Virology Practice Questions

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.

Q: Which virus is responsible for microcephaly, intracerebral calcifications, and hepatosplenomegaly when the fetus is exposed in utero?

Cytomegalovirus. **Explanation:** The clinical triad of **microcephaly, intracerebral calcifications, and hepatosplenomegaly** is the classic presentation of **Congenital Cytomegalovirus (CMV) infection**, the most common intrauterine infection worldwide. 1. **Why Cytomegalovirus is correct:** CMV has a predilection for the central nervous system and the reticuloendothelial system. A key diagnostic feature is the pattern of intracranial calcifications, which are characteristically **periventricular** (around the ventricles). Other features include sensorineural hearing loss (the most common non-genetic cause), chorioretinitis, and a "blueberry muffin" rash (extramedullary hematopoiesis). 2. **Why other options are incorrect:** * **Rubella:** While it causes microcephaly and hepatosplenomegaly, its classic triad is **Cataracts, Sensorineural deafness, and Congenital Heart Disease** (PDA or Pulmonary artery stenosis). * **Varicella Zoster:** Congenital Varicella Syndrome is characterized by **cicatricial skin scarring**, limb hypoplasia, and rudimentary digits, rather than isolated calcifications. * **Rubeola (Measles):** This is not a classic TORCH infection and does not typically cause this constellation of congenital malformations. **High-Yield Pearls for NEET-PG:** * **CMV:** Most common cause of sensorineural hearing loss in neonates. Look for **"Owl’s eye"** intranuclear inclusion bodies on histology. * **Calcification Patterns:** CMV = Periventricular; Toxoplasmosis = Diffuse/Scattered. * **Treatment:** Ganciclovir or Valganciclovir is used to reduce the severity of hearing loss and developmental delays. * **Diagnosis:** Best confirmed by PCR of saliva or urine within the first 3 weeks of life.

Q: Parvovirus B19 usually causes a very mild disease. Two groups of people for whom it can be serious, however, are?

Pregnant women and sickle-cell anemics. **Explanation:** Parvovirus B19 is a small, non-enveloped DNA virus that specifically targets and replicates in **erythroid progenitor cells** (precursors of red blood cells) by binding to the **P-antigen**. While it causes the mild "Slapped Cheek" rash (Erythema Infectiosum) in healthy children, it is life-threatening for two specific groups: 1. **Sickle-cell Anemics (and other chronic hemolytic anemias):** Because Parvovirus B19 temporarily halts erythropoiesis (red cell production), patients who already have a shortened RBC lifespan cannot compensate for the drop. This leads to a life-threatening **Aplastic Crisis**, characterized by a sudden drop in hemoglobin and a low reticulocyte count. 2. **Pregnant Women:** The virus can cross the placenta and infect the fetal bone marrow. This leads to severe fetal anemia, high-output cardiac failure, and generalized edema, a condition known as **Hydrops Fetalis**, which can result in intrauterine fetal death. **Analysis of Incorrect Options:** * **Option A:** While teenagers can get the virus (often presenting with arthralgia), it is rarely "serious" compared to the risks in pregnancy or anemia. * **Option C & D:** Parvovirus B19 is transmitted via respiratory droplets, not primarily through sexual contact or IV drug use. While asplenics are at risk for encapsulated bacteria, their risk with Parvovirus is not as specific as those with high RBC turnover (sickle cell). **High-Yield Clinical Pearls for NEET-PG:** * **Receptor:** P-antigen (Globoside) on RBCs. * **Diagnosis:** Low reticulocyte count is the hallmark of an aplastic crisis. * **Pure Red Cell Aplasia:** Can occur in immunocompromised patients (e.g., HIV) due to chronic Parvovirus infection. * **Arthropathy:** Common in adult females, mimicking Rheumatoid Arthritis.

Question 1

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 2

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 3

Which virus is known to cause a latent infection?

Accepted Answer

Hepatitis B virus (HBV)

Answer

Rubella

Answer

Pertussis

Answer

Rotavirus

Question 4

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 5

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 6

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

Accepted Answer

Myxovirus

Answer

Togavirus

Answer

Parvovirus

Answer

Adenovirus

Question 7

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

Question 8

Which virus is responsible for microcephaly, intracerebral calcifications, and hepatosplenomegaly when the fetus is exposed in utero?

Accepted Answer

Cytomegalovirus

Answer

Rubella

Answer

Varicella zoster

Answer

Rubeola

Question 9

Parvovirus B19 usually causes a very mild disease. Two groups of people for whom it can be serious, however, are?

Accepted Answer

Pregnant women and sickle-cell anemics

Answer

Teenagers and pregnant women

Answer

The sexually promiscuous and drug addicts

Answer

Alcoholics and asplenics

Question 10

All of the following statements about Lambda phage are true, EXCEPT:

Accepted Answer

Both the lytic and lysogenic phases occur simultaneously.

Answer

In the lysogenic phase, it integrates with the host chromosome and remains dormant.

Answer

In the lytic phase, it replicates and produces new phage particles.

Answer

In the lytic phase, it causes host cell lysis and releases progeny virus particles.

Virology — MCQs

Virology — MCQs

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