-Yield NEET-PG Pearls:** * **Paul-Bunnell Test:** The specific heterophil antibody test used for EBV diagnosis. * **CMV:** The most common cause of **heterophil-negative** mononucleosis. * **Ampicillin Rash:** Patients with EBV-IM who are mistakenly treated with Ampicillin or Amoxicillin often develop a characteristic maculopapular rash. * **Atypical Lymphocytes:** These are NOT infected B-cells; they are **reactive T-cells** (CD8+).

Question 1

An immunologist is working on growing influenza virus for vaccine production. Which of the following sites is used for the production of vaccine in a fertilized egg?

Accepted Answer

Allantoic cavity

Answer

Chorioallantoic membrane

Answer

Yolk sac

Answer

Amniotic cavity

Question 2

A patient is seen 1 month post-renal transplant with fever. Which of the following is the most likely organism responsible?

Accepted Answer

Hepatitis C virus

Answer

Polyoma virus/BK virus

Answer

Varicella virus

Answer

HHV-6

Question 3

Hepatitis B virus in infected people can be detected in all of the following bodily fluids, EXCEPT:

Accepted Answer

Stool

Answer

Semen

Answer

Saliva

Answer

Blood

Question 4

A 15-year-old girl presents with symptoms suggestive of rabies. What is the characteristic shape of the rabies virus?

Accepted Answer

Bullet shape

Answer

Brick shape

Answer

Icosahedral shape

Answer

Rod shape

Question 5

Lymphoid tissue is the site of latent infection for which of the following herpes viruses?

Accepted Answer

Epstein barr virus

Answer

Cytomegalovirus

Answer

Herpes simplex virus type 1

Answer

Herpes simplex virus type 2

Question 6

Which virus is the most common cause of acute hemorrhagic conjunctivitis?

Accepted Answer

Coxsackievirus A24

Answer

Newcastle disease virus

Answer

Measles virus

Answer

Mumps virus

Question 7

Which of the following is/are arboviral diseases?

Accepted Answer

Hand-foot-mouth disease

Answer

Japanese encephalitis

Answer

Dengue

Answer

Kyasanur Forest Disease (KFD)

Question 8

Which of the following is NOT included in the picornavirus group?

Accepted Answer

Hepatitis E virus (HEV)

Answer

Encephalomyocarditis virus

Answer

Foot and mouth disease virus

Answer

Poliovirus

Question 9

What is the first virological marker following acute Hepatitis B infection?

Accepted Answer

HBsAg

Answer

IgM Anti-HBc

Answer

Anti-HBs

Answer

Anti-HBe

Question 10

Malaise and fatigue with increased "atypical" lymphocytes and a reactive heterophil antibody test is most commonly caused by?

Accepted Answer

Epstein-Barr virus

Answer

Toxoplasma

Answer

Borrelia burgdorferi

Answer

Parvovirus

Virology — MCQs

Virology — MCQs

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