Virology Practice Questions

Q: Which of the following statements about the influenza A virus is true?

Hemagglutinin and neuraminidase are strain-specific.. **Explanation:** **1. Why Option D is Correct:** The influenza A virus is classified into subtypes based on its surface glycoproteins: **Hemagglutinin (H)** and **Neuraminidase (N)**. These proteins are highly variable and undergo frequent mutations. Because they are the primary targets of the host immune response, the specific combination and structure of H and N define the particular **strain** (e.g., H1N1, H3N2). Antibodies against these surface antigens provide immunity only to that specific strain. **2. Why the Other Options are Incorrect:** * **Option A:** Influenza A belongs to the *Orthomyxoviridae* family. It has a **single-stranded**, negative-sense, segmented RNA genome (8 segments), not double-stranded. * **Option B:** Pandemics are caused by **Antigenic Shift**, which involves a major genetic reassortment leading to a completely new subtype. **Antigenic Drift** (point mutations) causes seasonal epidemics. * **Option C:** The **Nucleocapsid (NP)** and Matrix (M1) proteins are the internal type-specific antigens used to differentiate Influenza A, B, and C. They are **relatively stable** and do not vary between strains of the same type; therefore, NP antibodies are type-specific but **not strain-specific**. **High-Yield Clinical Pearls for NEET-PG:** * **Antigenic Shift:** Seen only in Influenza A (due to its wide animal reservoir). * **Hemagglutinin (H):** Responsible for cell attachment (via sialic acid receptors) and agglutination of RBCs. * **Neuraminidase (N):** Facilitates the release of progeny virions from infected cells; inhibited by **Oseltamivir**. * **Amantadine/Rimantadine:** Act by inhibiting the **M2 ion channel** (only effective against Influenza A).

Q: Which of the following viruses is labile to acid but heat stable?

Rhinovirus. **Explanation:** The correct answer is **Rhinovirus**. This question tests the fundamental differentiation between genera within the *Picornaviridae* family based on physical properties. **1. Why Rhinovirus is correct:** Rhinoviruses are the primary cause of the common cold. A defining characteristic of Rhinoviruses is their **acid lability** (they are inactivated at a pH < 5.0–6.0). This property prevents them from surviving the acidic environment of the stomach, which is why they primarily infect the upper respiratory tract rather than the gastrointestinal tract. Conversely, they are relatively **heat stable**, surviving for long periods on environmental surfaces at room temperature, which facilitates transmission via fomites. **2. Why the other options are incorrect:** * **Options A, B, and C (Enteroviruses):** Human enterovirus 70, 68, and Echoviruses all belong to the genus *Enterovirus*. Unlike Rhinoviruses, Enteroviruses are **acid-stable** (resistant to pH 3.0). This allows them to pass through the stomach unharmed and colonize the intestine. While they are also relatively stable at room temperature, the distinguishing factor in this question is their resistance to acid. **High-Yield Clinical Pearls for NEET-PG:** * **Temperature Preference:** Rhinoviruses grow best at **33°C** (the temperature of the nasal mucosa) rather than 37°C (body temperature). * **Receptor:** Most Rhinoviruses (90%) use **ICAM-1** (CD54) as their cellular receptor. * **Transmission:** Hand-to-eye or hand-to-nose contact via contaminated surfaces is more common than aerosol transmission. * **Vaccination:** No vaccine is available due to the existence of over 100 distinct serotypes.

Q: Which disease is characterized by the presence of Torres bodies in the liver cells in its early stage?

Yellow fever. **Explanation:** The correct answer is **Yellow Fever**. **Yellow Fever** is a viral hemorrhagic fever caused by a Flavivirus. The virus is hepatotropic, leading to significant liver pathology. **Torres bodies** are characteristic acidophilic (eosinophilic) intranuclear inclusion bodies found in hepatocytes during the early stages of the disease. As the disease progresses, these are often accompanied by **Councilman bodies**, which represent apoptotic, eosinophilic degeneration of hepatocytes. **Analysis of Incorrect Options:** * **Kala-azar (Visceral Leishmaniasis):** Caused by *Leishmania donovani*, it is characterized by the presence of **LD bodies** (Leishman-Donovan bodies), which are amastigote forms found within macrophages, not Torres bodies. * **Q Fever:** Caused by *Coxiella burnetii*, the classic liver finding is a **"doughnut granuloma"** (a fibrin-ring granuloma), not intranuclear inclusions. * **Lymphogranuloma venereum (LGV):** Caused by *Chlamydia trachomatis* (serotypes L1-L3), it is characterized by **Gamna-Favre bodies** (large intracytoplasmic inclusions) within lymph nodes, typically presenting as the "Groove sign." **High-Yield Clinical Pearls for NEET-PG:** * **Vector:** *Aedes aegypti* mosquito is the primary vector. * **Councilman Bodies:** Though seen in Yellow Fever, they are not pathognomonic as they can also appear in viral hepatitis. * **Vaccine:** The **17D vaccine** is a live-attenuated vaccine providing immunity for life (International Certificate of Vaccination is valid starting 10 days after vaccination). * **Faget’s Sign:** A clinical hallmark of Yellow Fever where there is **relative bradycardia** despite a high fever.

Q: A 4-year-old child presented with fatigue, malaise, fever, sore throat, headache, nausea, abdominal pain, and myalgia. On examination, generalized lymphadenopathy and hepatosplenomegaly were noted. There was marked tonsillar enlargement along with palatal petechiae, rashes, and edema of the eyelids. A peripheral smear was performed, and the Paul Bunnel test was positive. All of the following can be caused by the organism responsible for these symptoms, except one?

Primary effusion lymphoma. ### Explanation **Diagnosis:** The clinical presentation of fever, sore throat, generalized lymphadenopathy, hepatosplenomegaly, and palatal petechiae, combined with a positive **Paul Bunnel test** and atypical lymphocytosis on peripheral smear, confirms a diagnosis of **Infectious Mononucleosis** caused by the **Epstein-Barr Virus (EBV)**. **Why Option D is Correct:** **Primary Effusion Lymphoma (PEL)** is a rare B-cell lymphoma primarily associated with **Human Herpesvirus 8 (HHV-8)**, also known as Kaposi Sarcoma-associated Herpesvirus (KSHV). While EBV can be a co-infector in PEL, HHV-8 is the definitive causative agent. **Why Other Options are Incorrect:** EBV is a potent oncogenic virus associated with several malignancies due to its ability to immortalize B-cells and epithelial cells: * **A. Nasopharyngeal Carcinoma:** Strongly associated with EBV, particularly the undifferentiated type (Type 3), common in Southern China and parts of Africa. * **B. Non-Hodgkin Lymphoma (NHL):** EBV is linked to several NHL subtypes, most notably **Burkitt Lymphoma** (endemic form), Hodgkin Lymphoma (mixed cellularity), and B-cell lymphomas in immunocompromised patients. * **C. Diffuse Gastric Carcinoma:** Approximately 10% of gastric adenocarcinomas worldwide are associated with EBV. **Clinical Pearls for NEET-PG:** * **Classic Triad of IM:** Fever, Pharyngitis, and Lymphadenopathy (usually posterior cervical). * **The "Ampicillin Rash":** If a patient with IM is mistakenly treated with Ampicillin or Amoxicillin, a characteristic maculopapular rash often develops. * **Hematology:** Look for **Downey cells** (atypical T-lymphocytes) on peripheral smear. * **Hoagland Sign:** Early transient upper eyelid edema seen in Infectious Mononucleosis. * **Splenic Rupture:** A rare but life-threatening complication; patients are advised to avoid contact sports for 3–4 weeks.

Q: Which of the following viruses is not a common cause of viral encephalitis?

Herpes simplex virus type 2. The correct answer is **Herpes simplex virus type 2 (HSV-2)**. ### **Explanation** The distinction between HSV-1 and HSV-2 is a high-yield concept in neuro-virology. * **HSV-1** is the most common cause of sporadic, fatal **viral encephalitis** in adults, typically involving the temporal lobes. * **HSV-2**, conversely, is primarily associated with **aseptic meningitis** in adults (Mollaret’s meningitis) and disseminated encephalitis only in **neonates** (acquired during birth). In the context of general viral encephalitis among the adult/pediatric population, HSV-2 is not considered a "common" cause. ### **Analysis of Incorrect Options** * **Japanese Encephalitis Virus (JEV):** This is the most common cause of epidemic viral encephalitis in India. It specifically targets the basal ganglia and thalamus. * **Nipah Virus:** An emerging zoonotic paramyxovirus (reservoir: fruit bats) known for causing outbreaks of severe encephalitis with high mortality rates, particularly in Kerala, India. * **Cytomegalovirus (CMV):** A significant cause of viral encephalitis in immunocompromised individuals (e.g., HIV/AIDS patients), often presenting as ventriculoencephalitis. ### **NEET-PG High-Yield Pearls** 1. **Site Specificity:** HSV-1 encephalitis classically shows a predilection for the **temporal lobes** (look for hemorrhagic necrosis on MRI). 2. **Diagnosis:** **CSF PCR** is the gold standard for diagnosing HSV encephalitis. 3. **Treatment:** Intravenous **Acyclovir** is the drug of choice and should be started empirically if encephalitis is suspected. 4. **India Context:** Always remember JEV for "epidemic" scenarios and Nipah for "outbreak" scenarios in South India.

Q: All of the following are viral inclusion bodies except?

Psammoma bodies. **Explanation:** The correct answer is **Psammoma bodies** because they are not viral inclusion bodies; rather, they are characteristic **extracellular collections of calcium** (dystrophic calcification). Microscopically, they appear as laminated, concentric whorled structures. They are high-yield markers for specific tumors, most notably **Papillary carcinoma of the thyroid**, **Serous cystadenocarcinoma of the ovary**, and **Meningioma**. **Analysis of Viral Inclusion Bodies (Incorrect Options):** Viral inclusion bodies are nuclear or cytoplasmic aggregates of stainable substances (usually viral proteins or nucleic acids) formed during viral replication. * **Guarneri bodies:** These are eosinophilic, **intracytoplasmic** inclusion bodies found in cells infected with **Variola virus (Smallpox)** or Vaccinia virus. * **Bollinger bodies:** These are large, granular, eosinophilic **intracytoplasmic** inclusions seen in **Fowlpox**. * **Paschen bodies:** These represent the actual **virus particles (virions)** of Variola/Vaccinia when seen under a light microscope using special stains (like Gutstein’s stain). They are considered the smallest visible particles in smallpox. **NEET-PG High-Yield Pearls:** * **Negri bodies:** Intracytoplasmic inclusions in pyramidal cells of the hippocampus/Purkinje cells (Pathognomonic for **Rabies**). * **Owl’s eye appearance:** Large intranuclear inclusions seen in **CMV** (Cytomegalovirus). * **Cowdry Type A:** Intranuclear inclusions seen in **Herpes Simplex Virus (HSV)** and Yellow Fever (Torres bodies). * **Molluscum bodies (Henderson-Patterson bodies):** Large, eosinophilic cytoplasmic inclusions seen in **Molluscum contagiosum**.

Q: A 40-year-old HIV-seropositive male presents with multiple, multicentric skin lesions and lymphadenitis. What is the most likely cause of this condition?

Human Herpesvirus 8 (HHV-8). **Explanation:** The clinical presentation of multicentric skin lesions and lymphadenitis in an HIV-positive patient is highly suggestive of **Kaposi Sarcoma (KS)**. Kaposi Sarcoma is an angioproliferative disorder caused by **Human Herpesvirus 8 (HHV-8)**, also known as Kaposi Sarcoma-associated Herpesvirus (KSHV). **Why HHV-8 is correct:** In immunocompromised individuals (especially those with low CD4 counts), HHV-8 infects vascular and lymphatic endothelial cells. This leads to the formation of characteristic violaceous (purple) macules, plaques, or nodules. The "Epidemic" or AIDS-associated form is often aggressive, presenting with widespread cutaneous involvement, lymph node enlargement, and potential visceral involvement (GI tract or lungs). **Why other options are incorrect:** * **HHV-3 (Varicella-Zoster Virus):** Causes Chickenpox and Herpes Zoster (Shingles). While common in HIV patients, it presents as painful, dermatomal vesicular rashes, not multicentric vascular nodules. * **HHV-6:** Causes Roseola Infantum (Exanthem Subitum) in children. In adults/HIV patients, it may cause pneumonitis or encephalitis but is not associated with multicentric skin tumors. * **HHV-5 (Cytomegalovirus):** A common opportunistic infection in AIDS (retinitis, colitis). While it can cause skin ulcers, it does not cause the multicentric proliferative lesions seen in KS. **High-Yield Clinical Pearls for NEET-PG:** * **Histopathology:** Look for "Spindle cells," "Slit-like vascular spaces," and "Promontory sign." * **HHV-8 Associations:** Besides KS, it is linked to **Primary Effusion Lymphoma** and **Multicentric Castleman Disease**. * **Treatment:** Highly Active Antiretroviral Therapy (HAART) is the first line; systemic chemotherapy (e.g., Liposomal Doxorubicin) is used for advanced disease.

Q: All of the following are examples of intracytoplasmic inclusion bodies except?

Owl's eye bodies. **Explanation:** In virology, inclusion bodies are distinct structures formed in the nucleus or cytoplasm of host cells during viral replication. They serve as "viral factories" or sites of capsid assembly. **Why Option D is correct:** **Owl’s eye bodies** are the characteristic **intranuclear** inclusion bodies seen in **Cytomegalovirus (CMV)** infections. They are large, eosinophilic inclusions surrounded by a clear halo, extending to the nuclear membrane. Because they are located within the nucleus, they are not intracytoplasmic. (Note: "Owl's eye" appearance is also used to describe Reed-Sternberg cells in Hodgkin Lymphoma, but in virology, it specifically refers to CMV). **Why the other options are incorrect:** * **A. Molluscum bodies (Henderson-Patterson bodies):** Large, eosinophilic **intracytoplasmic** inclusions found in the epidermis in *Molluscum contagiosum* (Poxvirus). * **B. Guarneri bodies:** Eosinophilic **intracytoplasmic** inclusions diagnostic of **Variola (Smallpox)** or Vaccinia virus. * **C. Bollinger bodies:** Large **intracytoplasmic** inclusions seen in **Fowlpox**. These contain smaller internal structures known as Borrel bodies. **High-Yield Clinical Pearls for NEET-PG:** * **Poxviruses** are the only DNA viruses that replicate in the cytoplasm; hence, they produce **intracytoplasmic** inclusions. * **Negri bodies** (intracytoplasmic) are pathognomonic for **Rabies** (found in Hippocampus/Purkinje cells). * **Cowdry Type A** (intranuclear) are seen in **Herpes Simplex Virus (HSV)** and Varicella-Zoster Virus (VZV). * **Torres bodies** (intranuclear) are seen in **Yellow Fever**. * **Measles** is unique as it can produce **both** intranuclear and intracytoplasmic inclusions (Warthin-Finkeldey cells).

Q: HIV binds to macrophages having which of the following molecules?

CD4 and CCR5 molecule. **Explanation:** The entry of HIV into host cells is a multi-step process requiring both a primary receptor and a co-receptor. 1. **Why Option C is correct:** HIV primarily infects cells expressing the **CD4 molecule** (the primary receptor). However, binding to CD4 alone is insufficient for viral entry. The virus must also bind to a chemokine co-receptor. **Macrophages** (and memory T-cells) predominantly express the **CCR5** co-receptor. Strains of HIV that utilize CCR5 are termed **M-tropic (Macrophage-tropic)** or R5 strains. These are typically responsible for the initial infection and horizontal transmission. 2. **Why other options are incorrect:** * **Option A:** While CD4 is necessary, it is not the only molecule required; a co-receptor is mandatory for membrane fusion. * **Option B:** **CXCR4** is the co-receptor found primarily on **naive T-helper cells**. Strains using CXCR4 are termed **T-tropic** or X4 strains and usually appear in the later stages of HIV infection, associated with a rapid decline in CD4 counts. * **Option D:** These are both co-receptors; without the primary **CD4** docking site, the virus cannot initiate the attachment process. **High-Yield Clinical Pearls for NEET-PG:** * **gp120:** The viral envelope protein that binds to the CD4 receptor. * **gp41:** The viral protein responsible for fusion with the host cell membrane. * **Maraviroc:** A CCR5 antagonist (entry inhibitor) used in HIV treatment; it is only effective against R5-tropic virus. * **CCR5-Δ32 Mutation:** A genetic mutation (32-base pair deletion) that provides homozygous individuals with significant resistance to HIV infection.

Question 1

Which of the following statements about the influenza A virus is true?

Accepted Answer

Hemagglutinin and neuraminidase are strain-specific.

Answer

It has a double-stranded segmented RNA genome.

Answer

Pandemics are caused by antigenic drift.

Answer

Nucleocapsid antibody is not strain-specific.

Question 2

Which of the following viruses is labile to acid but heat stable?

Accepted Answer

Rhinovirus

Answer

Human enterovirus serotype 70

Answer

Human enterovirus serotype 68

Answer

Echovirus

Question 3

Which disease is characterized by the presence of Torres bodies in the liver cells in its early stage?

Accepted Answer

Yellow fever

Answer

Kala-azar

Answer

Q fever

Answer

Lymphogranuloma venereum (LGV)

Question 4

A 4-year-old child presented with fatigue, malaise, fever, sore throat, headache, nausea, abdominal pain, and myalgia. On examination, generalized lymphadenopathy and hepatosplenomegaly were noted. There was marked tonsillar enlargement along with palatal petechiae, rashes, and edema of the eyelids. A peripheral smear was performed, and the Paul Bunnel test was positive. All of the following can be caused by the organism responsible for these symptoms, except one?

Accepted Answer

Primary effusion lymphoma

Answer

Nasopharyngeal carcinoma

Answer

Non-Hodgkin lymphoma

Answer

Diffuse gastric carcinoma

Question 5

Which of the following viruses is not a common cause of viral encephalitis?

Accepted Answer

Herpes simplex virus type 2

Answer

Japanese encephalitis virus

Answer

Nipah virus

Answer

Cytomegalovirus

Question 6

All of the following are viral inclusion bodies except?

Accepted Answer

Psammoma bodies

Answer

Guarneri bodies

Answer

Bollinger bodies

Answer

Paschen bodies

Question 7

A 40-year-old HIV-seropositive male presents with multiple, multicentric skin lesions and lymphadenitis. What is the most likely cause of this condition?

Accepted Answer

Human Herpesvirus 8 (HHV-8)

Answer

Human Herpesvirus 3 (HHV-3)

Answer

Human Herpesvirus 6 (HHV-6)

Answer

Human Herpesvirus 5 (HHV-5)

Question 8

Over a holiday weekend, more than 100 adults at a resort hotel develop a diarrheal illness marked by voluminous, watery stools more than 10 times per day. They also report headaches, abdominal cramping pain, and myalgias. On physical examination, they have manifestations of dehydration and mild fever. Laboratory studies of stool samples show no increase in leukocytes or fat and no RBCs. Their illness lasts just 1 to 3 days and resolves with no sequelae. Which of the following infectious agents is the most likely cause of their illness?

Accepted Answer

Norovirus

Answer

Cytomegalovirus

Answer

Clostridium botulinum

Answer

Staphylococcus aureus

Question 9

All of the following are examples of intracytoplasmic inclusion bodies except?

Accepted Answer

Owl's eye bodies

Answer

Molluscum bodies

Answer

Guarneri bodies

Answer

Bollinger bodies

Question 10

HIV binds to macrophages having which of the following molecules?

Accepted Answer

CD4 and CCR5 molecule

Answer

CD4 molecule

Answer

CD4 and CXCR molecules

Answer

CXCR and CCR5 molecules

Virology — MCQs

Virology — MCQs

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