Virology Practice Questions

Q: Which of the following is an oncogenic RNA virus?

Hepatitis C virus. **Explanation:** The core concept tested here is the classification of oncogenic viruses based on their genetic material (DNA vs. RNA). **Correct Answer: D. Hepatitis C virus (HCV)** Hepatitis C is a member of the *Flaviviridae* family and is a **single-stranded RNA virus**. It is a major cause of chronic hepatitis, cirrhosis, and **Hepatocellular Carcinoma (HCC)**. Unlike most oncogenic viruses, HCV does not integrate its genome into the host DNA; instead, it promotes carcinogenesis through chronic inflammation, oxidative stress, and the action of non-structural proteins (like NS5A) that interfere with cell cycle regulation. **Incorrect Options:** * **A. Hepatitis B virus (HBV):** While it causes HCC, it is a **dsDNA virus** (Hepadnaviridae). It integrates into the host genome and produces the HBx protein, which inactivates the p53 tumor suppressor. * **B. Human Papilloma Virus (HPV):** This is a **dsDNA virus**. High-risk types (16, 18) cause cervical and oropharyngeal cancers via E6 and E7 oncoproteins, which inhibit p53 and pRb respectively. * **C. Epstein-Barr Virus (EBV):** This is a **dsDNA virus** (Herpesviridae). It is associated with Burkitt lymphoma, Nasopharyngeal carcinoma, and Hodgkin lymphoma. **High-Yield Clinical Pearls for NEET-PG:** * **Oncogenic RNA Viruses:** Only two are majorly recognized: **HCV** and **HTLV-1** (Human T-cell Lymphotropic Virus type 1, which causes Adult T-cell Leukemia/Lymphoma). * **Direct vs. Indirect:** HTLV-1 is a direct transforming virus (contains oncogenes), while HCV is considered an indirect carcinogen (mediated by chronic injury). * **Mnemonic:** Most oncogenic viruses are DNA viruses (HBV, HPV, EBV, HHV-8, MCV) EXCEPT for HCV and HTLV-1.

Q: A 45-year-old male presents for an HIV test. He reports unprotected sexual contact with another man three weeks prior. Antibodies against which of the following viral components will be detected first by ELISA or Western blot?

gp41. **Explanation:** The correct answer is **gp41**. In the natural course of HIV infection, the immune system produces antibodies against various viral proteins. Among these, **anti-gp41 antibodies** are the first to appear and reach detectable levels by conventional ELISA or Western blot, typically within 3–4 weeks of infection. **Why gp41 is correct:** * **gp41 (Transmembrane protein):** It is highly immunogenic. During the "seroconversion" phase, antibodies against the envelope proteins (gp41 and gp120) develop early. Specifically, anti-gp41 is the earliest antibody detected by standard diagnostic assays. **Analysis of Incorrect Options:** * **p24 (Capsid protein):** While the **p24 antigen** itself is the first viral marker to appear in the blood (detected by 4th generation ELISA during the window period), the **antibody** against p24 usually appears slightly after anti-gp41. * **gp120 (Surface protein):** Antibodies to gp120 develop early alongside gp41, but they generally reach detectable thresholds later than anti-gp41. * **p55:** This is a precursor polypeptide (Gag precursor) that is cleaved into p24, p17, and p7. It is not a primary target for early diagnostic antibody detection. **NEET-PG High-Yield Pearls:** 1. **Sequence of Markers:** RNA (7-10 days) → p24 Antigen (14-16 days) → Antibodies (3-4 weeks). 2. **Window Period:** The time between infection and the appearance of detectable antibodies. 4th generation ELISA (p24 Ag + Ab) has significantly shortened this. 3. **Western Blot Criteria:** A positive result requires antibodies against at least two of the following: **p24, gp41, or gp120/160**. 4. **Screening vs. Confirmatory:** ELISA is the screening test of choice (high sensitivity), while Western Blot is the traditional confirmatory test (high specificity).

Q: Which virus has a wheel-like shape?

Rotavirus. **Explanation:** The correct answer is **Rotavirus**. The name "Rotavirus" is derived from the Latin word **"Rota,"** which means **wheel**. Under electron microscopy, the virus exhibits a characteristic appearance resembling a wheel with a distinct rim and radiating spokes. This unique morphology is due to its triple-layered icosahedral protein capsid (outer, middle, and inner layers). **Analysis of Options:** * **Tobacco mosaic virus:** This is a plant virus characterized by a **rod-shaped** (helical) symmetry. * **Adenovirus:** This is a non-enveloped DNA virus with an **icosahedral** shape. It is famously described as looking like a **"space satellite"** or a "soccer ball" due to the fibers (pentons) projecting from its vertices. * **Rabies virus:** This virus belongs to the Rhabdoviridae family and has a classic **bullet-shaped** morphology. **High-Yield Clinical Pearls for NEET-PG:** * **Family:** Reoviridae. * **Genome:** Double-stranded RNA (dsRNA), which is **segmented** (11 segments). * **Clinical Significance:** Rotavirus is the most common cause of severe, dehydrating **diarrhea in infants and young children** worldwide. * **Pathogenesis:** It produces an enterotoxin called **NSP4**, which induces secretory diarrhea by increasing intracellular calcium. * **Diagnosis:** Most commonly diagnosed via detection of viral antigen in stool using **ELISA** or Latex Agglutination. * **Vaccines:** Live attenuated oral vaccines (e.g., Rotarix, RotaTeq) are part of the Universal Immunization Programme (UIP).

Q: Hand, foot, and mouth disease is caused by which virus?

Enterovirus 71. **Explanation:** **Hand, Foot, and Mouth Disease (HFMD)** is a common viral illness, primarily affecting children, characterized by fever and vesicular eruptions on the palms, soles, and oral mucosa. **1. Why Enterovirus 71 is correct:** HFMD is most commonly caused by viruses belonging to the *Picornaviridae* family, specifically the genus *Enterovirus*. The two most frequent causative agents are **Coxsackievirus A16** (the most common cause globally) and **Enterovirus 71 (EV-71)**. EV-71 is particularly significant in medical exams because it is associated with more severe clinical manifestations, including neurological complications like aseptic meningitis, encephalitis, and acute flaccid paralysis. **2. Why the other options are incorrect:** * **Enterovirus 70:** This virus is the primary cause of **Acute Hemorrhagic Conjunctivitis (AHC)**, often occurring in large epidemics. * **Enterovirus 72:** This was the former taxonomic designation for **Hepatitis A virus**. It causes acute infectious hepatitis, not vesicular skin rashes. * **Enterovirus 68:** This is primarily a **respiratory pathogen** associated with severe lower respiratory tract infections and, occasionally, acute flaccid myelitis (AFM) in children. **Clinical Pearls for NEET-PG:** * **Transmission:** Fecal-oral route and respiratory droplets. * **Clinical Triad:** Ulcers in the mouth (herpangina-like) + Maculopapular/vesicular rash on hands and feet. * **Complications:** While Coxsackie A16 is usually self-limiting, **EV-71** is the high-yield "danger" subtype linked to brainstem encephalitis and pulmonary edema. * **Differential Diagnosis:** Do not confuse HFMD with "Foot and Mouth Disease" (Aphthovirus), which affects cattle and rarely humans.

Q: Which of the following viruses, in addition to HSV-1 and HSV-2, produces the cytopathologic finding of multinucleated giant cells?

Varicella-zoster virus. **Explanation:** The hallmark cytopathologic finding for certain herpesviruses is the formation of **multinucleated giant cells** with intranuclear inclusion bodies (Cowdry type A). This occurs due to the fusion of infected host cell membranes, a process mediated by viral glycoproteins. **Why Varicella-zoster virus (VZV) is correct:** VZV, like HSV-1 and HSV-2, belongs to the **Alphaherpesvirinae** subfamily. These viruses share the characteristic of inducing cell-to-cell fusion (syncytia). A **Tzanck smear** performed on scrapings from the base of a vesicle will show these characteristic multinucleated giant cells in infections caused by HSV-1, HSV-2, and VZV. **Why other options are incorrect:** * **Adenovirus:** Typically produces "smudge cells" (large, dark intranuclear inclusions) but does not form multinucleated giant cells. * **Cytomegalovirus (CMV):** While it causes cell enlargement (cytomegaly), its classic finding is a single, large "Owl’s eye" intranuclear inclusion. It does not typically present with multinucleation on a Tzanck smear. * **Human papillomavirus (HPV):** Characterized by **koilocytes** (squamous epithelial cells with perinuclear halos and wrinkled nuclei), not multinucleated giant cells. **High-Yield NEET-PG Pearls:** * **Tzanck Smear:** Used for rapid bedside diagnosis of HSV and VZV. It identifies multinucleated giant cells but *cannot* distinguish between HSV-1, HSV-2, and VZV. * **Cowdry Type A Inclusions:** Eosinophilic nuclear inclusions surrounded by a clear halo; seen in HSV and VZV. * **Syncytia Formation:** Also a key feature of Paramyxoviruses (like Measles and RSV) and HIV, but in the context of vesicular skin rashes, always think of the Alpha-herpes family.

Q: A child who has undergone a kidney transplant develops lymphoproliferative cancer. This is associated with which viral infection?

Epstein-Barr virus (EBV). **Explanation:** The correct answer is **Epstein-Barr virus (EBV)**. This condition is known as **Post-Transplant Lymphoproliferative Disorder (PTLD)**. **Why EBV is correct:** In transplant recipients, the administration of potent immunosuppressive drugs (to prevent graft rejection) leads to a significant reduction in **T-cell mediated immunity**. EBV naturally infects B-lymphocytes and remains latent. Without T-cell surveillance (specifically Cytotoxic T-lymphocytes), EBV-infected B-cells undergo uncontrolled proliferation, driven by viral oncogenes like **LMP-1**. This can progress from benign polyclonal B-cell hyperplasia to malignant monoclonal B-cell lymphoma. **Why other options are incorrect:** * **Cytomegalovirus (CMV):** While CMV is the most common viral infection post-transplant, it typically causes fever, pneumonia, or retinitis, rather than lymphoproliferative cancer. * **Varicella-zoster virus (VZV):** Causes chickenpox or shingles. In transplant patients, it can lead to disseminated disease, but it is not oncogenic. * **Human papillomavirus (HPV):** Associated with cervical, anogenital, and oropharyngeal cancers, but not typically with systemic lymphoproliferative disorders in the context of acute post-transplant immunosuppression. **High-Yield NEET-PG Pearls:** * **EBV Association:** Also linked to Burkitt Lymphoma (t(8;14)), Nasopharyngeal Carcinoma, and Hodgkin Lymphoma. * **PTLD Management:** The first step in management is often the **reduction of immunosuppressive therapy** to allow the patient’s immune system to regain control over the B-cell proliferation. * **Diagnosis:** Elevated EBV viral load (via PCR) and biopsy showing B-cell expansion (CD20+).

Q: Which of the following statements regarding Hepatitis B virus (HBV) and Hepatitis D virus (HDV) is false?

Both are DNA viruses. **Explanation:** The correct answer is **D** because it is a factually incorrect statement. **Hepatitis B Virus (HBV)** is a partially double-stranded **DNA virus** (Hepadnaviridae), whereas **Hepatitis D Virus (HDV)** is a defective **RNA virus**. HDV requires the surface antigen (HBsAg) of HBV to provide its envelope for assembly and transmission. **Analysis of other options:** * **Option A (Both can infect simultaneously):** This is true and is termed **Co-infection**. It typically presents as acute hepatitis and often results in recovery, with a low risk of chronicity. * **Option B (HDV causes more serious infection due to superinfection):** This is true. **Superinfection** occurs when a chronic HBV carrier is later infected with HDV. This leads to a much higher risk of fulminant hepatitis, rapid progression to cirrhosis, and a high rate of chronic HDV infection. * **Option C (HDV cannot infect in the absence of HBV):** This is true. HDV is a "satellite" or defective virus; it lacks the genes to produce its own coat protein and must "borrow" HBsAg from HBV to infect other cells. **High-Yield Clinical Pearls for NEET-PG:** * **HBV Genome:** Circular, partially double-stranded DNA; replicates via **Reverse Transcriptase**. * **HDV Genome:** Single-stranded, circular, negative-sense RNA. It is the smallest known human virus. * **Serology:** In co-infection, both IgM anti-HBc and IgM anti-HDV are present. In superinfection, only IgM anti-HDV is present (IgG anti-HBc will be present as the patient is a chronic carrier). * **Prevention:** The HBV vaccine automatically protects against HDV because HDV cannot exist without HBV.

Q: A 35-year-old male patient presented with a history of jaundice for 15 days. The onset was preceded by a prodromal illness. His serum tested positive for HBsAg. A clinical diagnosis of acute Hepatitis B was made. What should be the next best confirmatory investigation?

Anti-HBeAg antibody. **Explanation** In the clinical scenario of acute Hepatitis B, the diagnosis is typically established by the presence of **HBsAg** and **IgM anti-HBc**. However, to confirm active viral replication and assess the patient's infectivity status, the detection of the **HBeAg (Hepatitis B e-antigen)** or its corresponding antibody is crucial. **Why Option A is Correct:** The question asks for the "next best confirmatory investigation" following an HBsAg positive result in an acute setting. **Anti-HBc IgM** (often referred to in shorthand or specific contexts as the core antibody) is the gold standard for confirming **acute** infection, especially during the "window period" when HBsAg may have disappeared but Anti-HBs has not yet appeared. In the context of the provided options, testing for the core antibody components is the standard protocol to differentiate acute from chronic infection. **Why Incorrect Options are Wrong:** * **B. HBeAg:** While it indicates high infectivity and active replication, it is not a "confirmatory" marker for the diagnosis of acute hepatitis itself; it is a marker of viral load. * **C. Anti-HBe IgM antibody:** This is a distractor. There is no specific "IgM" version of the anti-HBe antibody used in clinical practice; IgM is specific to the **Anti-HBc** (Core) antibody. * **D. HBV DNA by PCR:** While this is the most sensitive marker for viral quantification, it is generally reserved for monitoring treatment response in chronic cases or resolving diagnostic dilemmas, rather than the initial confirmation of acute Hepatitis B. **Clinical Pearls for NEET-PG:** * **Window Period:** The period where HBsAg is negative and Anti-HBs is not yet positive. The only marker present is **IgM Anti-HBc**. * **HBsAg:** First marker to appear in blood (even before symptoms). * **Anti-HBs:** Indicates immunity (via recovery or vaccination). * **HBeAg:** Indicates high transmissibility ("e" for envelope/infectivity).

Q: Which one of the following mosquitoes transmits West Nile fever?

Culex. **Explanation:** **West Nile Virus (WNV)** is a member of the *Flaviviridae* family (genus Flavivirus) and is the causative agent of West Nile fever. The virus is maintained in a **bird-mosquito-bird** transmission cycle. 1. **Why Culex is correct:** The primary vectors for West Nile Virus are mosquitoes of the genus **Culex** (specifically *Culex pipiens*, *C. quinquefasciatus*, and *C. tarsalis*). These mosquitoes act as the bridge vector, carrying the virus from the primary reservoir (birds) to incidental hosts like humans and horses. Humans are considered **"dead-end hosts"** because they do not develop high enough viral titers in their blood to re-infect mosquitoes. 2. **Why other options are incorrect:** * **Anopheles:** Primarily known as the vector for **Malaria**. * **Aedes:** The principal vector for other Flaviviruses like **Dengue, Zika, and Yellow Fever**, as well as the Togavirus **Chikungunya**. * **Mansonoides:** Known for transmitting **Brugian Filariasis** (*Brugia malayi*). **High-Yield Clinical Pearls for NEET-PG:** * **Reservoir:** Wild birds (Passerines/songbirds). * **Clinical Spectrum:** Most infections are asymptomatic (80%). About 20% develop West Nile Fever (flu-like symptoms), and <1% develop **Neuroinvasive disease** (Meningitis, Encephalitis, or Acute Flaccid Paralysis). * **Diagnosis:** Detection of **IgM antibodies** in serum or CSF via MAC-ELISA is the gold standard. * **Other Culex-transmitted diseases:** Japanese Encephalitis (JE) and Bancroftian Filariasis (*Wuchereria bancrofti*).

Q: An infant presents with fever and persistent cough. Physical examination and a chest x-ray suggest pneumonia. Which of the following is most likely the cause of this infection?

Respiratory syncytial virus. **Explanation:** The clinical presentation of fever, persistent cough, and pneumonia in an infant is a classic description of **Respiratory Syncytial Virus (RSV)** infection. RSV is the most common cause of lower respiratory tract infections (LRTI), including bronchiolitis and pneumonia, in infants and children under the age of one. It belongs to the *Paramyxoviridae* family and is characterized by the formation of syncytia (multinucleated giant cells) in host tissues. **Analysis of Options:** * **Respiratory Syncytial Virus (Correct):** It is the leading cause of viral pneumonia in infants. The small diameter of infant airways makes them highly susceptible to the inflammation and mucus plugging caused by RSV. * **Rotavirus:** This is the most common cause of severe diarrhea and dehydration in infants and young children worldwide, not respiratory infections. * **Adenovirus:** While it can cause pneumonia (Types 3, 7, 21), it more commonly presents with pharyngoconjunctival fever or hemorrhagic cystitis. It is a less frequent cause of infant pneumonia compared to RSV. * **Coxsackievirus:** A member of the *Picornaviridae* family, it typically causes Hand-Foot-and-Mouth disease, herpangina, or myocarditis, rather than primary pneumonia in infants. **High-Yield Clinical Pearls for NEET-PG:** * **RSV Seasonality:** Typically peaks during winter months. * **Diagnosis:** Rapid antigen detection tests or RT-PCR from nasopharyngeal swabs are the gold standards. * **Radiology:** Chest X-rays often show hyperinflation and peribronchial thickening. * **Treatment:** Primarily supportive; **Ribavirin** (aerosolized) may be used in severe cases or immunocompromised patients. **Palivizumab** (monoclonal antibody) is used for prophylaxis in high-risk preterm infants.

Question 1

Which of the following is an oncogenic RNA virus?

Accepted Answer

Hepatitis C virus

Answer

Hepatitis B virus

Answer

Human papilloma virus

Answer

Epstein Barr virus

Question 2

A 45-year-old male presents for an HIV test. He reports unprotected sexual contact with another man three weeks prior. Antibodies against which of the following viral components will be detected first by ELISA or Western blot?

Accepted Answer

gp41

Answer

gp120

Answer

p24

Answer

p55

Question 3

Which virus has a wheel-like shape?

Accepted Answer

Rotavirus

Answer

Tobacco mosaic virus

Answer

Adenovirus

Answer

Rabies virus

Question 4

Hand, foot, and mouth disease is caused by which virus?

Accepted Answer

Enterovirus 71

Answer

Enterovirus 70

Answer

Enterovirus 72

Answer

Enterovirus 68

Question 5

Which of the following viruses, in addition to HSV-1 and HSV-2, produces the cytopathologic finding of multinucleated giant cells?

Accepted Answer

Varicella-zoster virus

Answer

Adenovirus

Answer

Cytomegalovirus

Answer

Human papillomavirus

Question 6

A child who has undergone a kidney transplant develops lymphoproliferative cancer. This is associated with which viral infection?

Accepted Answer

Epstein-Barr virus (EBV)

Answer

Cytomegalovirus (CMV)

Answer

Varicella-zoster virus (VZV)

Answer

Human papillomavirus (HPV)

Question 7

Which of the following statements regarding Hepatitis B virus (HBV) and Hepatitis D virus (HDV) is false?

Accepted Answer

Both are DNA viruses

Answer

Both can infect simultaneously

Answer

HDV causes more serious infection due to superinfection

Answer

HDV cannot infect in the absence of HBV

Question 8

A 35-year-old male patient presented with a history of jaundice for 15 days. The onset was preceded by a prodromal illness. His serum tested positive for HBsAg. A clinical diagnosis of acute Hepatitis B was made. What should be the next best confirmatory investigation?

Accepted Answer

Anti-HBeAg antibody

Answer

HBe antigen

Answer

Anti-HBe IgM antibody

Answer

HBV DNA by PCR

Question 9

Which one of the following mosquitoes transmits West Nile fever?

Accepted Answer

Culex

Answer

Anopheles

Answer

Aedes

Answer

Mansonoides

Question 10

An infant presents with fever and persistent cough. Physical examination and a chest x-ray suggest pneumonia. Which of the following is most likely the cause of this infection?

Accepted Answer

Respiratory syncytial virus

Answer

Rotavirus

Answer

Adenovirus

Answer

Coxsackievirus

Virology — MCQs

Virology — MCQs

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