Virology — MCQs

Virology Indian Medical PG Practice Questions and MCQs

Question 551: Which of the following is NOT true about Nipah virus?

A. It is a paramyxovirus.
B. It causes hemorrhagic fever. (Correct Answer)
C. It is an emerging infection.
D. It is present in India.

Explanation: ### Explanation **Nipah Virus (NiV)** is a highly pathogenic zoonotic virus that primarily causes **severe encephalitis** and respiratory illness, rather than hemorrhagic fever. **1. Why Option B is the Correct Answer (The "NOT True" statement):** Nipah virus is characterized by its neurotropism. The clinical hallmark is **acute encephalitis** (fever, headache, altered consciousness, and seizures) and severe respiratory distress (ARDS). Unlike viruses like Ebola, Marburg, or Dengue, Nipah does **not** typically cause a viral hemorrhagic fever syndrome (characterized by widespread capillary leak and bleeding diathesis). **2. Analysis of Other Options:** * **Option A (Paramyxovirus):** This is true. Nipah virus belongs to the family *Paramyxoviridae*, genus *Henipavirus*. It is a pleomorphic, enveloped virus with a non-segmented, negative-sense RNA genome. * **Option C (Emerging Infection):** This is true. First identified in 1998 during an outbreak in Malaysia among pig farmers, it is classified by the WHO as a priority "emerging infectious disease" with high epidemic potential. * **Option D (Present in India):** This is true. India has faced multiple outbreaks, most notably in **Siliguri (2001)**, **Nadia (2007)**, and several recent recurrent outbreaks in **Kerala** (starting 2018). **Clinical Pearls for NEET-PG:** * **Natural Reservoir:** Fruit bats of the genus ***Pteropus*** (Flying foxes). * **Transmission:** Consumption of raw date palm sap contaminated by bat saliva/urine, contact with infected pigs (intermediate hosts), or human-to-human transmission via respiratory droplets. * **Diagnosis:** RT-PCR (from throat swabs, CSF, or urine) is the gold standard during the acute phase; ELISA for IgM/IgG is used later. * **Mortality:** Extremely high, ranging from **40% to 75%**. * **MRI Finding:** Characteristically shows small, discrete "confluent" lesions in the white matter.

Question 552: Chandipura virus multiplies in which of the following vectors?

A. Sandfly (Correct Answer)
B. Black fly
C. Simulum fly
D. Rat flea

Explanation: **Explanation:** **Chandipura Virus (CHPV)** is an emerging human pathogen belonging to the family **Rhabdoviridae** (Genus: *Vesiculovirus*). It is a significant cause of explosive outbreaks of acute encephalitis, particularly in children in India (notably in Maharashtra and Gujarat). **1. Why Sandfly is correct:** The primary vector for Chandipura virus is the **Sandfly** (specifically *Phlebotomus papatasi* and *Sergentomyia* species). The virus is transmitted to humans through the bite of an infected sandfly. It is unique among Rhabdoviruses for its rapid replication and high fatality rate in pediatric populations. **2. Why other options are incorrect:** * **Black fly (Simulium fly):** While Black flies are vectors for *Onchocerca volvulus* (River blindness) and certain animal Vesiculoviruses, they are not the vectors for Chandipura virus. Note: *Simulium* and Black fly are essentially the same entity (Option B and C). * **Rat flea:** *Xenopsylla cheopis* (the rat flea) is the classic vector for *Yersinia pestis* (Plague) and *Rickettsia typhi* (Endemic typhus), not viral encephalitis. **3. High-Yield Clinical Pearls for NEET-PG:** * **Family:** Rhabdoviridae (Bullet-shaped virus, same family as Rabies). * **Clinical Presentation:** Rapid onset of high-grade fever, altered sensorium, and convulsions, often progressing to coma and death within 24–48 hours. * **Target Population:** Primarily affects children under 15 years of age. * **Reservoir:** Likely small rodents or domestic animals, though the sandfly acts as both vector and a potential reservoir through transovarial transmission. * **Diagnosis:** Real-time PCR or ELISA for IgM antibodies. There is currently no specific antiviral treatment or vaccine.

Question 553: Condyloma accuminatum is caused by which virus?

A. Herpes Simplex Virus (HSV)
B. Human Papillomavirus (HPV) (Correct Answer)
C. Human Immunodeficiency Virus (HIV)
D. Varicella-Zoster Virus (VZV)

Explanation: **Explanation:** **Condyloma acuminatum**, commonly known as anogenital warts, is caused by the **Human Papillomavirus (HPV)**. It is a sexually transmitted infection characterized by cauliflower-like, flesh-colored growths in the perineal, perianal, and genital regions. 1. **Why HPV is correct:** HPV is a double-stranded DNA virus that infects basal keratinocytes. Specifically, **HPV types 6 and 11** (low-risk types) are responsible for approximately 90% of Condyloma acuminatum cases. These types cause benign cellular proliferation rather than malignancy. 2. **Why other options are incorrect:** * **Herpes Simplex Virus (HSV):** Causes painful, fluid-filled vesicles that rupture to form shallow ulcers (Herpes Genitalis), not warty growths. * **Human Immunodeficiency Virus (HIV):** While HIV increases the risk and severity of HPV infections due to immunosuppression, it does not directly cause condyloma. * **Varicella-Zoster Virus (VZV):** Causes Chickenpox (primary infection) and Herpes Zoster/Shingles (reactivation), presenting as dermatomal vesicular rashes. **NEET-PG High-Yield Pearls:** * **Condyloma Acuminatum vs. Condyloma Latum:** Do not confuse them. *Condyloma acuminatum* is viral (HPV), while *Condyloma latum* is a flat, moist lesion seen in Secondary Syphilis (*Treponema pallidum*). * **Histopathology:** The hallmark of HPV infection is **Koilocytosis** (cells with perinuclear halos and wrinkled "raisinoid" nuclei). * **Oncogenic Strains:** While types 6 and 11 cause warts, **HPV 16 and 18** are high-risk strains associated with Cervical, Anal, and Oropharyngeal Squamous Cell Carcinoma. * **Treatment:** Podophyllin, Imiquimod, or cryotherapy.

Question 554: Which of the following statements is true regarding the rabies virus?

A. Can be isolated from the blood of infected patients.
B. Has multiple antigenic types.
C. Can be transmitted by a dog 4 weeks before the dog becomes noticeably ill.
D. Produces infection that is almost fatal to humans. (Correct Answer)

Explanation: ### Explanation **Correct Option: D. Produces infection that is almost fatal to humans.** Rabies is a neurotropic virus belonging to the genus *Lyssavirus*. Once clinical symptoms (such as hydrophobia, aerophobia, or paralysis) manifest, the case fatality rate is virtually **100%**. The virus travels via retrograde axonal transport to the CNS, causing fulminant encephalomyelitis. Only a handful of survivors have ever been documented globally, usually involving the controversial "Milwaukee Protocol." **Why the other options are incorrect:** * **A. Isolation from blood:** Rabies virus is **not found in the blood** (no viremic phase). It is strictly neurotropic, spreading from the neuromuscular junction to the peripheral nerves and finally the CNS. Diagnosis is usually made via skin biopsy (nuchal area), saliva PCR, or post-mortem brain histology. * **B. Antigenic types:** The rabies virus has only **one serotype**. This is clinically significant because a single vaccine (derived from the PV or Pitman-Moore strain) provides universal protection against all classical rabies virus infections worldwide. * **C. Transmission window:** In dogs, the virus reaches the salivary glands only shortly before death. A dog can transmit the virus for a maximum of **3 to 10 days** before the onset of clinical symptoms or death. This is why the standard observation period for a suspected animal is 10 days. **High-Yield Clinical Pearls for NEET-PG:** * **Negri Bodies:** Pathognomonic intracytoplasmic eosinophilic inclusions found in neurons (most common in **Hippocampus/Pyramidal cells** and **Cerebellum/Purkinje cells**). * **Street Virus vs. Fixed Virus:** "Street virus" is the wild strain with long incubation; "Fixed virus" is laboratory-adapted with a short, fixed incubation period used for vaccine production. * **Post-Exposure Prophylaxis (PEP):** Includes wound washing (most critical step), Rabies Vaccine (Days 0, 3, 7, 14, 28), and Rabies Immunoglobulin (RIG) infiltrated into the wound.

Question 555: Epstein-Barr virus (EBV) is implicated in which of the following conditions, except?

A. Burkitt's lymphoma
B. Infectious mononucleosis
C. Slow virus disease (Correct Answer)
D. Lymphoma

Explanation: **Explanation:** The correct answer is **C. Slow virus disease**. **1. Why "Slow virus disease" is correct:** Slow virus diseases are characterized by a very long incubation period (months to years) and a progressive, usually fatal, clinical course. Classic examples include **Subacute Sclerosing Panencephalitis (SSPE)** caused by the Measles virus, **Progressive Multifocal Leukoencephalopathy (PML)** caused by the JC virus, and Prion diseases (like Kuru or Creutzfeldt-Jakob disease). **Epstein-Barr Virus (EBV)**, a member of the *Gammaherpesvirinae* subfamily, typically causes acute infections or latent infections that may lead to oncogenesis, but it is not classified as a "slow virus." **2. Why the other options are incorrect:** * **A & D. Burkitt's lymphoma / Lymphoma:** EBV is a potent oncogenic virus. It infects B-cells via the **CD21 receptor** and is strongly associated with African (endemic) Burkitt’s lymphoma (characterised by the t(8;14) translocation), Hodgkin’s lymphoma, and B-cell lymphomas in immunocompromised patients. * **B. Infectious mononucleosis:** This is the most common acute clinical manifestation of EBV, also known as "Glandular Fever" or "Kissing Disease." It is characterized by the triad of fever, pharyngitis, and lymphadenopathy, with the presence of **Atypical lymphocytes (Downey cells)** in the peripheral smear. **NEET-PG High-Yield Pearls:** * **Diagnosis:** The **Paul-Bunnell Test** (detecting heterophile antibodies) is the classic screening test for Infectious Mononucleosis. * **Other EBV Associations:** Nasopharyngeal carcinoma, Oral Hairy Leukoplakia (in HIV), and Gastric carcinoma. * **Receptor:** EBV uses the **CR2 (CD21)** receptor on B-cells and the MHC class II molecule as a co-receptor.

Question 556: What effect does a virus produce when it grows in cell culture?

A. Inhibition of cell metabolism
B. Immunofluorescence
C. Cytopathic effect
D. All of the above (Correct Answer)

Explanation: When a virus infects a host cell in culture, it hijacks the cellular machinery to replicate, leading to observable changes. The correct answer is **All of the above** because viral growth manifests through structural, metabolic, and detectable biochemical alterations. ### **Explanation of Options:** * **Cytopathic Effect (CPE):** This is the most common morphological evidence of viral growth. It includes structural changes such as cell rounding, shrinkage, lysis, or the formation of **syncytia** (multinucleated giant cells, e.g., RSV, Measles) and **inclusion bodies** (e.g., Negri bodies in Rabies). * **Inhibition of Cell Metabolism:** Viruses divert the cell's energy and synthetic pathways for their own replication. This often results in "cell shutdown," where host macromolecular synthesis (DNA, RNA, and protein) is inhibited, eventually leading to cell death. * **Immunofluorescence (IF):** While IF is a laboratory technique, it is used to detect the **expression of viral antigens** on the surface or within the cytoplasm/nucleus of the growing cells. A positive IF signal is a direct consequence of viral protein synthesis during growth in culture. ### **High-Yield Clinical Pearls for NEET-PG:** * **Detection Methods:** Other signs of viral growth include **Hemadsorption** (e.g., Influenza virus) and **Interference** (where a non-cytopathic virus prevents the growth of a second "challenger" virus). * **Inclusion Bodies:** * *Intranuclear:* Cowdry Type A (Herpes) and Owl’s eye (CMV). * *Intracytoplasmic:* Negri bodies (Rabies) and Guarnieri bodies (Smallpox). * **Gold Standard:** While molecular methods (PCR) are faster, **Cell Culture** remains the traditional "gold standard" for definitive viral isolation.

Question 557: SARS is caused by an organism having which of the following genetic material?

A. Single-stranded RNA (ssRNA) (Correct Answer)
B. Single-stranded DNA (ssDNA)
C. Double-stranded DNA (dsDNA)
D. Single-stranded DNA (ssDNA)

Explanation: **Explanation:** The Severe Acute Respiratory Syndrome (SARS) is caused by the **SARS-associated coronavirus (SARS-CoV)**. Coronaviruses belong to the family *Coronaviridae*, which are characterized by being **enveloped, positive-sense, single-stranded RNA (ssRNA) viruses** with a linear, non-segmented genome. This genome is one of the largest among RNA viruses (approx. 27–32 kb) and is surrounded by a helical nucleocapsid. **Analysis of Options:** * **Option A (Correct):** SARS-CoV is a positive-sense ssRNA virus. This means its RNA can function directly as mRNA within the host cell to initiate protein synthesis. * **Option B & D (Incorrect):** Single-stranded DNA (ssDNA) viruses are rare in human pathology; the most notable example is **Parvovirus B19**. * **Option C (Incorrect):** Double-stranded DNA (dsDNA) is the genetic material for families like *Herpesviridae*, *Adenoviridae*, and *Poxviridae*. While these cause significant respiratory or systemic infections, they are structurally distinct from Coronaviruses. **High-Yield Clinical Pearls for NEET-PG:** * **Morphology:** Coronaviruses have club-shaped surface projections (peplomers) giving a "crown-like" appearance under electron microscopy. * **Receptor:** SARS-CoV and SARS-CoV-2 both utilize the **ACE-2 (Angiotensin-Converting Enzyme 2)** receptor for cell entry. * **Zoonosis:** SARS-CoV originated in bats, with **masked palm civets** serving as the intermediate host. * **Other ssRNA Viruses:** Most "famous" respiratory viruses (Influenza, RSV, Measles, Mumps) are also RNA viruses, but Influenza is negative-sense and segmented.

Question 558: Which of the following best explains why hepatitis C is the most common cause of posttransfusion hepatitis?

A. Hepatitis C virus (HCV) carriers are highly prevalent in the general population, increasing the risk of transmission through blood donation.
B. Blood infected with hepatitis B virus (HBV) is not effectively eliminated by routine screening methods.
C. Current serologic tests for HCV fail to reliably exclude carriers.
D. Screening questions designed to identify and exclude individuals at risk for HCV from the blood donor pool lack sufficient specificity. (Correct Answer)

Explanation: **Explanation:** Hepatitis C Virus (HCV) remains the leading cause of post-transfusion hepatitis primarily due to the limitations of **donor deferral strategies**. While modern laboratory screening (NAT and ELISA) has significantly reduced the "window period" risk, the initial line of defense—the donor history questionnaire—lacks the **specificity** to accurately identify all high-risk individuals. Many HCV-infected individuals do not belong to traditional high-risk groups or may not disclose risky behaviors, allowing them to enter the donor pool. **Analysis of Options:** * **Option D (Correct):** The screening questions are often broad or subjective. Because HCV is frequently asymptomatic for decades, donors may be unaware of their status, and the screening process cannot specifically filter out every potential carrier based on history alone. * **Option A:** While HCV is prevalent, HBV actually has a higher global carrier rate. The reason HCV dominates post-transfusion cases is not just prevalence, but the difficulty in total elimination from the blood supply compared to HBV. * **Option B:** This is incorrect. Routine screening for HBsAg and anti-HBc is highly effective, making the risk of transfusion-transmitted HBV extremely low (approx. 1 in 1 million units). * **Option C:** Modern Nucleic Acid Testing (NAT) is highly sensitive and can detect HCV RNA within 1–2 weeks of infection. The failure is rarely the test's reliability, but rather the rare "window period" cases or donor selection lapses. **NEET-PG High-Yield Pearls:** * **Most common cause of post-transfusion hepatitis:** Hepatitis C (Non-A, Non-B). * **Risk of Chronicity:** HCV has the highest rate of progression to chronic infection (~70-80%). * **Screening:** Blood banks use **ELISA** for antibodies and **NAT (Nucleic Acid Testing)** for viral RNA to minimize the window period. * **Hepatitis B:** Most common cause of post-transfusion hepatitis *historically*, before the advent of HBsAg screening.

Question 559: Which co-receptor is utilized by the R5 variant of the Human Immunodeficiency Virus?

A. Integrin
B. CCR5 (Correct Answer)
C. CXCR4
D. p53

Explanation: **Explanation:** The entry of HIV into host cells is a multi-step process involving the viral envelope glycoprotein **gp120**. Initially, gp120 binds to the **CD4 receptor** on T-lymphocytes or macrophages. However, for successful fusion and entry, a secondary binding with a **co-receptor** is mandatory. * **CCR5 (Correct Answer):** The **R5 variant** (Macrophage-tropic or M-tropic) utilizes the **CCR5** chemokine receptor. These variants are typically responsible for the initial infection and are found predominantly on macrophages and memory T-cells. Individuals with a homozygous **CCR5-Δ32 mutation** are naturally resistant to HIV infection. * **CXCR4 (Option C):** This co-receptor is used by the **X4 variant** (T-tropic). These variants usually emerge in the later stages of the disease, lead to rapid CD4+ T-cell decline, and signal progression to AIDS. * **Integrin (Option A):** While some integrins (like α4β7) may facilitate HIV binding in the gut-associated lymphoid tissue (GALT), they are not the primary co-receptors defining the R5 or X4 tropism. * **p53 (Option D):** This is a tumor suppressor protein ("guardian of the genome") involved in cell cycle regulation and apoptosis; it plays no role as a viral entry co-receptor. **High-Yield Clinical Pearls for NEET-PG:** 1. **Maraviroc:** A CCR5 antagonist drug that prevents viral entry by blocking the R5 co-receptor. 2. **Tropism Switch:** The progression from asymptomatic HIV to AIDS is often marked by a "switch" from R5 (M-tropic) to X4 (T-tropic) variants. 3. **gp41:** While gp120 handles attachment, the transmembrane protein **gp41** is responsible for the actual fusion of the viral envelope with the host cell membrane.

Question 560: What cancer is associated with Cytomegalovirus infection in patients with AIDS?

A. Lymphoma (Correct Answer)
B. Kaposi sarcoma
C. Leukemia
D. Glioma

Explanation: **Explanation:** **Cytomegalovirus (CMV)**, a member of the *Betaherpesvirinae* family, is a significant opportunistic pathogen in immunocompromised individuals, particularly those with AIDS. While CMV is most commonly associated with retinitis, pneumonitis, and colitis, it also plays a role in oncogenesis. In the context of AIDS, CMV infection is strongly associated with the development of **Non-Hodgkin Lymphoma (NHL)**. The virus acts as a co-factor in lymphomagenesis by promoting chronic B-cell activation and inhibiting apoptosis, which facilitates the malignant transformation of lymphocytes. **Analysis of Options:** * **A. Lymphoma (Correct):** CMV is linked to B-cell lymphomas in AIDS patients. It acts synergistically with other factors (like EBV) to drive lymphoid malignancy. * **B. Kaposi Sarcoma:** This is caused by **Human Herpesvirus 8 (HHV-8)**, not CMV. While both are common in AIDS patients, the etiologic agent is distinct. * **C. Leukemia:** There is no established direct causal link between CMV infection and the development of leukemia in AIDS patients. * **D. Glioma:** While CMV DNA has been detected in some glioblastomas, it is not the primary cancer associated with CMV in the specific context of AIDS-related opportunistic malignancies. **Clinical Pearls for NEET-PG:** * **CMV Retinitis:** The most common clinical manifestation of CMV in AIDS (CD4 count <50 cells/mm³); characterized by "pizza-pie" or "cheese and ketchup" fundus. * **Inclusion Bodies:** Look for **"Owl’s eye"** intranuclear inclusions on histopathology. * **Drug of Choice:** Ganciclovir is the first-line treatment; Foscarnet is used for resistant cases. * **Congenital CMV:** Most common viral cause of congenital sensorineural hearing loss and mental retardation.

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