Virology — MCQs

Virology Indian Medical PG Practice Questions and MCQs

Question 11: Lipschutz inclusion bodies are seen in infections caused by which virus?

A. Herpes virus (Correct Answer)
B. Vaccinia virus
C. Hepatitis-A virus
D. Hanta virus

Explanation: **Explanation:** **Lipschütz inclusion bodies** are characteristic **intranuclear, eosinophilic (acidophilic) Type A inclusion bodies** found in cells infected with the **Herpes Simplex Virus (HSV)**. 1. **Why Herpes virus is correct:** In Herpes infections, viral replication occurs within the host cell nucleus. This process leads to the formation of Cowdry Type A inclusions (specifically named Lipschütz bodies in the context of HSV). These appear as dense, granular masses surrounded by a clear "halo" (the halo effect is due to the peripheral displacement of host chromatin against the nuclear membrane). 2. **Why other options are incorrect:** * **Vaccinia virus:** This is a Poxvirus. Unlike Herpes, Poxviruses replicate in the cytoplasm, producing **Guarnieri bodies** (intracytoplasmic eosinophilic inclusions). * **Hepatitis A virus:** This virus typically does not produce pathognomonic inclusion bodies visible on routine light microscopy; diagnosis relies on serology (IgM anti-HAV). * **Hanta virus:** This is a Bunyavirus that replicates in the cytoplasm. While it may cause cellular changes, it is not associated with Lipschütz bodies. **High-Yield Clinical Pearls for NEET-PG:** * **Cowdry Type A (Granular/Dense):** Seen in Herpes Simplex, Varicella-Zoster, and Yellow Fever (Torres bodies). * **Cowdry Type B (Circumscribed/Multiple):** Seen in Adenovirus and Poliovirus. * **Tzanck Smear:** A rapid bedside test for Herpes that shows **multinucleated giant cells** and Lipschütz bodies. * **Negri Bodies:** Intracytoplasmic inclusions pathognomonic for **Rabies** (found in Hippocampus/Purkinje cells). * **Owl’s Eye Appearance:** Characteristic intranuclear inclusions seen in **Cytomegalovirus (CMV)**.

Question 12: A patient presents with fever, cough, and headache. A rash appears on the third day of illness. What is the probable diagnosis?

A. Measles (Correct Answer)
B. Mumps
C. Smallpox
D. Chickenpox

Explanation: **Explanation:** The clinical presentation of fever, cough, and headache followed by the appearance of a rash on the **third day** of illness is a classic description of **Measles (Rubeola)**. **1. Why Measles is correct:** Measles typically follows a predictable timeline: a prodromal phase (Days 1–3) characterized by the "3 Cs" (Cough, Coryza, and Conjunctivitis) and high fever. The maculopapular rash typically appears on the **3rd to 4th day**, starting behind the ears and spreading cephalocaudally (head to toe). The presence of Koplik spots (pathognomonic) usually precedes the rash. **2. Why other options are incorrect:** * **Mumps:** Primarily presents with parotitis (swelling of salivary glands). While it involves fever and headache, a generalized maculopapular rash is not a standard clinical feature. * **Smallpox:** The rash typically appears on the **3rd or 4th day**, but it is characterized by deep-seated, firm, centrifugal vesicles/pustules that are all at the same stage of development, unlike the morbilliform rash of measles. * **Chickenpox:** The rash appears very early, usually on the **1st day** of fever. It is pleomorphic (lesions in different stages: papules, vesicles, crusts) and has a centripetal distribution (starts on the trunk). **High-Yield Clinical Pearls for NEET-PG:** * **Koplik Spots:** Small white spots on buccal mucosa opposite the lower 2nd molars (appears 2 days before the rash). * **Vitamin A:** Supplementation reduces morbidity and mortality in measles. * **SSPE (Subacute Sclerosing Panencephalitis):** A rare, late neurological complication occurring years after infection. * **Infectivity:** Most infectious during the prodromal stage (4 days before to 4 days after the rash appears).

Question 13: What are the important coreceptors for HIV to bind with CD4 receptors?

A. CCR4 and CXCR3
B. CCR5 and CXCR4 (Correct Answer)
C. CCR4 and CXCR5
D. CCR4 and CXCR2

Explanation: **Explanation:** The entry of HIV-1 into host cells is a multi-step process. The viral envelope glycoprotein **gp120** first binds to the **CD4 receptor** on T-lymphocytes or macrophages. However, this binding is insufficient for viral entry; a conformational change must occur to allow gp120 to bind to a **coreceptor**. 1. **CCR5 (Chemokine receptor type 5):** Primarily found on macrophages and dendritic cells. Strains that use this coreceptor are termed **M-tropic (R5 strains)** and are typically responsible for the **initial infection** and horizontal transmission. 2. **CXCR4 (CXC chemokine receptor type 4):** Primarily found on T-lymphocytes. Strains using this are termed **T-mropic (X4 strains)** and usually appear in the **later stages** of HIV infection, correlating with rapid CD4 decline and progression to AIDS. **Analysis of Incorrect Options:** * **Options A, C, and D:** While CCR4, CXCR2, CXCR3, and CXCR5 are legitimate chemokine receptors involved in leukocyte trafficking and immune responses, they do not serve as the primary coreceptors for HIV entry. **High-Yield Clinical Pearls for NEET-PG:** * **Maraviroc:** A CCR5 antagonist (entry inhibitor) used in treatment; it is ineffective against X4-tropic virus. * **CCR5-Δ32 Mutation:** A 32-base pair deletion in the CCR5 gene. Homozygous individuals are **resistant** to HIV infection, while heterozygotes show delayed progression to AIDS. * **gp41:** Once coreceptor binding occurs, the transmembrane protein gp41 undergoes a conformational change to mediate **fusion** of the viral envelope with the host cell membrane (inhibited by **Enfuvirtide**).

Question 14: The virus causing which of the following diseases produces both intranuclear and intracytoplasmic inclusion bodies?

A. Chickenpox
B. Rabies
C. Smallpox
D. Measles (Correct Answer)

Explanation: ### Explanation The correct answer is **Measles (Rubeola)**. #### 1. Why Measles is Correct Measles virus, a member of the *Paramyxoviridae* family, is unique because it replicates in the cytoplasm but produces viral proteins that aggregate in both the nucleus and the cytoplasm. These are known as **Warthin-Finkeldey giant cells** (multinucleated giant cells) which contain: * **Intranuclear inclusions:** Cowdry type A inclusions. * **Intracytoplasmic inclusions:** Aggregates of viral nucleocapsids. #### 2. Analysis of Incorrect Options * **Chickenpox (Varicella-Zoster Virus):** As a Herpesvirus, it replicates in the nucleus. It produces **only intranuclear** inclusion bodies (Cowdry type A), also known as Lipschütz bodies. * **Rabies (Lyssavirus):** This RNA virus replicates entirely in the cytoplasm. It produces pathognomonic **only intracytoplasmic** inclusion bodies called **Negri bodies**, most commonly found in Purkinje cells of the cerebellum and pyramidal cells of the hippocampus. * **Smallpox (Variola Virus):** Although a DNA virus, Poxviruses replicate in the cytoplasm. They produce **only intracytoplasmic** inclusion bodies known as **Guarnieri bodies**. #### 3. NEET-PG High-Yield Pearls * **Both Intranuclear & Intracytoplasmic:** Measles and Cytomegalovirus (CMV). *Note: CMV is famous for the "Owl’s eye" appearance, which is a large intranuclear inclusion.* * **Only Intranuclear:** All Herpesviruses (HSV, VZV, CMV), Adenovirus, and Papovavirus. * **Only Intracytoplasmic:** Poxvirus (Guarnieri bodies), Rabies (Negri bodies), Molluscum contagiosum (Henderson-Patterson bodies), and Trachoma (Halberstaedter-Prowazek bodies). * **Measles Clinical Triad:** Cough, Coryza, and Conjunctivitis + Koplik spots (pathognomonic).

Question 15: Influenza is caused by which virus?

A. Paramyxovirus
B. Orthomyxovirus (Correct Answer)
C. Bunyaviridae
D. Togaviridae

Explanation: **Explanation:** **Correct Answer: B. Orthomyxovirus** Influenza viruses (Types A, B, and C) belong to the **Orthomyxoviridae** family. These are pleomorphic, enveloped viruses characterized by a **segmented, single-stranded, negative-sense RNA genome**. The segmentation (8 segments in Influenza A and B) is the critical genetic feature that allows for **Antigenic Shift** (genetic reassortment), leading to pandemics. The virus attaches to host cells via Hemagglutinin (HA) and is released via Neuraminidase (NA) spikes. **Why other options are incorrect:** * **Paramyxovirus:** This family includes viruses like Mumps, Measles, and Parainfluenza. Unlike Orthomyxoviruses, their genome is **non-segmented**, meaning they do not undergo antigenic shift. * **Bunyaviridae:** This family includes Hantavirus and Crimean-Congo hemorrhagic fever virus. While they have segmented genomes, they are typically arthropod-borne (except Hantavirus) and have 3 segments, not 8. * **Togaviridae:** These are positive-sense, single-stranded RNA viruses. Key members include Rubella and Alpha viruses (e.g., Chikungunya). **High-Yield Clinical Pearls for NEET-PG:** * **Antigenic Drift:** Minor point mutations in HA/NA causing seasonal epidemics (seen in Influenza A & B). * **Antigenic Shift:** Major genetic reassortment causing pandemics (seen **only** in Influenza A). * **Drug of Choice:** Oseltamivir (Neuraminidase inhibitor) is the preferred treatment. * **Culture:** The **allantoic cavity** of embryonated specific pathogen-free (SPF) eggs is the gold standard for isolation. * **Strains:** Influenza A is the most virulent and the only one associated with zoonotic shifts (e.g., H1N1, H5N1).

Question 16: Negri bodies are characteristic of which disease?

A. Measles
B. Tetanus
C. HIV/AIDS
D. Rabies (Correct Answer)

Explanation: **Explanation:** **Negri bodies** are the pathognomonic histopathological hallmark of **Rabies**. These are eosinophilic, sharply outlined, round or oval **intracytoplasmic inclusion bodies** found in the cytoplasm of neurons. They represent sites of viral replication and are most commonly found in the **Pyramidal cells of the Hippocampus** and the **Purkinje cells of the Cerebellum**. **Analysis of Options:** * **Rabies (Correct):** Caused by the Lyssavirus (Rhabdoviridae family). Negri bodies are diagnostic, though their absence does not rule out the disease. * **Measles:** Characterized by **Warthin-Finkeldey cells** (multinucleated giant cells) and Cowdry type A inclusion bodies (both intranuclear and intracytoplasmic). * **Tetanus:** Caused by *Clostridium tetani* toxin. It is a clinical diagnosis; it does not produce inclusion bodies as it is a bacterial disease affecting neurotransmitter release. * **HIV/AIDS:** A retroviral infection. While it can cause various CNS pathologies (like PML or Toxoplasmosis), Negri bodies are not associated with it. **High-Yield Clinical Pearls for NEET-PG:** * **Shape:** Rabies virus is **bullet-shaped**. * **Receptor:** It binds to **Nicotinic Acetylcholine receptors** (nAchR) at the neuromuscular junction. * **Migration:** The virus travels via **retrograde axonal transport** to the CNS. * **Other Inclusions:** * **Guarnieri bodies:** Smallpox * **Henderson-Patterson bodies:** Molluscum contagiosum * **Cowdry Type A:** Herpes Simplex, Varicella Zoster * **Owl’s Eye appearance:** Cytomegalovirus (CMV)

Question 17: Which cells does HIV primarily infect?

A. CD4+ cells (Correct Answer)
B. CD8+ cells
C. NK cells
D. All of these

Explanation: **Explanation:** The Human Immunodeficiency Virus (HIV) is a retrovirus that exhibits specific tropism for cells expressing the **CD4 molecule** on their surface. The primary mechanism of entry involves the viral envelope glycoprotein **gp120** binding to the CD4 receptor. This interaction, along with co-receptors (CCR5 or CXCR4), allows the virus to fuse with the host cell membrane. * **CD4+ cells (Correct):** These are the primary targets. While **Helper T-lymphocytes** are the most well-known targets, HIV also infects other CD4-expressing cells, including **monocytes, macrophages, and dendritic cells** (which act as viral reservoirs). * **CD8+ cells (Incorrect):** These are Cytotoxic T-cells. They do not express the CD4 receptor required for gp120 binding. In fact, CD8+ cell counts often initially rise as the body attempts to fight the infection, though the CD4:CD8 ratio eventually reverses (<1). * **NK cells (Incorrect):** Natural Killer cells are part of the innate immune system and do not typically express the CD4 receptors necessary for primary HIV infection. **High-Yield Clinical Pearls for NEET-PG:** 1. **Co-receptors:** **CCR5** is required for initial infection (M-tropic strains); a homozygous **CCR5-Δ32 mutation** provides resistance to HIV infection. **CXCR4** is associated with late-stage disease (T-mropic strains). 2. **Markers:** The depletion of CD4+ T-cells is the hallmark of AIDS progression. A count **<200 cells/mm³** defines the transition to AIDS. 3. **Viral Entry:** Remember the sequence: **gp120** for attachment (to CD4) and **gp41** for fusion/penetration. 4. **Reservoirs:** Macrophages and Microglial cells (in the CNS) serve as important long-term reservoirs where the virus persists despite HAART.

Question 18: In a person with HIV-1 infection, which of the following is the most predictive of the patient's prognosis?

A. CD4+ cell count
B. CD4:CD8 cell ratio
C. Level of HIV-1 RNA in plasma (Correct Answer)
D. Degree of lymphadenopathy

Explanation: ### Explanation The correct answer is **Level of HIV-1 RNA in plasma (Viral Load)**. **1. Why Viral Load is the Best Predictor of Prognosis:** In HIV-1 infection, the plasma viral load (measured by RT-PCR) reflects the **rate of viral replication**. It is the single best predictor of the **speed of disease progression** and the risk of death. A high set-point of HIV RNA early in the infection correlates strongly with a faster decline in CD4+ cells and a quicker progression to AIDS. While CD4+ counts tell us the current state of the immune system, the viral load tells us how fast that system is being destroyed. **2. Why Other Options are Incorrect:** * **CD4+ Cell Count:** This is the best indicator of the **current immune status** and the immediate risk of opportunistic infections. It is used to stage the disease and decide when to start prophylaxis (e.g., for PCP), but it is less predictive of long-term prognosis than viral load. * **CD4:CD8 Ratio:** While this ratio typically reverses in HIV (becoming <1.0), it is a non-specific marker of immune activation and is not as clinically reliable for prognosis as the absolute viral load. * **Degree of Lymphadenopathy:** Persistent Generalized Lymphadenopathy (PGL) is common in the clinical latency stage but does not correlate accurately with viral replication rates or long-term survival. **3. High-Yield Clinical Pearls for NEET-PG:** * **Gold Standard for Monitoring ART:** Plasma HIV RNA levels (Viral load) are used to monitor the effectiveness of Antiretroviral Therapy. The goal is "undetectable" levels (<20–50 copies/mL). * **Window Period Marker:** **p24 antigen** is the earliest protein marker detectable (part of 4th gen ELISA). * **Diagnosis in Infants:** HIV DNA PCR is the investigation of choice for infants born to HIV-positive mothers (ELISA is avoided due to maternal IgG). * **Mnemonic:** **V**iral Load = **V**elocity of progression; **C**D4 Count = **C**urrent status.

Question 19: Which of the following is considered a newly emerged infectious agent?

A. Nipah virus (Correct Answer)
B. Pneumocystis jirovecii
C. Coronavirus
D. SARS

Explanation: **Explanation:** The concept of **Emerging Infectious Diseases (EIDs)** refers to infections that have newly appeared in a population or have existed but are rapidly increasing in incidence or geographic range. **Why Nipah Virus is Correct:** Nipah virus (NiV) is a classic example of a **newly emerged zoonotic virus**. It was first identified in **1998-1999** during an outbreak among pig farmers in Malaysia. It is a highly fatal Henipavirus (Paramyxoviridae family) transmitted by *Pteropus* bats (fruit bats). In the context of recent Indian outbreaks (notably in Kerala), it is categorized as a significant emerging public health threat. **Analysis of Incorrect Options:** * **Pneumocystis jirovecii (B):** This is a well-known opportunistic fungus. While it gained prominence during the 1980s HIV/AIDS epidemic, it is considered a "re-emerging" or established pathogen rather than a "newly emerged" agent in the current chronological context. * **Coronavirus (C):** This is a broad family of viruses (including those causing the common cold) that have been known for decades. The family itself is not "newly emerged." * **SARS (D):** While SARS-CoV was an emerging virus in 2003, it has been effectively eradicated from human circulation since 2004. In competitive exams, when compared to Nipah (which continues to cause periodic new outbreaks), Nipah is the preferred answer for "newly emerged." **High-Yield Clinical Pearls for NEET-PG:** * **Reservoir:** Fruit bats (*Pteropus* species). * **Transmission:** Direct contact with infected pigs, contaminated date palm sap, or human-to-human via respiratory droplets. * **Clinical Presentation:** Severe encephalitis (high mortality rate ~40-75%) and atypical pneumonia. * **Diagnosis:** RT-PCR (Gold standard) and ELISA for IgM/IgG. * **Other Emerging Viruses to remember:** Zika, Ebola, MERS-CoV, and Crimean-Congo Hemorrhagic Fever (CCHF).

Question 20: Which of the following mosquitoes is involved in the spread of Japanese encephalitis?

A. Aedes
B. Anopheles
C. Culex (Correct Answer)
D. Mansonoides

Explanation: **Explanation:** Japanese Encephalitis (JE) is caused by a **Flavivirus** and is the most common cause of epidemic viral encephalitis in India. **Why Culex is correct:** The primary vector for JE is the **Culex mosquito**, specifically the ***Culex tritaeniorhynchus*** group. These mosquitoes are "instar" breeders, typically found in stagnant water like **paddy fields**. They are zoophilic (prefer animal blood) and exophagic (bite outdoors), usually during dusk and night. In the JE transmission cycle, **pigs** act as the "amplifier hosts," while water birds (herons, egrets) are the natural reservoirs. Humans are "dead-end hosts" because the viremia in humans is insufficient to infect a biting mosquito. **Why other options are incorrect:** * **Aedes:** Primarily transmits Dengue, Chikungunya, Zika, and Yellow Fever. It is a day-biter and breeds in artificial containers. * **Anopheles:** The principal vector for Malaria. * **Mansonoides:** Known for transmitting Brugian Filariasis (Malayan filariasis). **High-Yield Clinical Pearls for NEET-PG:** * **Vaccine:** The live-attenuated **SA-14-14-2** strain is used in the Universal Immunization Programme (UIP) in India. * **Diagnosis:** **MAC-ELISA** (detection of IgM antibodies in CSF or serum) is the gold standard. * **MRI Finding:** Characteristically shows bilateral **thalamic involvement** (hyperintensities). * **Seasonality:** Cases typically peak during the post-monsoon season, coinciding with rice cultivation.

Practice by Chapter

Virus Structure and Classification

Practice Questions

Viral Replication

Practice Questions

Pathogenesis of Viral Infections

Practice Questions

DNA Viruses: Herpesviruses

Practice Questions

DNA Viruses: Poxviruses and Adenoviruses

Practice Questions

Hepatitis Viruses

Practice Questions

RNA Viruses: Orthomyxoviruses

Practice Questions

RNA Viruses: Paramyxoviruses

Practice Questions

Enteroviruses and Rhinoviruses

Practice Questions

Arboviruses

Practice Questions

HIV and Retroviruses

Practice Questions

Oncogenic Viruses

Practice Questions

Want unlimited practice?

Get full access to all questions, explanations, and performance tracking.

Start For Free

Virology — MCQs

Virology — MCQs

On this page

Practice by Chapter

Want unlimited practice?