Virology Practice Questions

Q: What is the most common viral cause of acquired aqueductal stenosis?

Mumps. **Explanation:** **Correct Answer: B. Mumps** Aqueductal stenosis is a common cause of obstructive hydrocephalus. While most cases are congenital (e.g., X-linked stenosis), acquired cases are often the result of post-inflammatory scarring. **Mumps virus** is the most common viral cause of acquired aqueductal stenosis. The virus has a specific tropism for the ependymal cells lining the ventricular system. Infection leads to **ependymitis**, which results in the sloughing of ependymal cells and subsequent reactive gliosis. This inflammatory process narrows or obliterates the narrowest part of the ventricular system—the **Aqueduct of Sylvius**—leading to non-communicating hydrocephalus, often occurring weeks to months after the initial infection. **Why other options are incorrect:** * **Rubella:** While Congenital Rubella Syndrome (CRS) causes significant CNS involvement (microcephaly, mental retardation), it is more commonly associated with vascular damage and generalized encephalitis rather than isolated aqueductal stenosis. * **Toxoplasma:** *Toxoplasma gondii* is a parasite, not a virus. While it is a classic cause of obstructive hydrocephalus in neonates, it typically causes stenosis via large periventricular calcifications or inflammatory debris. * **Enterovirus:** These are common causes of viral meningitis and encephalitis (e.g., Hand-Foot-Mouth disease, Herpangina) but do not typically lead to the chronic ependymal scarring required to cause aqueductal stenosis. **High-Yield Pearls for NEET-PG:** * **Most common cause of congenital hydrocephalus:** Aqueductal stenosis. * **Most common viral cause of acquired aqueductal stenosis:** Mumps. * **Triad of Congenital Toxoplasmosis:** Hydrocephalus, Chorioretinitis, and Intracranial calcifications (diffuse). * **Mumps complications:** Orchitis (most common extra-salivary site in post-pubertal males), Oophoritis, Pancreatitis, and Aseptic meningitis.

Q: Which of the following is NOT true about Rotavirus?

Rota B can be grown in cell culture. **Explanation:** Rotavirus is the most common cause of severe diarrhea in infants and young children worldwide. Understanding its classification and cultivation is crucial for NEET-PG. **Why Option B is the Correct Answer (The False Statement):** Rotaviruses are notoriously difficult to grow in standard cell cultures. While **Group A Rotavirus** can be grown in specialized cell lines (like MA104) with the addition of proteolytic enzymes (trypsin) to enhance infectivity, **Group B and Group C Rotaviruses cannot be grown in cell culture.** Therefore, the statement that "Rota B can be grown in cell culture" is incorrect. **Analysis of Other Options:** * **Option A:** Rotaviruses are the leading cause of viral gastroenteritis in both humans and children, typically presenting with vomiting followed by watery diarrhea. * **Option C:** Rotavirus is classified into groups A through G. While Group A is the most common, **Group C** is a recognized cause of sporadic cases and outbreaks of diarrhea in children. * **Option D:** In routine clinical practice, culture is not performed because it is difficult, slow, and lacks sensitivity. Diagnosis is instead made via **ELISA** or **Latex Agglutination** for antigen detection in stool. **High-Yield Clinical Pearls for NEET-PG:** * **Morphology:** Wheel-like appearance (*Rota* = wheel) under electron microscopy due to its double-shelled capsid. * **Genome:** Segmented, double-stranded RNA (11 segments). * **Pathogenesis:** Produces an enterotoxin called **NSP4**, which induces secretory diarrhea. * **Vaccines:** Live attenuated oral vaccines (Rotarix, RotaTeq, and Rotavac) are part of the Universal Immunization Programme (UIP).

Q: Nipah virus is associated with epidemics of which condition?

Encephalitis. **Explanation:** Nipah virus (NiV) is a highly pathogenic zoonotic virus belonging to the genus **Henipavirus** (Family: Paramyxoviridae). The primary clinical manifestation of Nipah virus infection in humans is **acute encephalitis**, characterized by fever, headache, and altered consciousness, often progressing rapidly to coma and death. **Why Encephalitis is the correct answer:** The virus exhibits strong neurotropism. It enters the central nervous system via the olfactory nerve and through hematogenous spread, causing widespread vasculitis, endothelial damage, and parenchymal inflammation. This leads to severe cerebral edema and neurological deterioration, with a high case fatality rate (40% to 75%). **Analysis of other options:** * **Hepatitis:** While systemic involvement can occur, Nipah virus is not a primary hepatotropic virus. Hepatitis is not a defining clinical feature of the epidemics. * **Pneumonia:** Although Nipah virus can cause severe respiratory illness (Acute Respiratory Distress Syndrome), especially noted in the Malaysian and Singaporean outbreaks, **Encephalitis** remains the hallmark and most common cause of mortality in major epidemics (such as those in India and Bangladesh). * **All of the above:** While respiratory symptoms exist, the primary association and the "classic" board-exam presentation for Nipah is Encephalitis. **High-Yield Clinical Pearls for NEET-PG:** * **Natural Reservoir:** Fruit bats (Pteropus species). * **Transmission:** Consumption of raw date palm sap contaminated by bat saliva/urine, or direct contact with infected pigs (intermediate hosts). * **Diagnosis:** RT-PCR (gold standard) or ELISA for IgM/IgG antibodies. * **Histopathology:** Characteristic **syncytia formation** (multinucleated giant cells) in vascular endothelium. * **Recent Context:** Frequent outbreaks in Kerala, India, make this a high-priority topic.

Q: Which of the following is a member of the family Herpesviridae, characterized as an enveloped virus with an icosahedral nucleocapsid containing a double-stranded linear DNA genome?

Cytomegalovirus (CMV). **Explanation:** The question describes the classic structural characteristics of the **Herpesviridae** family. Members of this family are characterized by a **large, enveloped** virion, an **icosahedral nucleocapsid**, and a **linear double-stranded DNA (dsDNA)** genome. Between the capsid and the envelope lies a proteinaceous layer called the **tegument**. **1. Why Cytomegalovirus (CMV) is correct:** CMV (Human Herpesvirus 5) belongs to the Betaherpesvirinae subfamily. It perfectly fits the description: it is enveloped, possesses an icosahedral capsid, and contains linear dsDNA. It is a major cause of congenital infections and opportunistic infections in immunocompromised patients (e.g., transplant recipients, HIV). **2. Why the other options are incorrect:** * **Poliovirus:** A member of the *Picornaviridae* family. It is **non-enveloped** (naked) and contains a **ssRNA** genome. * **Human Papillomavirus (HPV):** A member of the *Papillomaviridae* family. While it has an icosahedral capsid and dsDNA, it is **non-enveloped** and its DNA is **circular**, not linear. * **Influenza virus:** A member of the *Orthomyxoviridae* family. It is enveloped but has a **helical** nucleocapsid and a **segmented ssRNA** genome. **Clinical Pearls for NEET-PG:** * **CMV Histology:** Look for "Owl’s eye" intranuclear inclusion bodies. * **Latency:** All Herpesviruses establish lifelong latency (CMV remains latent in mononuclear cells/lymphocytes). * **Site of Replication:** Unlike most RNA viruses, all DNA viruses (except Poxvirus) replicate in the **nucleus**. * **Envelope Origin:** Herpesviruses acquire their envelope by budding through the **inner nuclear membrane**.

Q: Which of the following conditions is NOT caused by Enterovirus (formerly Echovirus)?

Hemorrhagic conjunctivitis. **Explanation:** The question asks which condition is **NOT** caused by **Echoviruses** (a sub-genus of Enteroviruses). **1. Why "Hemorrhagic Conjunctivitis" is the correct answer:** While Echoviruses cause a wide spectrum of diseases, **Acute Hemorrhagic Conjunctivitis (AHC)** is specifically and classically caused by **Enterovirus 70** and **Coxsackievirus A24**. While these belong to the same *Enterovirus* genus, they are distinct from the Echovirus group. AHC is characterized by sudden onset of subconjunctival hemorrhage, pain, and lid edema. **2. Analysis of Incorrect Options (Conditions caused by Echoviruses):** * **Herpangina:** Primarily caused by Coxsackievirus A, but **Echoviruses** are also known causative agents. It presents with painful vesicles and ulcers on the posterior pharynx and soft palate. * **Pleurodynia (Bornholm disease):** Classically associated with Coxsackievirus B, but **Echoviruses** can also cause this paroxysmal, sharp chest pain due to intercostal muscle involvement. * **Myocarditis:** Along with Coxsackievirus B (the most common cause), **Echoviruses** are significant viral triggers for inflammatory cardiomyopathy and pericarditis. **3. NEET-PG High-Yield Pearls:** * **Echovirus** stands for *Enteric Cytopathic Human Orphan* virus. * **Aseptic Meningitis:** Echoviruses (especially types 6, 9, 11, and 30) are the **most common cause** of viral meningitis. * **Hand-Foot-Mouth Disease (HFMD):** Primarily caused by Coxsackievirus A16 and Enterovirus 71. * **Rule of Thumb:** If a question asks for the most common cause of non-polio enteroviral disease, Echoviruses are often the answer. However, for specific "hemorrhagic" eye infections, think **EV-70**.

Q: Inclusion bodies of vaccinia are known as?

Guarnieri bodies. **Explanation:** **Guarnieri bodies** are the characteristic intracytoplasmic inclusion bodies seen in cells infected with the **Vaccinia virus** (the virus used in the smallpox vaccine) and the Variola virus (Smallpox). Since Poxviruses are unique among DNA viruses because they replicate entirely within the **cytoplasm**, these inclusions represent "viral factories" where viral replication and assembly occur. They appear as eosinophilic (pinkish) masses on H&E staining. **Analysis of Incorrect Options:** * **Negri bodies:** These are pathognomonic intracytoplasmic eosinophilic inclusions found in pyramidal cells of the hippocampus and Purkinje cells of the cerebellum in **Rabies**. * **Asteroid bodies:** These are star-shaped eosinophilic inclusions found within giant cells in granulomatous conditions, most classically **Sarcoidosis** and Sporotrichosis. * **Schuffner dots:** These are fine stippling (morphological changes) seen in red blood cells infected with **Plasmodium vivax** and *Plasmodium ovale* malaria. **High-Yield Clinical Pearls for NEET-PG:** * **Poxvirus Rule:** Most DNA viruses replicate in the nucleus and produce intranuclear inclusions (e.g., Herpes - Cowdry Type A). Poxviruses are the **exception**; they replicate in the cytoplasm and produce **intracytoplasmic** inclusions (Guarnieri bodies). * **Molluscum Contagiosum:** Another Poxvirus that produces large, eosinophilic intracytoplasmic inclusions known as **Henderson-Patterson bodies**. * **Cowdry Type A:** Seen in HSV and VZV (Lipshutz bodies). * **Owl’s Eye Appearance:** Characteristic intranuclear inclusion of **CMV**.

Q: A 64-year-old man with a travel history to Southern Minnesota presents with a 2-day history of fever, headache, and vomiting. Today, he appears confused and is disoriented to simple questions. His cerebrospinal fluid analysis shows 75% neutrophils (PMNs) and is otherwise clear. A head CT scan is normal. What is the most likely cause of his symptoms?

West Nile virus. ### Explanation **Correct Answer: D. West Nile virus** The patient presents with **Encephalitis** (fever, headache, altered mental status/confusion). The key diagnostic clue is the **CSF pleocytosis with a predominance of neutrophils (PMNs)**. While most viral encephalitides present with lymphocytic pleocytosis, **West Nile Virus (WNV)** is a classic exception where an early neutrophilic shift is frequently observed. The travel history to the Midwestern United States (Minnesota) during summer/fall months is highly suggestive of WNV, which is the most common cause of epidemic viral encephalitis in the US. **Analysis of Incorrect Options:** * **A. California Encephalitis virus:** While also an arbovirus found in the Midwest, it primarily affects children (La Crosse strain) and is less common in the elderly compared to WNV. * **B. Enterovirus:** This is the most common cause of viral *meningitis*. While it can cause encephalitis, the CSF typically shows a rapid shift to lymphocytes, and the clinical severity in an elderly patient with profound confusion points more strongly toward WNV. * **C. Herpes Simplex Virus (HSV):** HSV is the most common cause of sporadic (non-epidemic) encephalitis. However, it typically presents with **temporal lobe involvement** on imaging (CT/MRI) and hemorrhagic CSF (RBCs), neither of which are present here. **NEET-PG High-Yield Pearls:** * **WNV Vector:** *Culex* mosquito; **Reservoir:** Birds (Crow/Blue Jay deaths are sentinels). * **CSF Paradox:** WNV is a "High-Yield" exception—think neutrophils in the CSF for early viral presentation. * **Clinical Sign:** Look for "West Nile Poliomyelitis" (acute flaccid paralysis) as a specific complication. * **Diagnosis:** IgM antibody capture ELISA (MAC-ELISA) in CSF is the gold standard.

Q: Creutzfeldt-Jakob disease is due to a mutation causing the misfolding of which protein?

Prion protein. **Explanation:** **Creutzfeldt-Jakob disease (CJD)** is a fatal neurodegenerative disorder caused by **Prions** (proteinaceous infectious particles). The disease arises when the normal cellular prion protein (**PrPc**), which is primarily alpha-helical, undergoes a conformational change into an abnormal, misfolded pathogenic form called **PrPsc** (rich in beta-pleated sheets). This misfolded protein is resistant to proteases, accumulates in the brain, and induces further misfolding of healthy PrPc, leading to neuronal death and the characteristic "spongiform" appearance of the brain. **Analysis of Options:** * **Option A (Beta-amyloid):** While beta-amyloid plaques are a hallmark of **Alzheimer’s disease**, they are not the primary cause of CJD. * **Option C & D (Muscle/Structural proteins):** These are general categories of proteins. CJD specifically involves the PrP protein found in the central nervous system, not systemic structural or contractile proteins. **High-Yield Clinical Pearls for NEET-PG:** * **Triad of CJD:** Rapidly progressive dementia, myoclonus (startle-induced), and characteristic periodic sharp wave complexes (PSWC) on EEG. * **Diagnosis:** The **14-3-3 protein** in CSF is a significant marker. MRI typically shows "pulvinar sign" or "hockey-stick sign" in the thalamus. * **Resistance:** Prions are highly resistant to standard sterilization (autoclaving). They require specific protocols like **1N NaOH** or **sodium hypochlorite** for 1 hour, followed by autoclaving at 134°C. * **Variant CJD (vCJD):** Associated with "Mad Cow Disease" (Bovine Spongiform Encephalopathy) and typically affects younger patients.

Q: Cell fusion of HIV with target cell is mediated by which component?

gp41. The entry of HIV into a host cell is a two-step process involving the envelope glycoprotein complex (**gp160**), which is cleaved into two subunits: **gp120** and **gp41**. ### **Why gp41 is the Correct Answer** **gp41** is the transmembrane subunit of the HIV envelope. Once gp120 binds to the CD4 receptor and a co-receptor (CCR5 or CXCR4), a conformational change occurs that exposes gp41. gp41 then acts as a "fusion peptide," inserting itself into the host cell membrane and pulling the viral and cellular membranes together. This **cell-to-cell fusion** allows the viral capsid to enter the cytoplasm. ### **Analysis of Incorrect Options** * **gp120 (Option A):** This is the surface subunit responsible for **attachment/docking**. It binds to the CD4 receptor. While essential for the process, it does not mediate the actual fusion of membranes. * **p24 (Option B):** This is the **capsid protein**. It forms the inner conical core of the virus. It is a major diagnostic marker (p24 antigenemia) but is not involved in membrane fusion. * **p18 (Option D):** This is the **matrix protein** (also known as p17) that lies just beneath the viral envelope, providing structural integrity. ### **High-Yield Clinical Pearls for NEET-PG** * **Enfuvirtide:** A fusion inhibitor drug that works by binding to gp41, preventing the conformational change required for viral entry. * **Maraviroc:** A drug that binds to the **CCR5 co-receptor** on the host cell, preventing gp120 binding. * **Mnemonic:** gp**120** is for **Attachment** (120 is "outside"), gp**41** is for **Fusion** (41 "penetrates" the membrane). * **Screening vs. Confirmatory:** p24 is the earliest marker detected in blood (Screening/Early diagnosis); Western Blot (detecting gp120, gp41, p24) was traditionally the confirmatory test.

Question 1

Which of the following is true regarding the hepatitis E virus?

Accepted Answer

It is associated with increased mortality in pregnant females.

Answer

It is seen in post-transfusion cases.

Answer

It is associated with the hepatitis B virus.

Answer

All of the above.

Question 2

What is the most common viral cause of acquired aqueductal stenosis?

Accepted Answer

Mumps

Answer

Rubella

Answer

Toxoplasma

Answer

Enterovirus

Question 3

Which of the following is NOT true about Rotavirus?

Accepted Answer

Rota B can be grown in cell culture

Answer

Causes diarrhea in man and children

Answer

Rota C can cause diarrhea in children

Answer

Culture cannot be done

Question 4

Nipah virus is associated with epidemics of which condition?

Accepted Answer

Encephalitis

Answer

Hepatitis

Answer

Pneumonia

Answer

All of the above

Question 5

Which of the following is a member of the family Herpesviridae, characterized as an enveloped virus with an icosahedral nucleocapsid containing a double-stranded linear DNA genome?

Accepted Answer

Cytomegalovirus (CMV)

Answer

Poliovirus

Answer

Human Papillomavirus (HPV)

Answer

Influenza virus

Question 6

Which of the following conditions is NOT caused by Enterovirus (formerly Echovirus)?

Accepted Answer

Hemorrhagic conjunctivitis

Answer

Herpangina

Answer

Pleurodynia

Answer

Myocarditis

Question 7

Inclusion bodies of vaccinia are known as?

Accepted Answer

Guarnieri bodies

Answer

Negri bodies

Answer

Asteroid bodies

Answer

Schuffner dots

Question 8

A 64-year-old man with a travel history to Southern Minnesota presents with a 2-day history of fever, headache, and vomiting. Today, he appears confused and is disoriented to simple questions. His cerebrospinal fluid analysis shows 75% neutrophils (PMNs) and is otherwise clear. A head CT scan is normal. What is the most likely cause of his symptoms?

Accepted Answer

West Nile virus

Answer

California Encephalitis virus

Answer

Enterovirus

Answer

Herpes Simplex Virus (HSV)

Question 9

Creutzfeldt-Jakob disease is due to a mutation causing the misfolding of which protein?

Accepted Answer

Prion protein

Answer

Beta-amyloid protein

Answer

Muscle proteins

Answer

Structural proteins

Question 10

Cell fusion of HIV with target cell is mediated by which component?

Accepted Answer

gp41

Answer

gp 120

Answer

p24

Answer

p 18

Virology — MCQs

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