Virology Practice Questions

Q: Swine flu is caused by which influenza virus subtype?

H1N1. **Explanation:** **Correct Answer: A. H1N1** Swine flu is caused by the **Influenza A virus subtype H1N1**. The 2009 pandemic was specifically caused by a triple-reassortant strain containing genetic material from human, avian, and swine influenza viruses. The nomenclature refers to the two primary surface glycoproteins: **Hemagglutinin (H)**, which facilitates viral entry into host cells, and **Neuraminidase (N)**, which assists in the release of new virions. **Analysis of Incorrect Options:** * **B. H5N1:** This is the primary subtype responsible for **Avian Influenza (Bird Flu)**. It is highly pathogenic in birds and can cause severe respiratory disease in humans with a high mortality rate, though human-to-human transmission is inefficient. * **C. H3N1:** While H3 subtypes exist (like H3N2, a common seasonal flu), H3N1 is not a major human pathogen and is typically associated with veterinary infections (e.g., in pigs) without widespread human outbreaks. * **D. H3N3:** This is a rare subtype primarily found in wild birds and does not cause significant human disease or the clinical syndrome known as Swine Flu. **High-Yield Clinical Pearls for NEET-PG:** * **Antigenic Shift:** Major genetic changes (reassortment) leading to new subtypes; responsible for **Pandemics**. * **Antigenic Drift:** Minor point mutations in H or N genes; responsible for **Epidemics** and the need for annual vaccine updates. * **Drug of Choice:** **Oseltamivir** (Tamiflu), a neuraminidase inhibitor, is the preferred treatment for H1N1. * **Diagnosis:** **Real-time RT-PCR** of nasopharyngeal swabs is the gold standard for confirmation.

Q: Which is the confirmatory test for HIV infection?

Western Blot. **Explanation:** The diagnosis of HIV infection follows a specific algorithm: a highly sensitive screening test followed by a highly specific confirmatory test. **1. Why Western Blot is Correct:** Western Blot is considered the gold standard **confirmatory test** for HIV. It detects specific antibodies against individual viral proteins (Antigens). For a result to be positive, antibodies must be present against at least two of the following three gene products: **p24** (gag), **gp41** (env), and **gp120/160** (env). Its high specificity ensures that false positives from screening tests are eliminated. **2. Why other options are incorrect:** * **ELISA (Enzyme-Linked Immunosorbent Assay):** This is the standard **screening test**. It is highly sensitive but can yield false positives due to cross-reactivity (e.g., in autoimmune diseases or recent vaccinations). * **Immunodot (Rapid Test):** These are simple, rapid screening tests used in bedside settings or peripheral centers. Like ELISA, they require confirmation. * **RIPA (Radioimmunoprecipitation Assay):** While highly specific and sensitive, it is technically demanding, expensive, and primarily used in research settings rather than routine clinical confirmation. **Clinical Pearls for NEET-PG:** * **Window Period:** The time between infection and the appearance of detectable antibodies (usually 2–8 weeks). * **Screening vs. Confirmation:** ELISA is for screening (high sensitivity); Western Blot is for confirmation (high specificity). * **Diagnosis in Infants:** In children <18 months, maternal antibodies persist; therefore, **PCR (DNA PCR for proviral DNA)** is the investigation of choice, not antibody tests. * **Recent Shift:** Current NACO guidelines and newer CDC algorithms often utilize a "Repeated ELISA" or "4th Generation p24 Antigen-Antibody Combo" approach, but for exam purposes, Western Blot remains the classic confirmatory answer.

Q: Which of the following statements regarding Cytomegalovirus (CMV) is FALSE?

Foscarnet can completely eliminate CMV infection.. **Explanation:** The correct answer is **C**, as no current antiviral therapy, including Foscarnet, can completely eliminate Cytomegalovirus (CMV) from the body. **Why Option C is False:** CMV is a member of the *Herpesviridae* family. Like all herpesviruses, CMV establishes **lifelong latency** in the host (specifically in monocytes, macrophages, and CD34+ hematopoietic progenitor cells). Antiviral drugs like Ganciclovir, Foscarnet, and Cidofovir inhibit viral DNA polymerase and stop active replication, but they cannot eradicate the latent viral genome. Therefore, the infection is suppressed, not eliminated. **Analysis of Other Options:** * **Option A:** CMV is indeed a **double-stranded DNA (dsDNA)** virus, belonging to the Beta-herpesvirus subfamily. * **Option B:** In immunocompetent individuals, primary CMV infection is usually asymptomatic or presents as a self-limiting **mononucleosis-like syndrome** (Heterophile antibody negative). * **Option D:** CMV retinitis is an AIDS-defining illness. It typically occurs as an opportunistic infection when the **CD4 count falls below 50–100 cells/mm³**. It is extremely rare in patients with a CD4 count >200 cells/mm³. **High-Yield Clinical Pearls for NEET-PG:** * **Histology:** Look for **"Owl’s Eye" intranuclear inclusion bodies** (large cells with clear halos around the nucleus). * **Congenital CMV:** Most common viral cause of congenital defects; characterized by periventricular calcifications, microcephaly, and sensorineural hearing loss. * **Treatment of Choice:** **Ganciclovir** is the first-line agent. **Foscarnet** is used for ganciclovir-resistant strains but is limited by nephrotoxicity. * **Transplant Medicine:** CMV is the most common viral infection complicating solid organ transplants.

Q: Heterophile antibody test is done for:

Infectious mononucleosis. **Explanation:** **Infectious Mononucleosis (IM)**, primarily caused by the **Epstein-Barr Virus (EBV)**, is characterized by the production of **heterophile antibodies**. These are IgM antibodies produced due to polyclonal B-cell activation that do not react with EBV antigens but instead agglutinate red blood cells from other species (sheep, horse, or ox). The **Paul-Bunnell test** and the rapid **Monospot test** detect these antibodies, making them the diagnostic gold standard for IM in adolescents and adults. **Analysis of Incorrect Options:** * **A. Rickettsial infections:** These are diagnosed using the **Weil-Felix test**. While this is also a heterophile antibody test, it specifically uses *Proteus* antigens ($OX19, OX2, OXK$) to detect cross-reacting antibodies against Rickettsia. * **C. Smallpox:** Diagnosis was historically made via clinical presentation, electron microscopy, or viral culture (Guarnieri bodies). Heterophile tests play no role here. * **D. Japanese encephalitis:** This is a Flavivirus infection diagnosed primarily through **IgM Capture ELISA** (MAC-ELISA) of the CSF or serum. **High-Yield Clinical Pearls for NEET-PG:** * **Paul-Bunnell Test:** Uses sheep RBCs. A titer of 1:56 or higher is considered significant. * **Differential Diagnosis:** If a patient has IM-like symptoms (fever, sore throat, lymphadenopathy) but is **Heterophile Negative**, consider **Cytomegalovirus (CMV)**, which is the most common cause of heterophile-negative mononucleosis. * **Peripheral Smear:** Look for **Downey cells** (atypical T-lymphocytes) which are characteristic of EBV infection. * **Ampicillin Rash:** Patients with EBV mononucleosis often develop a maculopapular rash if treated with Ampicillin or Amoxicillin.

Q: Epstein-Barr virus (EBV) causes which of the following conditions?

Pancreatic carcinoma. **Explanation:** The question asks to identify which condition is **NOT** typically associated with Epstein-Barr Virus (EBV), as Pancreatic carcinoma is the "odd one out" in this clinical context. **1. Why Pancreatic Carcinoma is the Correct Answer (The Exception):** Epstein-Barr Virus (EBV), a γ-herpesvirus (HHV-4), is known for its strong association with various B-cell and epithelial malignancies. However, **Pancreatic carcinoma** has no established causal link with EBV. Pancreatic cancer is primarily associated with smoking, chronic pancreatitis, and mutations in the KRAS, CDKN2A, TP53, and SMAD4 genes, rather than viral oncogenesis. **2. Analysis of Incorrect Options (Associations with EBV):** * **Glandular Fever (Infectious Mononucleosis):** This is the primary clinical manifestation of EBV infection, characterized by the triad of fever, pharyngitis, and lymphadenopathy. It is diagnosed via the Paul-Bunnell test (heterophile antibodies). * **Burkitt’s Lymphoma:** EBV is strongly linked to the African (endemic) variant of Burkitt’s lymphoma, characterized by the **t(8;14)** translocation involving the c-myc oncogene. * **Nasopharyngeal Carcinoma:** This is an epithelial tumor highly prevalent in Southern China, where EBV DNA is consistently found within the tumor cells. **3. High-Yield Clinical Pearls for NEET-PG:** * **Receptor:** EBV binds to the **CD21** receptor (CR2) on B-cells and the MHC class II molecule. * **Hematology:** Peripheral smear shows **Atypical Lymphocytes (Downey cells)**, which are actually activated T-cells (CD8+) reacting against infected B-cells. * **Other Associations:** Oral Hairy Leukoplakia (in HIV patients), Hodgkin’s Lymphoma (Mixed cellularity subtype), and Gastric Carcinoma (approx. 10% of cases). * **Diagnosis:** Monospot test is the screening test of choice; VCA-IgM (Viral Capsid Antigen) indicates acute infection.

Q: A mother presents to the neonatology OPD with her baby because of yellow extremities. On examination, there is a petechial rash over the body, hepatosplenomegaly, and microcephaly. What is the causative organism?

Cytomegalovirus (CMV). ### Explanation The clinical presentation described—**jaundice** (yellow extremities), **petechial rash** (often referred to as a "blueberry muffin" rash), **hepatosplenomegaly**, and **microcephaly**—is the classic tetrad of **Congenital Cytomegalovirus (CMV) infection**. CMV is the most common intrauterine infection worldwide. **Why Option A is Correct:** CMV is the leading cause of sensorineural hearing loss and mental retardation among the TORCH infections. The presence of **periventricular calcifications** (though not mentioned here) and microcephaly are hallmark neurological findings. The petechial rash occurs due to thrombocytopenia and extramedullary hematopoiesis. **Why Other Options are Incorrect:** * **B. Rubella virus:** While it also presents with a "blueberry muffin" rash and hepatosplenomegaly, the classic triad for Congenital Rubella Syndrome (Gregg’s Triad) includes **Cataracts, PDA (Cardiac defects), and Sensorineural deafness**. * **C. Herpes Simplex Virus (HSV):** Neonatal HSV typically presents in the first few weeks of life (not necessarily at birth) with **Skin-Eye-Mouth (SEM) vesicles**, encephalitis, or disseminated multi-organ failure. * **D. Varicella-Zoster Virus (VZV):** Congenital Varicella Syndrome is characterized by **cicatricial skin scarring** (zigzag patterns) and limb hypoplasia, rather than the generalized petechial rash seen here. **NEET-PG High-Yield Pearls:** * **Most common finding in CMV:** Most infants are asymptomatic at birth; however, **Sensorineural Hearing Loss (SNHL)** is the most common long-term sequela. * **Imaging:** CMV shows **periventricular** calcifications, whereas Toxoplasmosis shows **diffuse** intracerebral calcifications. * **Diagnosis:** Gold standard is **Viral culture or PCR of urine/saliva** within the first 3 weeks of life. * **Histology:** Look for "Owl’s eye" intranuclear inclusion bodies.

Q: All of the following are caused by RNA viruses, EXCEPT:

Fifth disease. **Explanation:** The core concept tested here is the classification of viruses based on their genetic material. **Correct Answer: D. Fifth Disease** Fifth disease (also known as Erythema Infectiosum) is caused by **Parvovirus B19**. Parvovirus is a **DNA virus**. Specifically, it is unique for being a **non-enveloped, single-stranded DNA (ssDNA)** virus. In the NEET-PG context, remembering that "Parvo" is the only medically significant ssDNA virus is a high-yield fact. **Why the other options are incorrect:** * **A. HIV:** This is a Retrovirus. It contains two copies of single-stranded **RNA** (ssRNA) and uses reverse transcriptase to integrate into the host genome. * **B. Dengue:** Caused by the Dengue virus, which belongs to the *Flaviviridae* family. All Flaviviruses are enveloped, positive-sense **ssRNA** viruses. * **C. Herpangina:** Despite the name sounding like "Herpes" (which is DNA), Herpangina is caused by **Coxsackievirus A**, a member of the *Picornaviridae* family. All Picornaviruses are non-enveloped **ssRNA** viruses. **Clinical Pearls for NEET-PG:** 1. **Fifth Disease Presentation:** Characterized by the "slapped-cheek" rash and can cause aplastic crisis in patients with sickle cell anemia or hereditary spherocytosis. 2. **DNA Virus Mnemonic:** Remember **"HHAPPPPy"** viruses (Herpes, Hepadna, Adeno, Papilloma, Polyoma, Pox, Parvo). All are double-stranded except Parvo (ssDNA). 3. **Herpangina vs. Herpes:** Herpangina (Coxsackie) typically causes vesicles on the **posterior** pharynx/soft palate, whereas Herpetic Gingivostomatitis (HSV-1) involves the **anterior** mouth and gums.

Q: The Paul-Bunnell test is positive in which of the following conditions?

Infectious mononucleosis. **Explanation:** The **Paul-Bunnell test** is a classic diagnostic test used to detect **Infectious Mononucleosis (IM)**, caused by the **Epstein-Barr Virus (EBV)**. **1. Why Infectious Mononucleosis is correct:** In response to an EBV infection, the body produces **heterophile antibodies**. These are IgM antibodies that do not react with EBV antigens themselves but have the unique property of agglutinating red blood cells (RBCs) from other species, such as sheep, horse, or ox RBCs. The Paul-Bunnell test specifically uses **sheep RBCs**; a positive result (agglutination) confirms the presence of these heterophile antibodies, which are highly specific for IM in the clinical context of fever, pharyngitis, and lymphadenopathy. **2. Why other options are incorrect:** * **Multiple myeloma:** This is a plasma cell dyscrasia characterized by monoclonal (M) protein spikes, not heterophile antibodies. * **Malignant neoplasms:** While EBV is associated with malignancies like Burkitt lymphoma and Nasopharyngeal carcinoma, the Paul-Bunnell test is only positive during the acute phase of primary infection (IM), not the subsequent malignancies. * **Rubella:** This viral infection presents with a rash and lymphadenopathy but does not induce the production of heterophile antibodies. **High-Yield Clinical Pearls for NEET-PG:** * **Differential Diagnosis:** If a patient has IM-like symptoms but the Paul-Bunnell test is **negative**, consider **CMV infection** (the most common cause of heterophile-negative mononucleosis). * **Monospot Test:** A modern, rapid version of the Paul-Bunnell test using horse RBCs. * **Davidsohn Differential Test:** Used to distinguish IM antibodies from Forssman antibodies and serum sickness antibodies using guinea pig kidney extract and beef RBCs. * **Hematology:** Look for **atypical lymphocytes (Downey cells)** on a peripheral smear.

Q: Hep-2 cells are a type of:

Continuous cell lines. **Explanation:** Cell cultures are classified into three types based on their origin, chromosomal characteristics, and number of divisions. **Hep-2 (Human Epithelioma type 2)** cells are derived from a human laryngeal carcinoma. Because they are derived from cancerous tissue, they are immortalized and can be subcultured indefinitely, making them a **Continuous Cell Line**. **Why the correct answer is right:** * **Continuous Cell Lines (Option C):** These are derived from cancer cells or by transforming normal cells. They are **heteroploid** (abnormal number of chromosomes), rapid-growing, and can be maintained through serial subculturing for an infinite number of generations. Hep-2 is a classic example used widely in virology and immunology. **Why the other options are wrong:** * **Primary Cell Cultures (Option A):** These are normal cells freshly taken from an organ (e.g., Monkey Kidney, Chick Embryo). They can only be subcultured once or twice before dying. * **Diploid Cell Strains (Option B):** These are fibroblast cells (e.g., WI-38, HL-8) that maintain a diploid chromosome number. They can be subcultured about 50 times before undergoing senescence. They are preferred for vaccine production. * **Explant Culture (Option D):** This involves growing small fragments of tissue (explants) directly on a surface, rather than dissociated cells. **High-Yield Facts for NEET-PG:** * **Hep-2 uses:** Traditionally used for isolating Respiratory Syncytial Virus (RSV), Adenovirus, and Enteroviruses. In immunology, it is the "gold standard" substrate for **ANA (Antinuclear Antibody)** testing via Indirect Immunofluorescence. * **Other Continuous Lines:** HeLa (Cervical cancer), Vero (Vervet monkey kidney), BHK-21 (Baby Hamster Kidney). * **Vaccine Production:** Human Diploid cells (WI-38, MRC-5) are used for producing vaccines like Rabies and Rubella because they are free from oncogenic potential.

Question 1

Swine flu is caused by which influenza virus subtype?

Accepted Answer

H1N1

Answer

H5N1

Answer

H3N1

Answer

H3N3

Question 2

Which is the confirmatory test for HIV infection?

Accepted Answer

Western Blot

Answer

ELISA

Answer

Immunodot

Answer

RIPA

Question 3

Which of the following statements regarding Cytomegalovirus (CMV) is FALSE?

Accepted Answer

Foscarnet can completely eliminate CMV infection.

Answer

CMV is a double-stranded DNA virus.

Answer

CMV rarely causes significant problems in immunocompetent individuals.

Answer

CMV retinitis is rare when the CD4 count is greater than 200 cells/mm³.

Question 4

Heterophile antibody test is done for:

Accepted Answer

Infectious mononucleosis

Answer

Rickettsial infections

Answer

Smallpox

Answer

Japanese encephalitis

Question 5

Epstein-Barr virus (EBV) causes which of the following conditions?

Accepted Answer

Pancreatic carcinoma

Answer

Glandular fever

Answer

Burkitt's lymphoma

Answer

Nasopharyngeal carcinoma

Question 6

A mother presents to the neonatology OPD with her baby because of yellow extremities. On examination, there is a petechial rash over the body, hepatosplenomegaly, and microcephaly. What is the causative organism?

Accepted Answer

Cytomegalovirus (CMV)

Answer

Rubella virus

Answer

Herpes Simplex Virus (HSV)

Answer

Varicella-Zoster Virus (VZV)

Question 7

All of the following are caused by RNA viruses, EXCEPT:

Accepted Answer

Fifth disease

Answer

HIV

Answer

Dengue

Answer

Herpangina

Question 8

The Paul-Bunnell test is positive in which of the following conditions?

Accepted Answer

Infectious mononucleosis

Answer

Multiple myeloma

Answer

Malignant neoplasms

Answer

Rubella

Question 9

An elderly male presents with fever, cough, and shortness of breath for 2 weeks. He has a history of chronic bronchitis and diabetes, and recent travel to Wuhan City, China. What is the symmetry of the causative virus?

Accepted Answer

Enveloped helical symmetry

Answer

Naked helical symmetry

Answer

Complex symmetry

Answer

Icosahedral symmetry

Question 10

Hep-2 cells are a type of:

Accepted Answer

Continuous cell lines

Answer

Primary cell cultures

Answer

Diploid cell strain

Answer

Explant culture

Virology — MCQs

Virology — MCQs

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