Virology Practice Questions

Q: Which of the following is a Group B (flaviviruses) Arbovirus?

Dengue fever. ### Explanation **Correct Answer: A. Dengue fever** **Concept:** Arboviruses (Arthropod-borne viruses) were historically classified into groups based on antigenic relationships before modern molecular taxonomy. * **Group A:** Corresponds to the **Alphavirus** genus (Family: *Togaviridae*). * **Group B:** Corresponds to the **Flavivirus** genus (Family: *Flaviviridae*). **Dengue fever** is a classic member of the **Flavivirus** genus (Group B). It is transmitted by the *Aedes aegypti* mosquito and exists in four serotypes (DEN 1-4). **Analysis of Incorrect Options:** * **B. Rift Valley fever:** This belongs to the **Phlebovirus** genus within the *Phenuiviridae* family (formerly *Bunyaviridae*). It is not classified under Group A or B. * **C. Chikungunya fever:** This is an **Alphavirus** (Family: *Togaviridae*), making it a **Group A** arbovirus. * **D. Japanese encephalitis (JE):** While JE is indeed a **Flavivirus** (Group B), in the context of standard medical examinations, if both Dengue and JE are present, Dengue is often the prototypical answer for Group B. However, technically, JE is also a Group B arbovirus. *Note: In many competitive exams, Dengue is the preferred "textbook" representative for this classification.* **High-Yield Clinical Pearls for NEET-PG:** * **Group A (Alphaviruses):** Chikungunya, Eastern Equine Encephalitis (EEE), Western Equine Encephalitis (WEE). * **Group B (Flaviviruses):** Dengue, Yellow Fever, Japanese Encephalitis, West Nile Virus, Kyasanur Forest Disease (KFD), and Zika Virus. * **Vector Shortcut:** *Aedes* mosquitoes transmit Dengue, Chikungunya, and Yellow Fever. *Culex* mosquitoes transmit Japanese Encephalitis and West Nile Virus. * **Diagnostic Gold Standard:** IgM ELISA (MAC-ELISA) is commonly used for Dengue and JE diagnosis. For Dengue, NS1 antigen is the marker of choice in the early febrile phase (Days 1–5).

Q: Which congenital infection has minimal teratogenic risk to the fetus?

HIV. **Explanation:** The core concept in this question is the distinction between **teratogenicity** (structural malformations) and **vertical transmission** (infection of the fetus). **Correct Option: A. HIV** While HIV has a high rate of vertical transmission (if untreated), it is **not considered a teratogen**. HIV does not interfere with organogenesis; therefore, it does not cause structural birth defects or a specific "congenital syndrome." The primary risk to the infant is the development of pediatric AIDS later in life, rather than physical malformations at birth. **Incorrect Options:** * **B. Rubella:** A classic teratogen. Infection during the first trimester leads to **Congenital Rubella Syndrome (CRS)**, characterized by the triad of cataracts, sensorineural deafness, and cardiac defects (PDA). * **C. Varicella:** Maternal infection (especially between 8–20 weeks) can cause **Congenital Varicella Syndrome**, resulting in limb hypoplasia, cicatricial skin scarring, and microcephaly. * **D. CMV:** The most common intrauterine infection. It is a potent teratogen causing periventricular calcifications, microcephaly, and sensorineural hearing loss. **NEET-PG High-Yield Pearls:** * **Most common congenital infection:** CMV. * **Highest teratogenic risk period:** First trimester (organogenesis). * **HIV Management:** To minimize vertical transmission, HAART is given to the mother, and elective C-section is preferred if the viral load is >1000 copies/mL. Zidovudine is typically given to the neonate. * **Parvovirus B19:** Not typically structural but causes **Hydrops Fetalis** due to severe fetal anemia.

Q: Which of the following is true about Rabies virus?

Rabies is diagnosed by immunofluorescence.. **Explanation:** **Correct Option (A):** Direct Fluorescent Antibody (DFA) test is the **gold standard** for diagnosing rabies. It involves detecting rabies virus antigens in brain tissue (post-mortem) or skin biopsies from the nape of the neck (ante-mortem). Immunofluorescence is highly sensitive and specific because it utilizes fluorescently labeled antibodies that bind specifically to the rabies nucleoprotein. **Incorrect Options:** * **B:** Rabies does not cause lifelong immunity because the disease is **100% fatal** once clinical symptoms appear. There are no "survivors" to develop natural immunity. * **C:** While there are different lineages, the Rabies virus (Lyssavirus genus) is **serologically monotypic**. This means there is only one major serotype, which is why a single vaccine provides protection against all strains globally. * **D:** Modern rabies vaccines (like PCEV or HDCV) are **inactivated (killed)** vaccines. Live attenuated vaccines are used for wildlife (oral baits) but are never used in humans due to safety concerns. **High-Yield Clinical Pearls for NEET-PG:** * **Negri Bodies:** Pathognomonic intracytoplasmic eosinophilic inclusions found in the hippocampus (Ammon’s horn) and cerebellum (Purkinje cells). * **Incubation Period:** Typically 1–3 months; it is shorter if the bite is closer to the CNS (e.g., face). * **Post-Exposure Prophylaxis (PEP):** Includes wound washing, Rabies Vaccine (Days 0, 3, 7, 14, 28), and Rabies Immunoglobulin (RIG) for Category III bites. * **Street Virus vs. Fixed Virus:** "Street virus" is the wild-type; "Fixed virus" is the laboratory strain used for vaccine production.

Q: All of the following statements about the Ebola virus are true EXCEPT?

The incubation period is 2 to 12 weeks.. **Explanation:** The correct answer is **B** because the statement regarding the incubation period is incorrect. The incubation period for Ebola Virus Disease (EVD) is typically **2 to 21 days** (average 8–10 days), not 2 to 12 weeks. Patients are not infectious until they develop symptoms. **Analysis of Options:** * **Option A:** Ebola virus, along with Marburg virus, belongs to the **Filoviridae** family. These are enveloped, non-segmented, negative-sense RNA viruses characterized by their unique filamentous or "thread-like" appearance under electron microscopy. * **Option C:** Transmission occurs via **direct contact** with infected blood, secretions, organs, or other bodily fluids of infected people, or with surfaces contaminated with these fluids. It is not an airborne infection. * **Option D:** EVD is a systemic illness. In severe cases, multi-organ failure occurs, most notably **renal and liver impairment**, often accompanied by internal and external bleeding (hemorrhagic manifestations). **High-Yield Clinical Pearls for NEET-PG:** * **Natural Reservoir:** Fruit bats of the *Pteropodidae* family are considered the natural hosts. * **Diagnosis:** Real-time PCR (RT-PCR) is the preferred diagnostic test during the acute phase. * **Pathogenesis:** The virus targets endothelial cells, mononuclear phagocytes, and hepatocytes. * **Key Feature:** It causes a "cytokine storm," leading to increased vascular permeability and shock. * **Vaccine:** The **rVSV-ZEBOV** vaccine (Ervebo) is a live-attenuated recombinant vaccine used for prevention.

Q: Which of the following is true of Rotavirus?

Most common cause of diarrheal disease in infants. **Explanation:** **Rotavirus** is a member of the *Reoviridae* family and is the leading cause of severe, dehydrating diarrhea in infants and young children (typically 6 months to 2 years of age) worldwide. 1. **Why Option C is Correct:** Rotavirus is the **most common cause of infantile gastroenteritis**. It infects the mature enterocytes of the small intestine, leading to malabsorption and osmotic diarrhea. The presence of the viral protein **NSP4**, which acts as an enterotoxin, further induces secretory diarrhea by increasing intracellular calcium. 2. **Why Other Options are Incorrect:** * **Option A:** Rotaviruses are notoriously **difficult to grow** in standard cell cultures. They require the addition of proteolytic enzymes like trypsin to the medium for successful replication. * **Option B:** Rotavirus is a **double-stranded RNA (dsRNA)** virus, not DNA. It is characterized by a unique **segmented genome (11 segments)** and a wheel-like appearance under electron microscopy (hence the name "Rota"). * **Option D:** Infections are most severe in children. Adults are rarely affected or have mild symptoms due to pre-existing immunity. The peak age of infection is **6–24 months**. **High-Yield NEET-PG Pearls:** * **Morphology:** Non-enveloped, icosahedral, triple-layered protein capsid (Wheel-like/Cartwheel appearance). * **Transmission:** Fecal-oral route. * **Diagnosis:** Antigen detection in stool via **ELISA** or Latex Agglutination is the gold standard. * **Vaccines:** Live attenuated oral vaccines are available (e.g., **Rotarix** - monovalent; **RotaTeq** - pentavalent; **Rotavac** - indigenous Indian vaccine). * **Seasonality:** More common in winter months ("Winter Diarrhea").

Q: What is the most common agent responsible for Bronchiolitis?

RSV (Respiratory Syncytial Virus). **Explanation:** **1. Why RSV is the correct answer:** Respiratory Syncytial Virus (RSV) is the single most common cause of bronchiolitis worldwide, accounting for approximately **50–80% of all cases**. It primarily affects infants and children under two years of age, with a peak incidence between 2 to 6 months. The virus causes inflammation, edema, and necrosis of the epithelial cells lining the small airways (bronchioles), leading to the classic clinical presentation of wheezing, tachypnea, and chest retractions. **2. Why the other options are incorrect:** * **Adenovirus:** While it can cause severe bronchiolitis and "Bronchiolitis Obliterans" (a chronic obstructive lung disease), it is a much less frequent cause than RSV. It more commonly presents as pharyngoconjunctival fever. * **Herpesvirus:** These viruses (like HSV or CMV) typically cause systemic infections or pneumonia in immunocompromised hosts but are not standard causative agents for acute bronchiolitis in infants. * **Influenza virus:** Although it causes significant respiratory morbidity and can lead to viral pneumonia, it is a less common cause of isolated bronchiolitis compared to RSV and Parainfluenza. **3. Clinical Pearls for NEET-PG:** * **Seasonality:** RSV outbreaks typically occur in **winter and early spring**. * **Diagnosis:** Primarily clinical; however, **Rapid Antigen Detection Tests (RADT)** or PCR from nasopharyngeal swabs are used for confirmation. * **Microscopy:** Look for **multinucleated giant cells (syncytia)** formed by the fusion of infected cells (due to the viral F-protein). * **Treatment:** Mainly supportive (oxygen, hydration). **Ribavirin** (nebulized) is reserved for severe cases or high-risk infants. * **Prophylaxis:** **Palivizumab** (a monoclonal antibody against the F-protein) is used for high-risk preterm infants.

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).

Question 1

Which of the following statements regarding HIV transmission from mother to fetus is FALSE?

Accepted Answer

The most common mode of transmission is during breastfeeding, accounting for approximately 15-30% of cases.

Answer

Vertical transmission is more common in preterm infants.

Answer

Cesarean and vaginal deliveries have an equal chance of transmitting the virus.

Answer

Breastfeeding is not absolutely contraindicated in developing countries.

Question 2

Which of the following is a Group B (flaviviruses) Arbovirus?

Accepted Answer

Dengue fever

Answer

Rift Valley fever

Answer

Chikungunya fever

Answer

Japanese encephalitis

Question 3

Which congenital infection has minimal teratogenic risk to the fetus?

Accepted Answer

HIV

Answer

Rubella

Answer

Varicella

Answer

CMV

Question 4

Which of the following is true about Rabies virus?

Accepted Answer

Rabies is diagnosed by immunofluorescence.

Answer

Rabies causes lifelong immunity.

Answer

Rabies has various strains of viruses.

Answer

Rabies vaccine is always live attenuated.

Question 5

All of the following statements about the Ebola virus are true EXCEPT?

Accepted Answer

The incubation period is 2 to 12 weeks.

Answer

It is a member of the Filoviridae family.

Answer

It is transmitted by direct contact.

Answer

In severe cases, it can lead to renal and liver impairment.

Question 6

Which of the following is true of Rotavirus?

Accepted Answer

Most common cause of diarrheal disease in infants

Answer

Easily grown in cell culture

Answer

Double-stranded DNA virus

Answer

Adults and old people account for 60% of infections

Question 7

What is the most common agent responsible for Bronchiolitis?

Accepted Answer

RSV (Respiratory Syncytial Virus)

Answer

Adenovirus

Answer

Herpesvirus

Answer

Influenza virus

Question 8

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 9

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 10

Which virus has a wheel-like shape?

Accepted Answer

Rotavirus

Answer

Tobacco mosaic virus

Answer

Adenovirus

Answer

Rabies virus

Virology — MCQs

Virology — MCQs

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