Virology Practice Questions

Q: Chickenpox is caused by which virus?

Varicella-zoster virus. **Explanation:** **1. Why Varicella-zoster virus (VZV) is correct:** Chickenpox (Varicella) is the primary infection caused by the **Varicella-zoster virus**, which is **Human Herpesvirus 3 (HHV-3)**. It is a highly contagious DNA virus transmitted via respiratory droplets or direct contact with vesicle fluid. After the primary infection resolves, the virus remains **latent in the dorsal root ganglia**. Reactivation later in life results in Herpes Zoster (Shingles). **2. Why the other options are incorrect:** * **Epstein-Barr Virus (EBV/HHV-4):** Causes Infectious Mononucleosis (Glandular fever), Burkitt lymphoma, and Nasopharyngeal carcinoma. It is not associated with vesicular skin rashes like chickenpox. * **Pox virus:** While the name "Chickenpox" suggests a relation, it is a misnomer. Poxviruses (like Variola) cause **Smallpox**. Key differences include: Smallpox lesions are all at the same stage of development, whereas Chickenpox lesions appear in "crops" (pleomorphic). * **Herpes Simplex Virus (HSV-1/HHV-1 & HSV-2/HHV-2):** These cause orolabial herpes (cold sores), genital herpes, and encephalitis, but not the generalized exanthematous rash characteristic of chickenpox. **3. High-Yield Clinical Pearls for NEET-PG:** * **Dew-drop on a rose petal:** Classic description of the varicella vesicle on an erythematous base. * **Centripetal distribution:** The rash appears first on the trunk and spreads to the face and extremities (opposite of Smallpox). * **Tzanck Smear:** Shows **Multinucleated Giant Cells** with Cowdry Type A intranuclear inclusion bodies (seen in VZV and HSV). * **Congenital Varicella Syndrome:** Occurs if the mother is infected in early pregnancy; characterized by limb hypoplasia, cicatricial skin scarring, and microcephaly.

Q: Which of the following diseases is known as the "kissing disease"?

Infectious mononucleosis. **Explanation:** **Infectious Mononucleosis (IM)** is famously known as the "kissing disease" because its primary causative agent, the **Epstein-Barr Virus (EBV)**, is transmitted through oropharyngeal secretions (saliva). It most commonly affects adolescents and young adults. EBV infects B-lymphocytes by binding to the **CD21 receptor** (also known as CR2). **Analysis of Options:** * **Infectious Mononucleosis (Correct):** Characterized by the clinical triad of fever, pharyngitis, and lymphadenopathy (typically posterior cervical). Diagnosis is supported by the presence of **atypical lymphocytes (Downey cells)** on peripheral smear and a positive **Paul-Bunnell (Heterophile antibody) test**. * **AIDS:** Caused by HIV, it is primarily transmitted through sexual contact, blood products, or vertically. While HIV is present in saliva, the concentration is too low for it to be a significant route of transmission compared to IM. * **Primary Syphilis:** Caused by *Treponema pallidum*, it typically presents as a painless chancre at the site of inoculation (usually genitals). While oral chancres occur, it is classified as a classic Sexually Transmitted Infection (STI). * **Recurrent Aphthous Stomatitis:** These are common, non-infectious painful oral ulcers (canker sores). They are not contagious and have an idiopathic or autoimmune etiology rather than a viral one. **High-Yield NEET-PG Pearls:** * **Atypical Lymphocytes:** These are actually activated **CD8+ T-cells** reacting against the infected B-cells. * **Ampicillin Rash:** Patients with IM mistakenly treated with Ampicillin or Amoxicillin often develop a characteristic maculopapular rash. * **Complications:** Splenomegaly is common; patients are advised to avoid contact sports to prevent **splenic rupture**. * **Malignancy Link:** EBV is associated with Burkitt Lymphoma, Nasopharyngeal Carcinoma, and Hodgkin Lymphoma.

Q: Which of the following is NOT a DNA virus?

Paramyxovirus. **Explanation:** The core concept in virology for NEET-PG is distinguishing between DNA and RNA viruses. Most DNA viruses are double-stranded (except Parvovirus) and replicate in the nucleus (except Poxvirus). **Why Paramyxovirus is the correct answer:** Paramyxovirus is a **single-stranded, negative-sense RNA virus**. This family includes clinically significant pathogens such as Measles, Mumps, Parainfluenza, and Respiratory Syncytial Virus (RSV). Unlike DNA viruses, these replicate in the cytoplasm using their own RNA-dependent RNA polymerase. **Analysis of incorrect options (DNA Viruses):** * **Adenovirus:** A non-enveloped, double-stranded DNA (dsDNA) virus known for causing pharyngoconjunctival fever, hemorrhagic cystitis, and gastroenteritis (serotypes 40/41). * **Poxvirus:** The largest and most complex dsDNA virus. It is a high-yield exception because it **replicates in the cytoplasm** (guarded by Guarnieri bodies) despite being a DNA virus. * **Parvovirus (B19):** A unique DNA virus because it is **single-stranded (ssDNA)**. It causes Erythema Infectiosum (Fifth disease) and aplastic crisis in patients with sickle cell anemia. **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic for DNA Viruses:** "**HHAPPPPy**" (Hepadna, Herpes, Adeno, Pox, Parvo, Papilloma, Polyoma). * **The Exceptions Rule:** All DNA viruses are dsDNA except **Parvo** (ssDNA). All DNA viruses are icosahedral except **Pox** (complex/brick-shaped). All DNA viruses replicate in the nucleus except **Pox**. * **Paramyxovirus Hallmark:** They all possess a **Fusion (F) protein**, which leads to the formation of multinucleated giant cells (syncytia). Palivizumab is a monoclonal antibody used against the F protein in RSV.

Q: Which of the following is true regarding Kyasanur Forest Disease (KFD)?

It is a zoonosis.. **Explanation:** **Kyasanur Forest Disease (KFD)**, popularly known as "Monkey Fever," is a viral hemorrhagic fever endemic to South India (primarily Karnataka). 1. **Why Option A is correct:** KFD is a classic **zoonosis**. It is caused by the Kyasanur Forest Disease Virus (KFDV), a member of the family *Flaviviridae*. The virus circulates in nature between ticks (the vector) and wild animals like rodents and shrews (the reservoir). Humans are "accidental hosts" and represent a dead-end for the virus, as there is no human-to-human transmission. 2. **Why Option B is incorrect:** While the question asks for the *most* true statement regarding its nature, Option B is technically a partial truth but less definitive than its zoonotic classification. KFD does not just "affect" monkeys; monkeys (Langurs and Bonnet macaques) act as **sentinel animals**. Their sudden death in the forest is often the first sign of an impending outbreak in humans. 3. **Why Options C and D are incorrect:** KFD is caused by a **virus** (Flavivirus), not bacteria or Rickettsia. **High-Yield Clinical Pearls for NEET-PG:** * **Vector:** Primarily the hard tick, ***Haemaphysalis spinigera***. * **Transmission:** Through the bite of an infected tick or contact with an infected animal (especially a sick/dead monkey). * **Clinical Features:** Biphasic illness—initial high fever, headache, and severe myalgia, followed by a hemorrhagic phase (epistaxis, GI bleed) or neurological symptoms in some cases. * **Diagnosis:** PCR (early phase) or IgM ELISA. * **Prevention:** A **formalin-inactivated vaccine** is used in endemic areas of Karnataka.

Q: All of the following are examples of intracytoplasmic inclusion bodies except?

Owl's eye bodies. **Explanation:** In virology, inclusion bodies are distinct structures formed in the nucleus or cytoplasm of host cells during viral replication. They serve as "viral factories" or sites of capsid assembly. **Why Option D is correct:** **Owl’s eye bodies** are the characteristic **intranuclear** inclusion bodies seen in **Cytomegalovirus (CMV)** infections. They are large, eosinophilic inclusions surrounded by a clear halo, extending to the nuclear membrane. Because they are located within the nucleus, they are not intracytoplasmic. (Note: "Owl's eye" appearance is also used to describe Reed-Sternberg cells in Hodgkin Lymphoma, but in virology, it specifically refers to CMV). **Why the other options are incorrect:** * **A. Molluscum bodies (Henderson-Patterson bodies):** Large, eosinophilic **intracytoplasmic** inclusions found in the epidermis in *Molluscum contagiosum* (Poxvirus). * **B. Guarneri bodies:** Eosinophilic **intracytoplasmic** inclusions diagnostic of **Variola (Smallpox)** or Vaccinia virus. * **C. Bollinger bodies:** Large **intracytoplasmic** inclusions seen in **Fowlpox**. These contain smaller internal structures known as Borrel bodies. **High-Yield Clinical Pearls for NEET-PG:** * **Poxviruses** are the only DNA viruses that replicate in the cytoplasm; hence, they produce **intracytoplasmic** inclusions. * **Negri bodies** (intracytoplasmic) are pathognomonic for **Rabies** (found in Hippocampus/Purkinje cells). * **Cowdry Type A** (intranuclear) are seen in **Herpes Simplex Virus (HSV)** and Varicella-Zoster Virus (VZV). * **Torres bodies** (intranuclear) are seen in **Yellow Fever**. * **Measles** is unique as it can produce **both** intranuclear and intracytoplasmic inclusions (Warthin-Finkeldey cells).

Q: HIV binds to macrophages having which of the following molecules?

CD4 and CCR5 molecule. **Explanation:** The entry of HIV into host cells is a multi-step process requiring both a primary receptor and a co-receptor. 1. **Why Option C is correct:** HIV primarily infects cells expressing the **CD4 molecule** (the primary receptor). However, binding to CD4 alone is insufficient for viral entry. The virus must also bind to a chemokine co-receptor. **Macrophages** (and memory T-cells) predominantly express the **CCR5** co-receptor. Strains of HIV that utilize CCR5 are termed **M-tropic (Macrophage-tropic)** or R5 strains. These are typically responsible for the initial infection and horizontal transmission. 2. **Why other options are incorrect:** * **Option A:** While CD4 is necessary, it is not the only molecule required; a co-receptor is mandatory for membrane fusion. * **Option B:** **CXCR4** is the co-receptor found primarily on **naive T-helper cells**. Strains using CXCR4 are termed **T-tropic** or X4 strains and usually appear in the later stages of HIV infection, associated with a rapid decline in CD4 counts. * **Option D:** These are both co-receptors; without the primary **CD4** docking site, the virus cannot initiate the attachment process. **High-Yield Clinical Pearls for NEET-PG:** * **gp120:** The viral envelope protein that binds to the CD4 receptor. * **gp41:** The viral protein responsible for fusion with the host cell membrane. * **Maraviroc:** A CCR5 antagonist (entry inhibitor) used in HIV treatment; it is only effective against R5-tropic virus. * **CCR5-Δ32 Mutation:** A genetic mutation (32-base pair deletion) that provides homozygous individuals with significant resistance to HIV infection.

Q: A 30-year-old patient presented with a 10-day history of jaundice. Liver function tests showed a bilirubin of 10 mg/dl, SGOT/SGPT of 1100/1450, and serum alkaline phosphatase of 240 IU. The patient was positive for HBsAg. What is the confirmatory test to establish an acute Hepatitis B infection?

IgM anti-HBc antibody. ### Explanation **1. Why IgM anti-HBc is the Correct Answer:** In clinical practice, the presence of **HBsAg** (Hepatitis B surface antigen) indicates that the patient is currently infected with HBV, but it cannot distinguish between an **acute infection** and a **chronic carrier state** (where HBsAg persists for >6 months). The **IgM anti-HBc (Hepatitis B core antibody)** is the definitive marker for **acute infection**. It appears shortly after HBsAg and remains positive for approximately 4–6 months. Crucially, it is the only marker present during the **"Window Period"** (the gap between the disappearance of HBsAg and the appearance of Anti-HBs), making it the gold standard for diagnosing acute HBV. **2. Why the Other Options are Incorrect:** * **HBeAg (Option B):** This is a marker of **active viral replication** and high infectivity. While often present in acute phases, it can also be seen in chronic "wild-type" infections; thus, it is not specific for an acute diagnosis. * **HBV DNA by PCR (Option C):** This is the most sensitive marker for quantifying **viral load** and monitoring treatment response. However, it does not differentiate between acute and chronic phases. * **Anti-HBc antibody (Option D):** This refers to **Total Anti-HBc** (IgM + IgG). Since IgG anti-HBc persists for life, a "Total" test cannot differentiate a new infection from a past or chronic one. **3. NEET-PG High-Yield Pearls:** * **Window Period Marker:** IgM anti-HBc. * **Marker of Recovery/Immunity:** Anti-HBs (Hepatitis B surface antibody). * **Chronic Infection:** Defined by the persistence of HBsAg for **>6 months**. * **Post-Vaccination Profile:** Only Anti-HBs is positive (HBsAg and Anti-HBc are negative). * **Rule of Thumb:** If HBsAg (+) and IgM anti-HBc (+), it is **Acute**. If HBsAg (+) and IgM anti-HBc (–) but IgG anti-HBc (+), it is **Chronic**.

Q: A viral organism was isolated from a painful blister on the lip of a teenage girl. The agent was found to have double-stranded, linear DNA and was enveloped. The patient had a similar sore approximately 2 months ago. Which of the following is the most likely causative organism?

Herpes simplex type 1 virus. ### Explanation **Correct Answer: C. Herpes simplex type 1 virus (HSV-1)** The clinical presentation of a painful blister on the lip (herpes labialis) in a teenager, combined with a history of recurrence, is classic for **Herpes simplex virus type 1 (HSV-1)**. * **Virology:** HSV-1 is a member of the *Herpesviridae* family, characterized by a **double-stranded, linear DNA** genome and a lipid **envelope** derived from the host nuclear membrane. * **Pathogenesis:** After the primary infection, the virus remains **latent** in the sensory nerve ganglia (specifically the **trigeminal ganglion** for oral lesions). Periodic reactivation leads to recurrent sores, often triggered by stress, sunlight, or fever. **Incorrect Options:** * **A. Adenovirus:** While it has dsDNA, it is **non-enveloped**. It typically causes pharyngoconjunctival fever or keratoconjunctivitis, not recurrent vesicular lip sores. * **B. Coxsackie virus:** Part of the *Picornaviridae* family, it has a **ssRNA** genome and is **non-enveloped**. It causes Herpangina or Hand-Foot-Mouth disease, which present as ulcers but do not typically recur in the same site. * **D. Herpes zoster virus (VZV):** Although it is an enveloped dsDNA virus, it typically presents as a **dermatomal** rash (shingles) in older or immunocompromised individuals. Recurrence twice within two months in a teenager is highly atypical for VZV. **High-Yield Clinical Pearls for NEET-PG:** * **Tzanck Smear:** Look for **multinucleated giant cells** and **Cowdry Type A** intranuclear inclusion bodies. * **Latency Site:** HSV-1 (Trigeminal ganglion); HSV-2 (Sacral ganglion); VZV (Dorsal root ganglion). * **Drug of Choice:** Acyclovir (inhibits viral DNA polymerase). * **Enveloping:** Herpesviruses are unique because they acquire their envelope by budding through the **inner nuclear membrane**.

Q: Attachment of Ebstein Barr virus in nasopharynx is mediated through which receptor?

CD 21. **Explanation:** The correct answer is **CD 21**. **1. Why CD 21 is correct:** Epstein-Barr Virus (EBV), a member of the *Herpesviridae* family (HHV-4), primarily targets B-lymphocytes and epithelial cells of the nasopharynx. The viral envelope glycoprotein **gp350/220** binds specifically to the **CD21** molecule (also known as Complement Receptor 2 or CR2) found on the surface of these cells. This binding is the critical first step for viral entry and subsequent infection. **2. Why the other options are incorrect:** * **CD 4:** This is the primary receptor for **HIV** (Human Immunodeficiency Virus). It is found on T-helper cells, macrophages, and dendritic cells. * **CD 3:** This is a pan-T-cell marker associated with the T-cell receptor (TCR) complex. It is involved in signal transduction but does not serve as a receptor for EBV. * **CD 8:** This is a marker for cytotoxic T-cells. While EBV infection triggers a massive proliferation of CD8+ T-cells (seen as **atypical lymphocytes** or Downey cells on a blood smear), the virus does not use CD8 as an entry receptor. **3. High-Yield Clinical Pearls for NEET-PG:** * **Atypical Lymphocytes:** The characteristic "Downey cells" seen in Infectious Mononucleosis are actually activated T-cells (CD8+) reacting against the EBV-infected B-cells. * **Associated Malignancies:** EBV is strongly linked to Burkitt Lymphoma (t(8;14)), Nasopharyngeal Carcinoma, and Hodgkin Lymphoma. * **Diagnosis:** The **Monospot Test** detects heterophile antibodies (IgM) that agglutinate sheep or horse RBCs. * **Mnemonic:** "EBV loves B-cells via CD21" (2 x 1 = 2, and B is the 2nd letter of the alphabet).

Question 1

Chickenpox is caused by which virus?

Accepted Answer

Varicella-zoster virus

Answer

Epstein-barr virus

Answer

Pox virus

Answer

Herpes simplex virus

Question 2

Which of the following diseases is known as the "kissing disease"?

Accepted Answer

Infectious mononucleosis

Answer

Acquired immunodeficiency syndrome (AIDS)

Answer

Primary syphilis

Answer

Recurrent aphthous stomatitis

Question 3

Which of the following is NOT a DNA virus?

Accepted Answer

Paramyxovirus

Answer

Adenovirus

Answer

Poxvirus

Answer

Parvovirus

Question 4

Which of the following is true regarding Kyasanur Forest Disease (KFD)?

Accepted Answer

It is a zoonosis.

Answer

It affects monkeys.

Answer

It is caused by bacteria.

Answer

It is caused by Rickettsia.

Question 5

All of the following are examples of intracytoplasmic inclusion bodies except?

Accepted Answer

Owl's eye bodies

Answer

Molluscum bodies

Answer

Guarneri bodies

Answer

Bollinger bodies

Question 6

HIV binds to macrophages having which of the following molecules?

Accepted Answer

CD4 and CCR5 molecule

Answer

CD4 molecule

Answer

CD4 and CXCR molecules

Answer

CXCR and CCR5 molecules

Question 7

What is true about prions?

Accepted Answer

Heat labile

Answer

Associated with Cruetzfeldt-Jacob disease

Answer

Sensitive to proteases

Answer

Infectious proteinaceous particles

Question 8

A 30-year-old patient presented with a 10-day history of jaundice. Liver function tests showed a bilirubin of 10 mg/dl, SGOT/SGPT of 1100/1450, and serum alkaline phosphatase of 240 IU. The patient was positive for HBsAg. What is the confirmatory test to establish an acute Hepatitis B infection?

Accepted Answer

IgM anti-HBc antibody

Answer

HBeAg

Answer

HBV DNA by PCR

Answer

Anti-HBc antibody

Question 9

A viral organism was isolated from a painful blister on the lip of a teenage girl. The agent was found to have double-stranded, linear DNA and was enveloped. The patient had a similar sore approximately 2 months ago. Which of the following is the most likely causative organism?

Accepted Answer

Herpes simplex type 1 virus

Answer

Adenovirus

Answer

Coxsackie virus

Answer

Herpes zoster virus

Question 10

Attachment of Ebstein Barr virus in nasopharynx is mediated through which receptor?

Accepted Answer

CD 21

Answer

CD 4

Answer

CD 3

Answer

CD 8

Virology — MCQs

Virology — MCQs

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