Virology Practice Questions

Q: Hepatitis B is not transmitted by which of the following?

Pasteurised albumin. **Explanation:** Hepatitis B Virus (HBV) is a blood-borne pathogen primarily transmitted through parenteral routes, sexual contact, and vertical transmission (mother-to-child). **Why Pasteurised Albumin is the Correct Answer:** Human albumin solutions undergo a rigorous stabilization and sterilization process. During manufacturing, albumin is subjected to **pasteurization** (heating at **60°C for 10 hours**). This specific temperature and duration are sufficient to inactivate heat-labile viruses, including HBV, HCV, and HIV. Therefore, pasteurized albumin is considered safe and does not transmit Hepatitis B. **Analysis of Incorrect Options:** * **Blood Transfusion:** Whole blood and its components (RBCs, Platelets) are classic vehicles for HBV transmission if the donor is in the "window period" or has occult HBV infection. * **Cryoprecipitate:** This is a fraction of plasma rich in Factor VIII, von Willebrand factor, and fibrinogen. Since it is prepared by thawing fresh frozen plasma and is **not** subjected to heat inactivation or viral filtration like albumin, it carries a risk of transmitting HBV. * **Sexual Contact:** HBV is found in high concentrations in semen and vaginal secretions. It is significantly more infectious (approx. 50–100 times) than HIV via sexual routes. **High-Yield Clinical Pearls for NEET-PG:** * **HBsAg** is the first serological marker to appear after infection. * **HBV DNA** is the most sensitive indicator of viral replication. * **Heat Stability:** HBV is relatively heat-stable but is inactivated by autoclaving (121°C) and pasteurization (60°C for 10 hours). * **Risk of Transmission:** The risk of HBV transmission after a needle-stick injury from an HBeAg-positive source is approximately **30%** (compared to 3% for HCV and 0.3% for HIV).

Q: What is the primary portal of entry for poliovirus?

Gastrointestinal tract. ### Explanation **Correct Option: A. Gastrointestinal tract** Poliovirus is a member of the **Picornaviridae** family (genus *Enterovirus*). The primary mode of transmission is the **fecal-oral route**. Upon ingestion, the virus survives the acidic environment of the stomach and enters the body through the gastrointestinal tract. It initially multiplies in the lymphoid tissues of the pharynx (tonsils) and the **Peyer’s patches** of the ileum. From here, it spreads to the regional lymph nodes and enters the bloodstream (primary viremia). **Analysis of Incorrect Options:** * **B. Nasal mucosa:** While some respiratory transmission can occur via oropharyngeal secretions in the very early stages of infection, it is not the primary portal of entry. * **C. Lung:** Poliovirus does not cause primary respiratory infections or enter via the lower respiratory tract. * **D. Skin:** Poliovirus cannot penetrate intact skin. Unlike viruses like Rabies or Hepatitis B, it is not transmitted through bites or percutaneous injury. **High-Yield Clinical Pearls for NEET-PG:** * **Site of Replication:** The virus primarily replicates in the **motor neurons of the anterior horn cells** of the spinal cord, leading to flaccid paralysis. * **Specimen of Choice:** For diagnosis, **stool samples** are superior to throat swabs because viral shedding in feces persists for several weeks. * **Vaccine Differences:** * **Sabin (OPV):** Live attenuated; induces local **IgA immunity** in the gut (blocks transmission). * **Salk (IPV):** Killed/Inactivated; induces humoral **IgG immunity** (prevents paralysis but not gut infection). * **Most Common Outcome:** In >90% of cases, polio infection is **asymptomatic** or a minor flu-like illness (Abortive Polio).

Q: Which body fluid has the maximum HIV load?

Blood. **Explanation:** The concentration of HIV (viral load) varies significantly across different body fluids, which directly determines the risk of transmission. **1. Why Blood is the Correct Answer:** Blood contains the highest concentration of HIV virions. This is because HIV primarily infects and replicates within CD4+ T-lymphocytes and macrophages, which are abundant in the bloodstream. Consequently, percutaneous exposure to infected blood (e.g., needle-stick injuries or blood transfusions) carries the highest risk of transmission compared to other body fluids. **2. Analysis of Incorrect Options:** * **Breast Milk:** While breast milk contains enough virus to facilitate mother-to-child transmission (MTCT), the viral concentration is significantly lower than that found in blood or semen. * **Urine & Saliva:** These are considered "non-infectious" fluids in the context of HIV (unless visibly contaminated with blood). They contain negligible amounts of the virus or possess inhibitory enzymes (like secretory leukocyte protease inhibitor in saliva) that neutralize the virus, making transmission via these routes virtually impossible. **3. High-Yield Clinical Pearls for NEET-PG:** * **Hierarchy of Viral Load:** Blood > Semen > Vaginal Secretions > Breast Milk. * **Transmission Risk:** The highest risk of transmission per single act is through **Blood Transfusion** (approx. 90-95%), followed by Receptive Anal Intercourse. * **Window Period:** The time between infection and the appearance of detectable antibodies (usually 2-8 weeks). The **p24 antigen** is the earliest marker detectable in the blood after the eclipse phase. * **Post-Exposure Prophylaxis (PEP):** Should ideally be started within 2 hours, but no later than 72 hours, and continued for 28 days.

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.

Question 1

Hepatitis B is not transmitted by which of the following?

Accepted Answer

Pasteurised albumin

Answer

Blood transfusion

Answer

Cryoprecipitate

Answer

Sexual contact

Question 2

What is the primary portal of entry for poliovirus?

Accepted Answer

Gastrointestinal tract

Answer

Nasal mucosa

Answer

Lung

Answer

Skin

Question 3

Which body fluid has the maximum HIV load?

Accepted Answer

Blood

Answer

Urine

Answer

Breast milk

Answer

Saliva

Question 4

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 5

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 6

Which congenital infection has minimal teratogenic risk to the fetus?

Accepted Answer

HIV

Answer

Rubella

Answer

Varicella

Answer

CMV

Question 7

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 8

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 9

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 10

What is the most common agent responsible for Bronchiolitis?

Accepted Answer

RSV (Respiratory Syncytial Virus)

Answer

Adenovirus

Answer

Herpesvirus

Answer

Influenza virus

Virology — MCQs

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