Virology Practice Questions

Q: A 3-year-old child presents with coryza, conjunctivitis, low-grade fever, and Koplik's spots. The causative agent of this disease belongs to which group of viruses?

Morbillivirus. ### Explanation **1. Why the Correct Answer is Right:** The clinical presentation of **coryza, conjunctivitis, fever, and Koplik’s spots** is pathognomonic for **Measles (Rubeola)**. Koplik’s spots (small white spots on the buccal mucosa opposite the lower molars) are the hallmark pre-eruptive sign. The Measles virus belongs to the family *Paramyxoviridae* and specifically to the genus **Morbillivirus**. It is a pleomorphic, enveloped virus with a single-stranded, negative-sense RNA genome. **2. Why the Other Options are Incorrect:** * **Paramyxovirus (Option A):** While Measles belongs to the *Paramyxoviridae* family, "Paramyxovirus" is a broad family name (and formerly a genus name now split). In NEET-PG, when a specific genus like *Morbillivirus* is provided, it is the more precise and correct answer. * **Rubulavirus (Option C):** This genus includes the **Mumps virus** and Parainfluenza viruses 2 and 4. Mumps typically presents with parotitis, not Koplik’s spots or a maculopapular rash. * **Pneumovirus (Option D):** This genus (now often classified under the family *Pneumoviridae*) includes **Respiratory Syncytial Virus (RSV)**, which is a leading cause of bronchiolitis and pneumonia in infants, lacking the systemic rash and oral signs of Measles. **3. High-Yield Clinical Pearls for NEET-PG:** * **Sequence of Symptoms:** Fever → 3 C’s (Cough, Coryza, Conjunctivitis) → Koplik’s spots → Exanthem (starts behind ears). * **Vitamin A:** Supplementation reduces morbidity and mortality in Measles. * **Complications:** The most common complication is **Otitis Media**; the most common cause of death is **Pneumonia** (Hecht’s giant cell pneumonia); the most dreaded late complication is **SSPE** (Subacute Sclerosing Panencephalitis). * **Warthin-Finkeldey Cells:** Multinucleated giant cells found in lymphoid tissue, characteristic of Measles.

Q: Which virus causes a mononucleosis-like syndrome caused by a latent herpesvirus, is often a congenital infection, and is frequently diagnosed by detecting large amounts of virus excreted in urine?

Cytomegalovirus. **Explanation:** The correct answer is **Cytomegalovirus (CMV)**. This question highlights three classic clinical pillars of CMV infection: 1. **Mononucleosis-like Syndrome:** CMV is the most common cause of heterophile-antibody negative (Monospot negative) mononucleosis. While it presents similarly to EBV (fever, lymphadenopathy, atypical lymphocytosis), pharyngitis and splenomegaly are typically less severe. 2. **Congenital Infection:** CMV is the most common intrauterine infection worldwide. It presents with the classic triad of periventricular calcifications, microcephaly, and sensorineural hearing loss. 3. **Viral Shedding:** CMV establishes lifelong latency in mononuclear cells (monocytes). During primary infection or reactivation, the virus is excreted in high titers in the **urine (viruria)** and saliva, making urine culture or PCR a primary diagnostic tool, especially in neonates. **Analysis of Incorrect Options:** * **A. Epstein-Barr virus (EBV):** While it causes classic infectious mononucleosis, it is **Heterophile positive** and is not a major cause of congenital infections or diagnosed via urine excretion. * **C. HHV-6:** This virus causes **Roseola Infantum** (Exanthem Subitum), characterized by high fever followed by a rash. It does not typically cause a mononucleosis syndrome or significant congenital disease. * **D. Parvovirus B19:** A single-stranded DNA virus (not a herpesvirus) that causes Erythema Infectiosum (Fifth disease) and hydrops fetalis, but not a mononucleosis-like syndrome. **NEET-PG High-Yield Pearls:** * **Histology:** Look for "Owl’s eye" intranuclear inclusion bodies. * **Site of Latency:** Monocytes, Macrophages, and Lymphocytes. * **Treatment:** Ganciclovir is the drug of choice (Valganciclovir for oral maintenance). * **Transplant Medicine:** CMV is the most common viral infection complicating solid organ transplants.

Q: All of the following statements about parvovirus B19 are true except?

It crosses the placenta in less than 10% of cases.. **Explanation:** Parvovirus B19 is a clinically significant pathogen in the NEET-PG curriculum, known for its specific tropism for erythroid progenitor cells. **1. Why Option B is the correct answer (The "Except" statement):** While Parvovirus B19 is a well-known cause of vertical transmission, the statement that it crosses the placenta in less than 10% of cases is incorrect. In reality, if a non-immune pregnant woman is infected, the virus crosses the placenta in approximately **30% to 50%** of cases. While most fetuses are unaffected, infection can lead to **Hydrops Fetalis** (due to severe fetal anemia and high-output heart failure) or fetal death, particularly during the second trimester. **2. Analysis of Incorrect Options:** * **Option A (DNA Virus):** This is true. Parvovirus B19 is unique as it is the only **Single-Stranded DNA (ssDNA)** virus that causes disease in humans. It is also non-enveloped and icosahedral. * **Option C & D (Severe Anemia/Aplastic Crisis):** These are true. The virus binds to the **P-antigen** (globoside) on erythroblasts, leading to cell lysis. In patients with high red cell turnover (e.g., Sickle Cell Anemia, Hereditary Spherocytosis), this causes a life-threatening **Transient Aplastic Crisis**. In immunocompromised patients, it can lead to pure red cell aplasia and chronic anemia. **High-Yield Clinical Pearls for NEET-PG:** * **Erythema Infectiosum (Fifth Disease):** Characterized by the classic **"Slapped Cheek"** rash in children. * **Arthropathy:** More common in adults, presenting as symmetrical small joint arthritis (mimicking Rheumatoid Arthritis). * **Diagnosis:** Detection of **IgM antibodies** or PCR for viral DNA. * **Receptor:** P-antigen (Globoside) is the essential cellular receptor.

Q: Congenital rubella syndrome is most prominent in an infant when a pregnant woman becomes infected during which period?

The first trimester of pregnancy. **Explanation:** The risk of fetal damage in **Congenital Rubella Syndrome (CRS)** is inversely proportional to the gestational age at the time of maternal infection. [1] **1. Why the First Trimester is Correct:** The first trimester (specifically the first 8–12 weeks) is the period of **organogenesis**. During this window, the Rubella virus can cross the placenta and cause chronic fetal infection, leading to cell death and inhibition of mitosis. If infection occurs within the first 8 weeks, the risk of congenital malformations is as high as **85%**. After the 16th week, the risk of major structural defects drops significantly as organs are already formed. **2. Why Other Options are Incorrect:** * **Options B, C, and D:** Infections occurring in the late second or third trimester (including the weeks or hours before delivery) rarely result in the classic triad of CRS. While late-term infection can lead to fetal infection, it usually results in a subclinical infection or a "blueberry muffin" rash at birth, rather than permanent structural defects like cataracts or heart disease. [1] **3. High-Yield Clinical Pearls for NEET-PG:** * **Gregg’s Triad:** The classic presentation of CRS includes **Cataracts** (most common eye finding), **Sensorineural Deafness** (most common overall finding), and **Congenital Heart Disease** (most commonly Patent Ductus Andreas/PDA). * **Diagnosis:** Detection of **Rubella-specific IgM** in the neonate’s cord blood or persistent IgG levels beyond 6 months is diagnostic. * **Vaccination:** Rubella is a **Live Attenuated Vaccine** (RA 27/3 strain). It is strictly contraindicated during pregnancy, and pregnancy should be avoided for 1 month (4 weeks) after vaccination. * **Blueberry Muffin Rash:** This represents extramedullary hematopoiesis and is a characteristic skin finding in CRS.

Q: Which type of sample can be used to isolate poliovirus earliest?

Stool. **Explanation:** Poliovirus is an enterovirus transmitted primarily via the fecal-oral route. Understanding its pathogenesis is key to identifying the correct diagnostic sample. **Why Stool is Correct:** After ingestion, the virus multiplies in the lymphoid tissues of the pharynx and the Peyer’s patches of the small intestine. It is excreted in the **stool** for several weeks, starting as early as **2–5 days after infection** (often before the onset of paralysis). Because the viral load is highest and persists longest in the gastrointestinal tract, stool is the most reliable and earliest sample for isolation. **Analysis of Incorrect Options:** * **Throat Swab:** While the virus can be isolated from the throat during the first week of illness, it disappears rapidly (usually within 7 days), making it less reliable than stool. * **Blood:** Viremia occurs early in the "minor illness" phase (pre-paralytic). However, it is transient and usually subsides by the time clinical symptoms of meningitis or paralysis appear, making it difficult to capture. * **Cerebrospinal Fluid (CSF):** Paradoxically, poliovirus is **rarely isolated from CSF**, even in patients with paralytic polio. Diagnosis of CNS involvement is usually clinical or via PCR, but not primary isolation from CSF. **High-Yield Clinical Pearls for NEET-PG:** * **Gold Standard:** Virus isolation from stool (two samples collected 24 hours apart). * **Culture:** Poliovirus is typically grown on Monkey Kidney or human cell lines (e.g., HeLa, HEp-2), showing characteristic **cytopathic effects (CPE)** like cell rounding and pyknosis. * **Specimen Transport:** Stool samples should be sent at **4°C** (Reverse Cold Chain) to maintain viral viability. * **Key Fact:** Polio is a positive-sense, single-stranded RNA virus belonging to the *Picornaviridae* family.

Q: Suckling mice are used in the isolation of which virus?

Arbovirus. **Explanation:** The use of **suckling mice** (mice less than 48 hours old) is a classic method for the isolation of **Arboviruses** (e.g., Dengue, Japanese Encephalitis) and certain **Coxsackieviruses**. These viruses are often difficult to grow in standard cell lines or embryonated eggs. Suckling mice are preferred because they lack a mature immune system and possess specific undifferentiated tissues that are highly susceptible to viral replication. For Arboviruses, the specimen is typically inoculated **intracerebrally**, leading to encephalitis, paralysis, or death, which confirms viral presence. **Analysis of Incorrect Options:** * **Herpes virus (B):** These are typically isolated using **cell cultures** (e.g., Human embryonic lung fibroblasts) where they produce characteristic Cowdry Type A intranuclear inclusion bodies. * **Pox virus (C):** The gold standard for isolation is the **Chorioallantoic Membrane (CAM)** of embryonated hen’s eggs, where they produce visible "pocks." * **HIV (D):** As a retrovirus, HIV is isolated using **co-culture of patient’s PBMCs** (Peripheral Blood Mononuclear Cells) with stimulated healthy T-lymphocytes. Diagnosis is primarily via ELISA, Western Blot, or p24 antigen detection. **High-Yield Clinical Pearls for NEET-PG:** * **Suckling mice** are also the specific medium to differentiate **Coxsackie A** (diffuse myositis/flaccid paralysis) from **Coxsackie B** (focal myositis/spastic paralysis). * **Intracerebral inoculation** in mice is the most sensitive method for isolating the **Rabies virus** (though Negri bodies in brain tissue is the classic histological finding). * Modern virology has largely replaced animal inoculation with **Cell Culture**, but suckling mice remain the "gold standard" for primary isolation of unknown Arboviruses in many reference labs.

Q: All of the following are examples of enveloped viruses EXCEPT:

Adenovirus. **Explanation:** The classification of viruses into **enveloped** and **non-enveloped (naked)** is a high-yield concept in NEET-PG Microbiology. Enveloped viruses derive their outer lipid bilayer from host cell membranes, making them more susceptible to heat, detergents, and lipid solvents (like alcohol). **1. Why Adenovirus is the Correct Answer:** Adenovirus is a **non-enveloped (naked) DNA virus**. It possesses a characteristic icosahedral capsid with "penton fibers" (spikes) projecting from the vertices. Because it lacks a lipid envelope, it is relatively stable in the environment and can survive the acidic conditions of the GI tract, which is why it can cause both respiratory infections and gastroenteritis. **2. Analysis of Incorrect Options:** * **Coronavirus:** An enveloped, positive-sense single-stranded RNA virus. Its envelope is derived from the endoplasmic reticulum-Golgi intermediate compartment (ERGIC). * **Molluscum Contagiosum Virus:** A member of the **Poxviridae** family. Poxviruses are unique, complex-shaped DNA viruses that possess an envelope, though they do not acquire it by budding from the plasma membrane. * **Herpes Virus:** A large, enveloped DNA virus. It acquires its envelope by budding through the **inner nuclear membrane** of the host cell. **Clinical Pearls for NEET-PG:** * **Mnemonic for Naked DNA Viruses:** "**P**apova, **A**deno, **P**arvo" (**PAP**). (Note: Parvovirus is the only one that is single-stranded). * **Mnemonic for Naked RNA Viruses:** "**P**icorna, **R**eo, **C**alici, **H**epe" (**P**e**RCH**). * **High-Yield Fact:** All DNA viruses are double-stranded except Parvovirus; all are icosahedral except Poxvirus; and all replicate in the nucleus except Poxvirus.

Q: Oral hairy leukoplakia is associated with which virus?

Epstein-Barr virus. **Explanation:** **Oral Hairy Leukoplakia (OHL)** is a clinical condition characterized by white, corrugated (hairy), non-scrapable patches typically found on the lateral margins of the tongue. **1. Why Epstein-Barr Virus (EBV) is correct:** OHL is caused by the **opportunistic replication of EBV (Human Herpesvirus 4)** in the squamous epithelium of the tongue. It occurs almost exclusively in immunocompromised individuals, particularly those with HIV/AIDS. Unlike oral candidiasis, these lesions **cannot be scraped off**. The diagnosis is confirmed by detecting EBV DNA or proteins within the epithelial cells. **2. Why the other options are incorrect:** * **Cytomegalovirus (CMV):** While CMV causes opportunistic infections in HIV patients (like retinitis or esophagitis), it does not cause leukoplakia. * **Human Immunodeficiency Virus (HIV):** While OHL is a classic clinical marker for HIV progression and low CD4 counts, HIV itself is the underlying cause of immunosuppression, not the direct viral cause of the leukoplakia. * **Human Papillomavirus (HPV):** HPV is associated with oral warts (verruca vulgaris) and oropharyngeal cancers, but not with the "hairy" white patches of OHL. **Clinical Pearls for NEET-PG:** * **Diagnostic Marker:** OHL is often the first clinical sign of HIV infection or a signal that a patient’s CD4 count has dropped below **200 cells/mm³**. * **Histology:** Look for **Koilocytes** (ballooning cells) in the upper layers of the epithelium and "Cowdry type A" inclusions. * **Treatment:** Usually not required unless for cosmetic reasons; however, it often resolves with **Highly Active Antiretroviral Therapy (HAART)** as the immune system recovers. * **Differential Diagnosis:** Must be distinguished from **Oral Candidiasis** (which scrapes off) and **Leukoplakia** (a premalignant lesion associated with tobacco). OHL is **not** premalignant.

Question 1

Epstein-Barr virus (EBV) VCA-IgG 1:80 and EBV antibody to early antigen EA1:320 suggest which one of the following diseases?

Accepted Answer

Chronic infectious mononucleosis

Answer

Primary syphilis

Answer

Scarlet fever

Answer

Primary atypical pneumonia

Question 2

A 3-year-old child presents with coryza, conjunctivitis, low-grade fever, and Koplik's spots. The causative agent of this disease belongs to which group of viruses?

Accepted Answer

Morbillivirus

Answer

Paramyxovirus

Answer

Rubulavirus

Answer

Pneumovirus

Question 3

Which virus causes a mononucleosis-like syndrome caused by a latent herpesvirus, is often a congenital infection, and is frequently diagnosed by detecting large amounts of virus excreted in urine?

Accepted Answer

Cytomegalovirus

Answer

Epstein-Barr virus

Answer

HHV-6

Answer

Parvovirus

Question 4

All of the following statements about parvovirus B19 are true except?

Accepted Answer

It crosses the placenta in less than 10% of cases.

Answer

It is a DNA virus.

Answer

It can cause severe anemia.

Answer

It can cause aplastic crisis.

Question 5

Congenital rubella syndrome is most prominent in an infant when a pregnant woman becomes infected during which period?

Accepted Answer

The first trimester of pregnancy

Answer

One week before a full-term delivery

Answer

One month before a full-term delivery

Answer

Hours before childbirth

Question 6

All of the following infections may be transmitted via blood transfusion, except?

Accepted Answer

Dengue virus

Answer

Parvovirus B-19

Answer

Cytomegalovirus

Answer

Hepatitis G virus

Question 7

Which type of sample can be used to isolate poliovirus earliest?

Accepted Answer

Stool

Answer

Blood

Answer

Throat swab

Answer

Cerebrospinal fluid

Question 8

Suckling mice are used in the isolation of which virus?

Accepted Answer

Arbovirus

Answer

Herpes virus

Answer

Pox virus

Answer

HIV

Question 9

All of the following are examples of enveloped viruses EXCEPT:

Accepted Answer

Adenovirus

Answer

Coronavirus

Answer

Molluscum contagiosum virus

Answer

Herpes virus

Question 10

Oral hairy leukoplakia is associated with which virus?

Accepted Answer

Epstein-Barr virus

Answer

Cytomegalovirus

Answer

Human immunodeficiency virus

Answer

Human papillomavirus

Virology — MCQs

Virology — MCQs

On this page

Practice by Chapter

Want unlimited practice?