Virology Practice Questions

Q: What is the term for the virus that causes rabies in humans?

Street virus. **Explanation:** The classification of the Rabies virus into "Street" and "Fixed" strains is a fundamental concept in virology, primarily based on their source and biological behavior. **1. Why "Street Virus" is correct:** The term **Street virus** refers to the rabies virus as it exists in nature, isolated from naturally infected animals (like dogs, bats, or cats) or humans. It is characterized by a long and variable incubation period (usually 1–3 months) and the consistent production of **Negri bodies** (intracytoplasmic inclusion bodies) in the brain tissue. This is the strain responsible for causing clinical rabies in humans. **2. Why the other options are incorrect:** * **Fixed Virus (Option C):** This is a street virus that has been modified by serial passage through the brains of laboratory animals (usually rabbits). This process "fixes" the incubation period to a short, predictable duration (4–6 days). Crucially, fixed viruses are **not** found in nature, do not produce Negri bodies, and are used primarily for vaccine production. * **Wild Virus (Option A):** While "wild" is a general term used for viruses found in nature (like wild-type Polio), it is not the specific technical nomenclature used in Rabies virology to differentiate between natural and laboratory strains. **High-Yield Clinical Pearls for NEET-PG:** * **Negri Bodies:** Pathognomonic for rabies; most commonly found in the **Hippocampus (Ammon’s horn)** and **Cerebellum (Purkinje cells)**. They are absent in infections caused by the Fixed virus. * **Genome:** Negative-sense, single-stranded RNA (ssRNA), bullet-shaped symmetry (Rhabdoviridae). * **Prophylaxis:** Post-exposure prophylaxis (PEP) includes wound cleaning, Rabies vaccine (Active), and Rabies Immunoglobulin (Passive). * **Antigenicity:** Both Street and Fixed viruses share the same surface G-protein antigens, which is why vaccines made from fixed strains protect against street virus exposure.

Q: Giant cell (Hecht's) pneumonia is due to which of the following?

Measles virus. **Explanation:** **Giant cell pneumonia (Hecht’s pneumonia)** is a severe, often fatal interstitial pneumonia caused by the **Measles virus** (Rubeola). It typically occurs in immunocompromised individuals (e.g., those with leukemia, HIV, or severe malnutrition) who fail to develop the characteristic maculopapular rash due to impaired T-cell mediated immunity. 1. **Why Measles is correct:** The hallmark of Measles infection is the formation of **Warthin-Finkeldey giant cells**—large multinucleated cells with eosinophilic intranuclear and intracytoplasmic inclusion bodies. In the lungs, these cells lead to progressive alveolar damage, known as Hecht’s pneumonia. 2. **Why other options are incorrect:** * **CMV:** Causes interstitial pneumonia in transplant recipients, characterized by "Owl’s eye" intranuclear inclusions, but not Hecht’s giant cell pneumonia. * **Malaria:** Can cause Acute Respiratory Distress Syndrome (ARDS) in severe cases (especially *P. falciparum*), but does not produce giant cell pathology. * **Pneumocystis carinii (jirovecii):** Causes PCP pneumonia in HIV patients, characterized by a "crushed ping-pong ball" appearance on silver stain and "foamy" alveolar exudates, not multinucleated giant cells. **High-Yield Clinical Pearls for NEET-PG:** * **Warthin-Finkeldey cells:** Pathognomonic for Measles; found in lymphoid tissue and lungs. * **Koplik’s spots:** Small white spots on buccal mucosa (opposite lower 2nd molars); the earliest clinical sign of Measles. * **Vitamin A:** Supplementation reduces morbidity and mortality in children with Measles. * **SSPE (Subacute Sclerosing Panencephalitis):** A late neurological complication caused by a persistent mutant measles virus.

Q: Which of the following viruses has negative-sense RNA?

Rabies. **Explanation:** The classification of RNA viruses based on their genomic polarity is a high-yield topic for NEET-PG. RNA viruses are categorized as **Positive-sense (+ssRNA)**, which can be directly translated into proteins by host ribosomes, or **Negative-sense (-ssRNA)**, which must first be transcribed into positive-sense mRNA by a viral RNA-dependent RNA polymerase (RdRp). **Correct Answer: A. Rabies** Rabies virus belongs to the **Rhabdoviridae** family. All Rhabdoviruses possess a single-stranded, negative-sense RNA genome. Because the genome cannot be directly translated, the virion must carry its own RdRp enzyme to initiate the infection cycle within the host cell. **Incorrect Options:** * **B. Reovirus:** These are unique because they possess **double-stranded RNA (dsRNA)**. They are the only medically important dsRNA viruses (e.g., Rotavirus). * **C. Coronavirus:** These are **positive-sense (+ssRNA)** viruses. They have the largest genomes among RNA viruses and are enveloped with a helical nucleocapsid. * **D. Calicivirus:** These are **positive-sense (+ssRNA)**, non-enveloped viruses (e.g., Norovirus). **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic for Negative-sense RNA viruses:** "**P**aired **O**ld **B**unny **F**ights **R**eally **A**musing **M**onsters" (**P**aramyxo, **O**rthomyxo, **B**unya, **F**ilo, **R**habdo, **A**rena, **M**yxo). * **Rabies Key Features:** Bullet-shaped morphology, Negri bodies (intracytoplasmic inclusions in Hippocampus/Purkinje cells), and centripetal spread via retrograde axonal transport. * All negative-sense RNA viruses are **enveloped** and carry their own **RNA polymerase**.

Q: Guarnieri's body is seen in which of the following conditions?

Smallpox. **Explanation:** **Guarnieri bodies** are the hallmark histopathological finding in **Smallpox** (Variola virus) and Vaccinia virus infections. These are **intracytoplasmic, eosinophilic inclusion bodies** that represent "viral factories" where DNA replication and assembly occur. Since Poxviruses are unique among DNA viruses because they replicate entirely within the cytoplasm rather than the nucleus, they leave these distinct cytoplasmic imprints. **Analysis of Options:** * **Smallpox (Correct):** Guarnieri bodies are specific to the Poxvirus family. They are found in the epithelial cells of the skin in Smallpox patients. * **Chickenpox (Incorrect):** Caused by the Varicella-Zoster Virus (a Herpesvirus). It produces **Cowdry Type A** inclusion bodies, which are **intranuclear** and eosinophilic, often associated with multinucleated giant cells (Tzanck cells). * **Rubella (Incorrect):** A Togavirus that typically does not produce characteristic diagnostic inclusion bodies like Pox or Herpes viruses. * **Measles (Incorrect):** Caused by a Paramyxovirus. It is characterized by **Warthin-Finkeldey giant cells** and produces both **intracytoplasmic and intranuclear** inclusion bodies (Cowdry type A). **High-Yield NEET-PG Pearls:** * **Poxvirus:** Largest DNA virus; replicates in the **cytoplasm** (exception to the rule). * **Molluscum Contagiosum:** Another Poxvirus that shows **Henderson-Patterson bodies** (large, eosinophilic cytoplasmic inclusions). * **Negri Bodies:** Intracytoplasmic inclusions seen in **Rabies** (Hippocampus/Purkinje cells). * **Owl’s Eye Appearance:** Intranuclear inclusions seen in **CMV**. * **Torres Bodies:** Acidophilic cytoplasmic inclusions seen in **Yellow Fever**.

Q: Which of the following viruses has double-stranded nucleic acid in its genome?

Poxviruses and Reoviruses. ### Explanation The classification of viruses based on their genomic structure is a high-yield topic for NEET-PG. Most DNA viruses are double-stranded (dsDNA), while most RNA viruses are single-stranded (ssRNA). However, there are notable exceptions that are frequently tested. **1. Why Option C is Correct:** * **Poxviruses:** These are the largest and most complex **dsDNA** viruses. Unlike most DNA viruses that replicate in the nucleus, Poxviruses replicate in the cytoplasm because they carry their own DNA-dependent RNA polymerase. * **Reoviruses:** This family (including *Rotavirus*) is the primary exception to the rule for RNA viruses, as they possess a **segmented dsRNA** genome. **2. Why Other Options are Incorrect:** * **Parvoviruses (Options A & B):** These are the smallest DNA viruses and are unique because they have a **ssDNA** genome (the "exception" to the dsDNA rule for DNA viruses). * **Orthomyxoviruses (Options A & D):** This family (including *Influenza*) consists of **ssRNA** viruses with a segmented genome. **3. High-Yield Clinical Pearls for NEET-PG:** * **DNA Exceptions:** All DNA viruses are dsDNA **except Parvoviridae** (ssDNA). All DNA viruses are icosahedral **except Poxviridae** (complex/brick-shaped). * **RNA Exceptions:** All RNA viruses are ssRNA **except Reoviridae** (dsRNA). * **Segmented Genomes:** Remember the mnemonic **BOAR** (Bunyavirus, Orthomyxovirus, Arenavirus, Reovirus). These viruses can undergo genetic reassortment, leading to antigenic shifts. * **Replication Site:** All DNA viruses replicate in the nucleus **except Poxvirus**. All RNA viruses replicate in the cytoplasm **except Influenza and Retroviruses**.

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.

Question 1

Which of the following statements regarding HIV infection is true?

Accepted Answer

Following needle stick injury, infectivity is reduced by the administration of nucleoside analogues.

Answer

CD4 counts are the best predictors of disease progression.

Answer

Infected T cells survive for a month in infected patients.

Answer

In the latent phase, HIV has minimal replication.

Question 2

What is the term for the virus that causes rabies in humans?

Accepted Answer

Street virus

Answer

Wild virus

Answer

Fixed virus

Answer

All of the above

Question 3

Giant cell (Hecht's) pneumonia is due to which of the following?

Accepted Answer

Measles virus

Answer

Cytomegalovirus (CMV)

Answer

Malaria parasite

Answer

Pneumocystis carinii

Question 4

A 23-year-old woman develops vesicular lesions on an erythematous base on her vulvar area. She has tender lymphadenopathy and dysuria. Which of the following is the most likely causative organism?

Accepted Answer

herpes simplex virus type 2 (HSV-2)

Answer

cytomegalovirus (CMV)

Answer

gonococcus

Answer

Treponema pallidum

Question 5

Which of the following viruses has negative-sense RNA?

Accepted Answer

Rabies

Answer

Reovirus

Answer

Coronavirus

Answer

Calicivirus

Question 6

Guarnieri's body is seen in which of the following conditions?

Accepted Answer

Smallpox

Answer

Chickenpox

Answer

Rubella

Answer

Measles

Question 7

Which of the following viruses has double-stranded nucleic acid in its genome?

Accepted Answer

Poxviruses and Reoviruses

Answer

Orthomyxoviruses and Parvoviruses

Answer

Poxviruses and Parvoviruses

Answer

Orthomyxoviruses and Reoviruses

Question 8

Hepatitis B is not transmitted by which of the following?

Accepted Answer

Pasteurised albumin

Answer

Blood transfusion

Answer

Cryoprecipitate

Answer

Sexual contact

Question 9

What is the primary portal of entry for poliovirus?

Accepted Answer

Gastrointestinal tract

Answer

Nasal mucosa

Answer

Lung

Answer

Skin

Question 10

Which body fluid has the maximum HIV load?

Accepted Answer

Blood

Answer

Urine

Answer

Breast milk

Answer

Saliva

Virology — MCQs

Virology — MCQs

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