Virology Practice Questions

Q: All of the following are markers of active replication of chronic hepatitis B, except:

AST & ALT. **Explanation:** The core concept in Hepatitis B (HBV) serology is distinguishing between **viral replication markers** and **biochemical markers of liver injury**. **Why AST & ALT is the correct answer:** AST (Aspartate Aminotransferase) and ALT (Alanine Aminotransferase) are intracellular enzymes released into the bloodstream when hepatocytes are damaged. While elevated levels indicate **active liver inflammation or necrosis** (hepatitis), they do not directly measure the virus's ability to replicate. In chronic HBV, a patient can have high viral replication with normal transaminases (Immune Tolerant phase) or low replication with high transaminases (due to other causes like superinfection or alcohol). **Why the other options are markers of active replication:** * **HBV DNA (Option A):** This is the most sensitive and direct quantitative marker of viral load and active replication. * **HBV DNA Polymerase (Option B):** This enzyme is required for the synthesis of viral DNA; its presence in the serum directly correlates with active viral assembly. * **HBeAg (Option C):** The 'e' antigen is a secretory product of the nucleocapsid gene. Its presence is a classic qualitative marker indicating high infectivity and active viral replication. **High-Yield Clinical Pearls for NEET-PG:** * **Window Period:** The time between the disappearance of HBsAg and the appearance of Anti-HBs. The only marker present is **Anti-HBc IgM**. * **Best marker of infectivity:** HBV DNA (Quantitative) > HBeAg (Qualitative). * **First marker to appear:** HBsAg. * **Pre-core Mutants:** These patients are HBeAg negative but still have high HBV DNA levels and active liver disease. * **Ground Glass Hepatocytes:** Histological hallmark of chronic HBV infection.

Q: Which Human Papillomavirus (HPV) type is most commonly implicated in genital (vulval) warts?

HPV 6. **Explanation:** The correct answer is **HPV 6**. Genital warts, also known as **Condyloma acuminata**, are benign epithelial proliferations caused by "low-risk" types of Human Papillomavirus. **HPV 6 and 11** are responsible for approximately 90% of all genital wart cases. These types have a low potential for malignant transformation but are highly contagious and associated with significant morbidity. **Analysis of Options:** * **HPV 6 (Correct):** This is the most common type associated with genital warts. It targets the squamous epithelium of the vulva, vagina, and perianal region. * **HPV 16 & 18 (Incorrect):** These are "high-risk" oncogenic types. HPV 16 is the most common cause of **Cervical Cancer** (squamous cell carcinoma) and Vulvar Intraepithelial Neoplasia (VIN). HPV 18 is strongly associated with cervical **adenocarcinoma**. * **HPV 31 (Incorrect):** This is another high-risk type associated with cervical dysplasia and cancer, but it is less common than types 16 and 18 and rarely causes benign warts. **High-Yield Clinical Pearls for NEET-PG:** * **Low-risk HPV (6, 11):** Associated with Condyloma acuminata and Recurrent Respiratory Papillomatosis (RRP). * **High-risk HPV (16, 18, 31, 33, 45):** Associated with Cervical, Vaginal, Vulvar, Anal, and Oropharyngeal cancers. * **Histology:** The hallmark of HPV infection is **Koilocytosis** (cells with perinuclear halos and wrinkled "raisinoid" nuclei). * **Vaccination:** The Quadrivalent (Gardasil) and Nonavalent vaccines protect against types 6 and 11, thereby preventing genital warts.

Q: Which of the following statements about Hepatitis B virus (HBV) is false?

It has the least chance of chronicity.. **Explanation:** **Why Option D is the correct (false) statement:** Hepatitis B Virus (HBV) does **not** have the least chance of chronicity; in fact, it has a significant risk of becoming chronic, especially when acquired early in life. The risk of chronicity is inversely proportional to age: approximately **90% in neonates** (vertical transmission), 30% in children, and **5–10% in immunocompetent adults**. Among viral hepatitides, Hepatitis C (HCV) has the highest overall rate of chronicity (~75–85%), while Hepatitis A and E do not cause chronic infection at all (except HEV in transplant recipients). **Analysis of incorrect options:** * **Option A (True):** HBV is a member of the *Hepadnaviridae* family. It is a partially double-stranded **DNA virus** that replicates via reverse transcription. * **Option B (True):** HBV is primarily transmitted through parenteral routes (**blood transfusions**, contaminated needles), sexual contact, and vertical transmission (mother-to-child). * **Option C (True):** **HBsAg** (Surface Antigen) is the first serological marker to appear in the blood and is the hallmark of active infection (both acute and chronic). **High-Yield Clinical Pearls for NEET-PG:** * **Window Period:** The time when HBsAg and Anti-HBs are both negative; **Anti-HBc IgM** is the only marker of acute infection during this phase. * **Infectivity Marker:** **HBeAg** indicates high viral replication and high infectivity. * **Ground Glass Hepatocytes:** Characteristic histopathological finding in chronic HBV infection due to HBsAg accumulation in the endoplasmic reticulum. * **Dane Particle:** The complete, infectious 42nm virion of HBV.

Q: Which of the following is a common clinical manifestation of human parvovirus B19 infection?

Erythema infectiosum. **Explanation:** **Parvovirus B19** is a small, non-enveloped DNA virus that specifically targets and replicates in **erythroid progenitor cells** (via the P antigen). **1. Why Erythema Infectiosum is the correct answer:** Also known as **Fifth Disease**, this is the **most common** clinical manifestation of Parvovirus B19, primarily seen in children. It is characterized by a classic "slapped-cheek" rash on the face, followed by a reticular, lace-like maculopapular rash on the trunk and extremities. The rash is immune-mediated and typically appears after the viremic phase has resolved. **2. Analysis of Incorrect Options:** * **A. Aplastic crisis:** While Parvovirus B19 causes this, it occurs specifically in patients with high red cell turnover (e.g., Sickle Cell Anemia, Hereditary Spherocytosis). It is a severe complication, not the most "common" manifestation in the general population. * **B. Anemia in the neonatal period:** Parvovirus infection during pregnancy can lead to fetal loss or hydrops, but it is not a standard cause of neonatal anemia. * **D. Hydrops fetalis:** This occurs if a non-immune pregnant woman is infected, leading to severe fetal anemia and high-output cardiac failure. While high-yield, it occurs in less than 10% of maternal infections. **Clinical Pearls for NEET-PG:** * **Receptor:** P antigen (Globoside) on RBCs. * **Adults:** Often present with **symmetrical arthralgia/arthritis** (mimicking Rheumatoid Arthritis). * **Immunocompromised:** Can cause **Pure Red Cell Aplasia (PRCA)** and chronic anemia. * **Diagnosis:** Detection of IgM antibodies or PCR (especially in aplastic crisis where antibody response may be delayed).

Q: During the first week of infection, Dengue virus can be best detected by which method?

NS1 antigen detection. **Explanation:** The laboratory diagnosis of Dengue virus infection depends on the timing of the clinical presentation. During the **first week (Days 1–5)** of illness, the patient is in the viremic phase. **1. Why NS1 Antigen Detection is correct:** The **NS1 (Non-Structural Protein 1)** is a highly conserved glycoprotein secreted by Dengue-infected cells. It reaches high concentrations in the serum during the early febrile phase (Day 1 to Day 9). Because it appears before antibodies are detectable, it is the **gold standard for early diagnosis** (alongside RT-PCR). It is highly specific and can be detected even before the fever subsides. **2. Why the other options are incorrect:** * **MAC-ELISA (IgM Antibody Capture ELISA):** This detects IgM antibodies. IgM typically appears only after **Day 5–7** of the illness. Testing for IgM during the first week often yields a false negative because the immune system has not yet produced a measurable antibody response. * **ICT (Immunochromatographic Test) for IgM:** Similar to ELISA, this rapid test detects antibodies. While faster, it lacks the sensitivity of ELISA and is still dependent on the patient being in the late acute or convalescent phase (after the first week). **3. High-Yield Clinical Pearls for NEET-PG:** * **Best Diagnostic Sequence:** * **Days 1–5:** NS1 Antigen or RT-PCR (RT-PCR is the most sensitive but NS1 is more widely used). * **After Day 5:** IgM MAC-ELISA. * **Secondary Infection:** In secondary dengue, IgG levels rise rapidly (anamnesis), while IgM may be low or undetectable. * **Vector:** *Aedes aegypti* (Day biter). * **Hallmark Lab Finding:** Thrombocytopenia (low platelet count) and hemoconcentration (rising hematocrit).

Q: Which virus is known to cause a latent infection?

Hepatitis B virus (HBV). **Explanation:** **Hepatitis B Virus (HBV)** is the correct answer because it establishes latency through the formation of **cccDNA (covalently closed circular DNA)** in the nucleus of infected hepatocytes. This episomal form persists indefinitely, acting as a template for viral transcription even when the patient is clinically asymptomatic or under antiviral therapy. Reactivation can occur during periods of immunosuppression (e.g., chemotherapy or HIV co-infection). **Analysis of Incorrect Options:** * **Rubella:** This is an enveloped RNA virus (Togaviridae) that causes an acute self-limiting infection (German measles). While it can cause persistent infection in the fetus (Congenital Rubella Syndrome), it does not undergo a true latent phase in the general population. * **Pertussis:** This is caused by the bacterium *Bordetella pertussis*, not a virus. It causes an acute respiratory infection (Whooping cough) and does not exhibit latency. * **Rotavirus:** A Reovirus that causes acute gastroenteritis, primarily in children. It is a non-enveloped RNA virus that is shed in feces during the acute phase but does not establish a latent reservoir in the body. **High-Yield Clinical Pearls for NEET-PG:** * **Latency vs. Persistence:** Latency involves the maintenance of the viral genome without active replication (e.g., HBV, HSV, VZV, EBV). * **HBV Markers:** The disappearance of HBsAg and the appearance of Anti-HBs signify recovery; however, cccDNA may still persist in the liver. * **Other Latent Viruses:** Always remember the "Big Three" families: **Herpesviridae** (all members), **Retroviridae** (HIV), and **Hepadnaviridae** (HBV). * **Reactivation Risk:** Before starting biologicals (like Rituximab), patients must be screened for latent HBV to prevent fulminant hepatic failure.

Q: A patient presents with keratoconjunctivitis. The differential diagnosis should include infection with which of the following viruses?

Adenovirus. **Explanation:** **Adenovirus** is the most common viral cause of **epidemic keratoconjunctivitis (EKC)**, typically associated with serotypes 8, 19, and 37. The virus has a predilection for mucous membranes, including the conjunctiva and respiratory tract. EKC is characterized by sudden onset of watery discharge, pain, and "foreign body sensation," often followed by subepithelial corneal infiltrates which can impair vision. Adenoviruses also cause **Pharyngoconjunctival Fever** (triad of fever, pharyngitis, and conjunctivitis), usually linked to serotypes 3 and 7. **Analysis of Incorrect Options:** * **Parvovirus (B19):** Primarily causes Erythema Infectiosum (Fifth disease) in children, characterized by a "slapped-cheek" rash, and aplastic crisis in patients with chronic hemolytic anemias. It does not typically involve the cornea. * **Epstein-Barr virus (EBV):** The causative agent of Infectious Mononucleosis. While it can cause mild conjunctivitis or eyelid edema (Hoagland sign), it is not a classic cause of keratoconjunctivitis. * **Respiratory Syncytial Virus (RSV):** A major cause of bronchiolitis and pneumonia in infants. Its pathology is localized to the lower respiratory tract; ocular involvement is not a standard clinical feature. **High-Yield Clinical Pearls for NEET-PG:** * **Shipyard Eye:** A historical name for Adenoviral EKC due to industrial outbreaks. * **Transmission:** Highly contagious; spread via respiratory droplets, contaminated fingers, or ophthalmic instruments (tonometers). * **Other Viral Causes:** Herpes Simplex Virus (HSV) is another major cause of keratoconjunctivitis, typically presenting with characteristic **dendritic ulcers** on fluorescein staining. * **Structure:** Adenovirus is a non-enveloped, dsDNA virus with fiber spikes projecting from the penton bases, which are essential for attachment.

Q: Which of the following virus families exhibits the property of elution?

Myxovirus. **Explanation:** **1. Why Myxovirus is correct:** The property of **elution** is a hallmark of the **Orthomyxoviridae** (Influenza) and **Paramyxoviridae** families (collectively known as Myxoviruses). These viruses possess two specific surface spikes: **Hemagglutinin (HA)** and **Neuraminidase (NA)**. * **Hemagglutination:** The HA spikes bind to sialic acid receptors on Red Blood Cells (RBCs), causing them to clump. * **Elution:** After binding, the enzyme **Neuraminidase** cleaves the sialic acid receptors, releasing the virus from the RBC surface. This spontaneous release of the virus from the agglutinated RBCs is termed "elution." **2. Why other options are incorrect:** * **Togavirus & Adenovirus:** While some viruses in these families (like Rubella or certain Adenovirus serotypes) can cause hemagglutination, they **lack the Neuraminidase enzyme**. Therefore, once they bind to RBCs, they do not spontaneously elute. * **Parvovirus:** Specifically B19, binds to the P-antigen on erythroid progenitor cells. It causes hemagglutination but lacks the enzymatic machinery for elution. **Clinical Pearls for NEET-PG:** * **H-N Spikes:** In Influenza, HA is for **attachment/entry**, while NA is for **release/elution**. * **Antiviral Link:** Oseltamivir and Zanamivir are **Neuraminidase inhibitors**; they work by preventing elution, thereby trapping the virus within the host cell or on the cell surface. * **Receptor:** The specific receptor for Myxoviruses is **N-acetylneuraminic acid (Sialic acid)**. * **Diagnostic Test:** The Hemagglutination Inhibition (HAI) test is used to detect antibodies against these viruses.

Question 1

All of the following are markers of active replication of chronic hepatitis B, except:

Accepted Answer

AST & ALT

Answer

HBV DNA

Answer

HBV DNA Polymerase

Answer

HBeAg

Question 2

Which Human Papillomavirus (HPV) type is most commonly implicated in genital (vulval) warts?

Accepted Answer

HPV 6

Answer

HPV 16

Answer

HPV 18

Answer

HPV 31

Question 3

Which of the following statements about Hepatitis B virus (HBV) is false?

Accepted Answer

It has the least chance of chronicity.

Answer

It is a DNA virus.

Answer

It spreads by blood transfusions.

Answer

HBsAg is a marker of infection.

Question 4

Which of the following is a common clinical manifestation of human parvovirus B19 infection?

Accepted Answer

Erythema infectiosum

Answer

Aplastic crisis in hemolytic anemia patients

Answer

Anemia in the neonatal period

Answer

Hydrops fetalis

Question 5

During the first week of infection, Dengue virus can be best detected by which method?

Accepted Answer

NS1 antigen detection

Answer

MACELISA

Answer

ICT test to detect IgM

Answer

None of the above

Question 6

Which virus is known to cause a latent infection?

Accepted Answer

Hepatitis B virus (HBV)

Answer

Rubella

Answer

Pertussis

Answer

Rotavirus

Question 7

Which of the following statements regarding respiratory viruses is FALSE?

Accepted Answer

Mumps virus can cause aseptic meningitis, not typically septic meningitis, in adults.

Answer

RSV is the most common cause of bronchiolitis in infants.

Answer

Measles virus can cause subacute sclerosing panencephalitis (SSPE).

Answer

Epstein-Barr virus (EBV) can be associated with pleuritis.

Question 8

A patient presents with keratoconjunctivitis. The differential diagnosis should include infection with which of the following viruses?

Accepted Answer

Adenovirus

Answer

Parvovirus

Answer

Epstein-Barr virus

Answer

Respiratory syncytial virus

Question 9

Which of the following virus families exhibits the property of elution?

Accepted Answer

Myxovirus

Answer

Togavirus

Answer

Parvovirus

Answer

Adenovirus

Question 10

Viruses can be isolated from clinical samples by cultivation in all of the following except:

Accepted Answer

Chemically defined media

Answer

Tissue culture

Answer

Embryonated eggs

Answer

Animals

Virology — MCQs

Virology — MCQs

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