Virology Practice Questions

Q: A 5-year-old boy presents with headache, fever, and vomiting. On examination, multiple small vesicles are present on the posterior pharyngeal wall. He is diagnosed with herpangina. What is herpangina caused by?

Enterovirus. **Explanation:** **Correct Answer: B. Enterovirus** Herpangina is a common childhood infection primarily caused by **Coxsackievirus Group A** (a genus within the **Enterovirus** family, Picornaviridae). The clinical hallmark is the sudden onset of fever, sore throat, and the appearance of small (1–2 mm) vesicular or ulcerative lesions specifically on the **posterior pharyngeal wall**, tonsils, and soft palate. Unlike gingivostomatitis (HSV-1), herpangina typically spares the buccal mucosa and gingiva. **Analysis of Incorrect Options:** * **A. Myxovirus:** This group includes Orthomyxoviruses (Influenza) and Paramyxoviruses (Measles, Mumps). These typically present with respiratory symptoms or parotitis, not posterior pharyngeal vesicles. * **C. Rhabdovirus:** The most notable member is the Rabies virus, which causes fatal encephalitis and hydrophobia, not localized vesicular pharyngitis. * **D. Rhinovirus:** While also a Picornavirus, Rhinoviruses are the primary cause of the common cold (upper respiratory tract infections) and do not typically cause vesicular eruptions. **High-Yield Clinical Pearls for NEET-PG:** * **Causative Agent:** Most commonly **Coxsackie A** (A1–A10, A16, A22). * **Hand-Foot-Mouth Disease (HFMD):** Also caused by Enteroviruses (Coxsackie A16 and Enterovirus 71). It differs from herpangina by the presence of a maculopapular or vesicular rash on the palms, soles, and buttocks. * **Seasonality:** Infections peak during summer and autumn months. * **Transmission:** Fecal-oral route and respiratory droplets. * **Management:** Treatment is purely supportive (hydration and analgesics) as the condition is self-limiting.

Q: Which of the following statements regarding Hepatitis E Virus (HEV) and Hepatitis D Virus (HDV) is FALSE?

HEV and HDV are DNA viruses.. ### Explanation **1. Why Option D is the Correct (False) Statement:** The fundamental classification of Hepatitis viruses is a high-yield NEET-PG topic. **Hepatitis E Virus (HEV)** and **Hepatitis D Virus (HDV)** are both **RNA viruses**. Specifically, HEV is a non-enveloped, single-stranded RNA virus (Hepeviridae), and HDV is a defective, single-stranded circular RNA virus (Deltavirus). In the mnemonic "Vowels are Bowels" (A and E), both are RNA viruses transmitted via the feco-oral route. Only Hepatitis B (HBV) is a DNA virus. **2. Analysis of Other Options:** * **Option A:** It is clinically possible for a patient to have multiple viral infections simultaneously, especially in high-risk groups (e.g., IV drug users or endemic areas), though they have different transmission routes (HEV is feco-oral; HDV is parenteral). * **Option B:** HDV infection occurs in two patterns: **Co-infection** (simultaneous with HBV) and **Superinfection** (HDV infecting a chronic HBV carrier). Superinfection is significantly more serious, often leading to rapid progression to cirrhosis or fulminant hepatic failure. * **Option C:** HDV is a **defective virus**. It requires the Hepatitis B Surface Antigen (HBsAg) to provide its outer envelope for assembly and transmission. Without an underlying HBV infection, HDV cannot propagate. **3. High-Yield Clinical Pearls for NEET-PG:** * **HEV & Pregnancy:** HEV carries a high mortality rate (up to 20%) in pregnant women, particularly in the third trimester, due to fulminant hepatic failure. * **HEV Genotypes:** Genotypes 1 and 2 are human-only (epidemic); Genotypes 3 and 4 are zoonotic (pork/deer meat). * **HDV Diagnosis:** The presence of **Anti-HDV IgM** indicates acute infection, while **HDV RNA** is the gold standard for active replication. * **Prevention:** The HBV vaccine indirectly prevents HDV infection because HDV cannot exist without HBV.

Q: In which cells does the Human Immunodeficiency Virus primarily replicate?

CD4 helper T cells. **Explanation:** The Human Immunodeficiency Virus (HIV) is a retrovirus that exhibits specific tropism for cells expressing the **CD4 molecule** on their surface. **1. Why CD4 helper T cells are correct:** The primary mechanism of HIV entry involves the binding of the viral envelope glycoprotein **gp120** to the **CD4 receptor** on the host cell. This interaction, along with co-receptors (**CCR5** on macrophages/early infection or **CXCR4** on T cells/late infection), triggers a conformational change in **gp41**, leading to membrane fusion and viral entry. CD4+ T helper cells are the principal targets because they express high densities of these receptors, making them the primary site for viral replication and subsequent depletion, which leads to AIDS. **2. Why the other options are incorrect:** * **CD8 T cells:** These are cytotoxic T cells that lack the CD4 receptor. While they play a role in the immune response *against* HIV, the virus cannot infect them directly. * **Natural Killer (NK) cells:** These are part of the innate immune system. Like CD8 cells, they do not express the CD4 receptor required for HIV entry. **High-Yield Clinical Pearls for NEET-PG:** * **Coreceptors:** **CCR5** is used by M-tropic strains (early stage); **CXCR4** is used by T-tropic strains (late stage). A mutation in the CCR5 gene (**CCR5-Δ32**) provides resistance to HIV infection. * **Other Target Cells:** Besides T cells, HIV infects **Macrophages, Dendritic cells, and Microglial cells** (the primary reservoir in the CNS), as these also express CD4. * **Markers:** The progression to AIDS is clinically defined when the CD4+ T cell count falls below **200 cells/mm³**.

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.

Question 1

A 5-year-old boy presents with headache, fever, and vomiting. On examination, multiple small vesicles are present on the posterior pharyngeal wall. He is diagnosed with herpangina. What is herpangina caused by?

Accepted Answer

Enterovirus

Answer

Myxovirus

Answer

Rhabdovirus

Answer

Rhinovirus

Question 2

Which of the following statements regarding Hepatitis E Virus (HEV) and Hepatitis D Virus (HDV) is FALSE?

Accepted Answer

HEV and HDV are DNA viruses.

Answer

Both HEV and HDV can infect simultaneously.

Answer

HDV causes a more serious infection due to superinfection.

Answer

HDV cannot infect in the absence of HBV.

Question 3

In which cells does the Human Immunodeficiency Virus primarily replicate?

Accepted Answer

CD4 helper T cells

Answer

CD8 T cells

Answer

Natural killer cells

Answer

None of the above

Question 4

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 5

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 6

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 7

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 8

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 9

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 10

Which of the following is/are arboviral diseases?

Accepted Answer

Hand-foot-mouth disease

Answer

Japanese encephalitis

Answer

Dengue

Answer

Kyasanur Forest Disease (KFD)

Virology — MCQs

Virology — MCQs

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