Virology Practice Questions

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.

Q: Which of the following contains an RNA-dependent DNA polymerase as a structural component of the virion?

RNA tumor viruses. **Explanation:** The correct answer is **RNA tumor viruses** (Retroviruses). **1. Why RNA tumor viruses are correct:** RNA tumor viruses, such as Human T-cell Lymphotropic Virus (HTLV) and HIV, belong to the **Retroviridae** family. These viruses are unique because they possess the enzyme **Reverse Transcriptase (RNA-dependent DNA polymerase)** as an integral structural component within the viral capsid. This enzyme allows the virus to transcribe its single-stranded RNA genome into double-stranded DNA, which then integrates into the host cell's genome (provirus). This step is essential for replication and oncogenic transformation. **2. Why the other options are incorrect:** * **Adenoviruses (Option A):** These are non-enveloped **dsDNA** viruses. They use host cell DNA-dependent DNA polymerase for replication and do not require reverse transcriptase. * **Orthomyxoviruses (Option B):** (e.g., Influenza virus) These are negative-sense ssRNA viruses. They carry an **RNA-dependent RNA polymerase** (RdRp) to synthesize mRNA, but they do not produce DNA intermediates. * **Rhabdoviruses (Option C):** (e.g., Rabies virus) Like Orthomyxoviruses, these are negative-sense ssRNA viruses that carry their own **RNA-dependent RNA polymerase** (RdRp) within the virion, not a DNA polymerase. **High-Yield Clinical Pearls for NEET-PG:** * **Reverse Transcriptase** has three activities: RNA-dependent DNA polymerase, RNase H (degrades RNA from RNA-DNA hybrid), and DNA-dependent DNA polymerase. * **Hepatitis B Virus (Hepadnaviridae)** also uses reverse transcriptase during its replication cycle, but unlike Retroviruses, it is a **DNA virus** that packages the enzyme to convert an RNA intermediate back into DNA. * **RNA-dependent RNA polymerase** is a structural component of all **negative-sense RNA viruses** (e.g., Ortho-, Paramyxo-, Rhabdo-, Filo-, and Bunyaviruses).

Q: Evaluation of a specimen from a patient with hepatocellular carcinoma demonstrates the presence of a single-stranded RNA virus. Which of the following is the most probable etiological agent?

Hepatitis C virus. ### Explanation The correct answer is **Hepatitis C virus (HCV)**. **1. Why Hepatitis C is correct:** Hepatitis C is a **single-stranded RNA (ssRNA)** virus belonging to the *Flaviviridae* family. It is a major risk factor for the development of Hepatocellular Carcinoma (HCC). Unlike DNA viruses, HCV does not integrate into the host genome; instead, it promotes oncogenesis through chronic inflammation, oxidative stress, and the action of non-structural proteins (like NS5A) that interfere with cell cycle regulation and apoptosis. Active infection is confirmed by the presence of serum hepatitis C RNA [1]. **2. Why other options are incorrect:** * **Hepatitis B virus (HBV):** While HBV is a leading cause of HCC worldwide, it is a **partially double-stranded DNA virus** (*Hepadnaviridae*). It can cause HCC even without cirrhosis due to its ability to integrate into the host DNA. * **Hepatitis A (HAV) and Hepatitis E (HEV):** Both are RNA viruses transmitted via the fecal-oral route [3]. However, they cause **acute hepatitis** only and do not lead to chronic infection, cirrhosis, or an increased risk of HCC. (Note: HEV can be chronic in immunocompromised patients, but it is not typically linked to HCC). **3. High-Yield Clinical Pearls for NEET-PG:** * **Genome Type:** Remember the mnemonic "All Hepatitis viruses are RNA except **B** (DNA)." * **HCC Risk:** In the presence of cirrhosis, HCV has a higher annual risk of progressing to HCC compared to HBV. * **Screening:** Patients with chronic HCV and cirrhosis should undergo HCC surveillance every 6 months using **Ultrasonography +/- Alpha-fetoprotein (AFP)** [2]. * **Treatment:** Direct-acting antivirals (DAAs) can achieve a Sustained Virologic Response (SVR), significantly reducing but not entirely eliminating the risk of HCC.

Q: Which of the following does not indicate Hepatitis B replication?

HBcAg. **Explanation:** The correct answer is **HBcAg (Hepatitis B core Antigen)**. In clinical practice, **HBcAg is not detectable in the serum** because it is sequestered within the viral envelope (HBsAg). It remains localized within the hepatocyte nuclei. Therefore, its presence in a standard blood report cannot be used to monitor active viral replication. Instead, we measure **Anti-HBc antibodies** to determine exposure. **Why the other options are markers of replication:** * **HBeAg (Hepatitis B envelope Antigen):** This is a soluble protein secreted by the virus during active replication. Its presence in serum indicates high infectivity and active viral multiplication. * **HBV DNA:** This is the most sensitive and specific quantitative marker for viral load. It directly measures the genetic material of the virus in the blood. * **Viral copies:** This is simply the numerical quantification of HBV DNA. High copy numbers correlate directly with active replication and the risk of liver damage. **NEET-PG High-Yield Pearls:** 1. **Window Period:** The time between the disappearance of HBsAg and the appearance of Anti-HBs. During this phase, **Anti-HBc IgM** is the only diagnostic marker present. 2. **Pre-core Mutant:** A condition where the patient is HBeAg negative but has high HBV DNA levels. This occurs due to a mutation in the pre-core region that prevents HBeAg secretion despite active replication. 3. **HBsAg:** The first marker to appear in blood after infection; its persistence beyond 6 months defines chronic hepatitis B. 4. **Anti-HBs:** Indicates immunity (either through recovery or vaccination).

Q: Which of the following viruses is brick-shaped?

Small pox. **Explanation:** The correct answer is **Smallpox (Variola virus)**. **1. Why Smallpox is correct:** Smallpox belongs to the **Poxviridae** family. Poxviruses are the largest and most complex of all animal viruses. Under electron microscopy, they exhibit a characteristic **brick-shaped** (rectangular) morphology with a complex internal structure consisting of a biconcave core and two lateral bodies. This is a classic high-yield morphological feature often tested in NEET-PG. **2. Why the other options are incorrect:** * **Chickenpox (Varicella-Zoster Virus), CMV (Cytomegalovirus), and EBV (Epstein-Barr Virus):** All three belong to the **Herpesviridae** family. Herpesviruses are characterized by an **icosahedral** capsid symmetry and are **spherical** in overall shape due to their lipid envelope. They are significantly smaller than poxviruses. **3. Clinical Pearls & High-Yield Facts for NEET-PG:** * **Size:** Poxviruses are the only viruses large enough to be seen under a light microscope (using special stains like Paschen’s stain). * **Replication:** Unlike most DNA viruses that replicate in the nucleus, Poxviruses replicate entirely in the **cytoplasm** because they carry their own DNA-dependent RNA polymerase. * **Inclusion Bodies:** Smallpox produces intracytoplasmic inclusion bodies known as **Guarnieri bodies**. * **Eradication:** Smallpox is the only human infectious disease to be globally eradicated (declared by the WHO in 1980). * **Molluscum Contagiosum:** Another member of the Poxviridae family, it also shares the brick-shaped morphology and produces Henderson-Patterson bodies.

Q: Which of the following statement is TRUE about polio?

Increased muscular activity leads to increased paralysis. **Explanation:** The correct answer is **C: Increased muscular activity leads to increased paralysis.** This is a high-yield concept in Polio pathogenesis known as **"Provocation Polio."** During the pre-paralytic stage of the infection, excessive physical activity or muscular trauma (like IM injections) increases the risk and severity of paralysis in the specific muscle groups involved. This occurs because increased metabolic activity in the motor neurons facilitates the entry and replication of the poliovirus within the anterior horn cells of the spinal cord. **Analysis of Incorrect Options:** * **A. Paralytic polio is most common:** Incorrect. In reality, **Inapparent/Asymptomatic infection** is the most common outcome (>90-95%). Paralytic polio occurs in less than 1% of cases. * **B. Spastic paralysis:** Incorrect. Poliovirus specifically destroys the **Lower Motor Neurons (LMN)** in the anterior horn of the spinal cord. This results in **Asymmetrical Flaccid Paralysis** with loss of deep tendon reflexes, not spasticity. * **D. Polio vaccine is given orally:** While the Oral Polio Vaccine (OPV/Sabin) is given orally, this option is considered "less true" in a competitive context compared to the physiological fact in Option C. Furthermore, the global shift (including India’s Universal Immunization Programme) now emphasizes the **Inactivated Polio Vaccine (IPV)**, which is given via IM or intradermal routes. **High-Yield Clinical Pearls for NEET-PG:** * **Specimen of choice:** Stool (virus is excreted for weeks). * **Most common site of paralysis:** Spinal (legs > arms). * **Post-Polio Syndrome:** Occurs 30–40 years after recovery due to the gradual failure of over-extended motor neurons. * **Last case in India:** 13th January 2011 (Howrah, West Bengal). India was declared Polio-free in 2014.

Q: Which virus has a segmented genome?

Rotavirus. **Explanation:** The concept of a **segmented genome** is a high-yield topic in virology. Most viruses have a single continuous piece of nucleic acid, but some RNA viruses have genomes divided into separate pieces (segments). This allows for **genetic reassortment**, leading to significant antigenic shifts. **1. Why Rotavirus is Correct:** Rotavirus belongs to the **Reoviridae** family. It is characterized by a **double-stranded RNA (dsRNA)** genome consisting of **11 segments**. This segmentation is crucial for its genetic diversity. Clinically, Rotavirus is the most common cause of severe dehydrating diarrhea in infants and young children worldwide. **2. Analysis of Incorrect Options:** * **Retrovirus (e.g., HIV):** These possess a **diploid** genome (two identical copies of single-stranded RNA), but the genome itself is not segmented. * **Poliovirus:** A member of the **Picornaviridae** family, it has a single-stranded, positive-sense, **non-segmented** RNA genome. * **Rhabdovirus (e.g., Rabies):** This is a bullet-shaped virus with a single-stranded, negative-sense, **non-segmented** RNA genome. **3. NEET-PG High-Yield Clinical Pearls:** To remember the segmented RNA viruses, use the mnemonic **"BOAR"**: * **B**unyaviridae (3 segments) * **O**rthomyxoviridae (e.g., Influenza; 8 segments) * **A**renaviridae (2 segments) * **R**eoviridae (e.g., Rotavirus; 11 segments) **Key Fact:** Genetic reassortment in segmented viruses (especially Influenza) is the mechanism behind **Antigenic Shift**, which leads to pandemics. In contrast, **Antigenic Drift** (point mutations) occurs in both segmented and non-segmented viruses.

Question 1

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 2

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 3

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.

Question 4

Which of the following contains an RNA-dependent DNA polymerase as a structural component of the virion?

Accepted Answer

RNA tumor viruses

Answer

Adenoviruses

Answer

Orthomyxoviruses

Answer

Rhabdoviruses

Question 5

Evaluation of a specimen from a patient with hepatocellular carcinoma demonstrates the presence of a single-stranded RNA virus. Which of the following is the most probable etiological agent?

Accepted Answer

Hepatitis C virus

Answer

Hepatitis A virus

Answer

Hepatitis B virus

Answer

Hepatitis E virus

Question 6

Which of the following does not indicate Hepatitis B replication?

Accepted Answer

HBcAg

Answer

HBeAg

Answer

HBV DNA

Answer

Viral copies

Question 7

Reverse transcriptase sequence in HIV is best described as:

Accepted Answer

RNA - DNA - RNA

Answer

DNA - RNA

Answer

DNA - RNA - DNA

Answer

RNA - DNA

Question 8

Which of the following viruses is brick-shaped?

Accepted Answer

Small pox

Answer

Chicken pox

Answer

CMV

Answer

EBV

Question 9

Which of the following statement is TRUE about polio?

Accepted Answer

Increased muscular activity leads to increased paralysis

Answer

Paralytic polio is most common

Answer

Spastic paralysis

Answer

Polio vaccine is given orally

Question 10

Which virus has a segmented genome?

Accepted Answer

Rotavirus

Answer

Retrovirus

Answer

Poliovirus

Answer

Rhabdovirus

Virology — MCQs

Virology — MCQs

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