Virology Practice Questions

Q: What virus most commonly causes aplastic crisis in hemolytic anemia?

Parvovirus. **Explanation:** **Parvovirus B19** is the correct answer because it specifically targets and infects **erythroid progenitor cells** (pro-erythroblasts) in the bone marrow by binding to the **P-antigen** (globoside) on the cell surface. In healthy individuals, the temporary cessation of red blood cell (RBC) production is clinically silent. However, in patients with underlying **hemolytic anemias** (e.g., Sickle Cell Disease, Hereditary Spherocytosis, Thalassemia), where RBC lifespan is already shortened, this sudden halt in erythropoiesis leads to a life-threatening **Aplastic Crisis**, characterized by a plummeting hemoglobin level and a **reticulocytopenia** (low reticulocyte count). **Incorrect Options:** * **HIV (Option A):** While HIV causes chronic anemia of chronic disease and bone marrow suppression in advanced stages, it does not cause an acute aplastic crisis. * **Herpes virus (Option B):** Members like CMV or EBV can cause cytopenias or infectious mononucleosis, but they do not selectively target erythroid precursors. * **HTLV (Option D):** HTLV-1 is associated with Adult T-cell Leukemia/Lymphoma (ATLL) and tropical spastic paraparesis, not acute erythroid failure. **High-Yield Clinical Pearls for NEET-PG:** * **Erythema Infectiosum (Fifth Disease):** Parvovirus B19 causes the classic "slapped-cheek" rash in children. * **Hydrops Fetalis:** Maternal infection during pregnancy can lead to severe fetal anemia, high-output cardiac failure, and fetal death. * **Arthropathy:** In adults, it often presents as symmetrical small joint arthritis (mimicking Rheumatoid Arthritis). * **Diagnosis:** The most sensitive indicator of an acute aplastic crisis is a **low reticulocyte count** in the presence of worsening anemia.

Q: Which of the following is the most commonly vertically transmitted organism?

Cytomegalovirus. ### Explanation **Correct Answer: B. Cytomegalovirus (CMV)** **Why it is correct:** Cytomegalovirus (CMV) is the **most common cause of congenital (intrauterine) infection** worldwide, affecting approximately 0.2% to 2% of all live births. Unlike many other TORCH agents, CMV can be transmitted to the fetus during both primary maternal infection and reactivation (recurrent infection) due to its ability to establish latency. It is the leading non-genetic cause of sensorineural hearing loss and neurodevelopmental delays in children. **Analysis of Incorrect Options:** * **A. Herpes Simplex Virus (HSV):** While HSV can be transmitted vertically, it most commonly occurs **perinatally** (during delivery through an infected birth canal) rather than in utero. It is less frequent than CMV. * **C. Rubella Virus:** Although Rubella causes severe congenital rubella syndrome (CRS), its incidence has drastically declined in regions with robust MMR vaccination programs. It is no longer the "most common" due to effective immunization. * **D. Human Papillomavirus (HPV):** Vertical transmission of HPV is rare. When it occurs, it typically manifests as recurrent respiratory papillomatosis in the child, but it is not a frequent cause of congenital infection compared to the TORCH group. **NEET-PG High-Yield Pearls:** * **Most common clinical feature:** Most neonates (90%) are asymptomatic at birth. * **Classic Triad of Symptomatic CMV:** Periventricular calcifications (pathognomonic), microcephaly, and sensorineural hearing loss. * **Diagnosis:** The gold standard for congenital CMV is detecting the virus in **urine or saliva** via PCR within the first 3 weeks of life. * **Histology:** Look for "Owl’s eye" intranuclear inclusion bodies. * **Treatment:** Intravenous Ganciclovir or oral Valganciclovir is used for symptomatic neonates to reduce the severity of hearing loss.

Q: Which of the following is not a structural gene of HIV?

Tat. **Explanation:** The HIV genome is composed of three categories of genes: **Structural**, **Regulatory**, and **Accessory**. Understanding this classification is high-yield for NEET-PG. **Why Tat is the correct answer:** **Tat (Trans-activator of transcription)** is a **Regulatory gene**, not a structural one. Its primary function is to enhance the efficiency of viral transcription by binding to the TAR (trans-activation response) element, significantly increasing the production of viral mRNAs. Along with **Rev**, it is essential for viral replication. **Why the other options are incorrect:** The HIV genome contains three major **structural genes** that code for the physical components of the virion: * **Gag (Group-specific antigen):** Codes for internal core proteins, primarily **p24** (capsid), p17 (matrix), and p7/p9 (nucleocapsid). * **Pol (Polymerase):** Codes for vital enzymes required for the viral life cycle: **Reverse Transcriptase**, **Integrase**, and **Protease**. * **Env (Envelope):** Codes for the precursor gp160, which is cleaved into surface glycoproteins **gp120** (attachment to CD4) and **gp41** (fusion/transmembrane). **High-Yield Clinical Pearls for NEET-PG:** * **p24 Antigen:** The earliest serological marker of HIV infection (detected in the "window period"). * **gp120:** Responsible for tropism; it binds to the CD4 receptor and CCR5/CXCR4 co-receptors. * **Accessory Genes:** Include *vif, vpu, vpr,* and *nef*. **Nef** is particularly important as it downregulates CD4 and MHC-I expression, helping the virus evade the immune system. * **Regulatory Genes:** *Tat* and *Rev*.

Q: Which of the following statements about the P24 antigen of HIV is NOT true?

It remains during the asymptomatic phase.. ### Explanation **Why Option D is the Correct Answer (The False Statement):** The **p24 antigen** is the major internal capsid protein of HIV-1. During the natural course of infection, p24 levels rise sharply during the acute phase but **disappear or become undetectable during the asymptomatic (latent) phase**. This happens because the host’s immune system produces anti-p24 antibodies, which bind to the antigen to form immune complexes, effectively "clearing" free p24 from the serum. It only reappears later during the progression to AIDS as the immune system collapses. **Analysis of Other Options:** * **A. It can be detected during the window period:** This is true. The p24 antigen appears in the blood roughly 1–3 weeks after infection, well before the development of detectable antibodies (the "window period"). This makes it a crucial marker for early diagnosis. * **B. Free P24 antigen disappears after the appearance of IgM/IgG response:** This is true. As the humoral immune response kicks in, antibodies (initially IgM, then IgG) neutralize the free antigen, leading to its decline in the serum. * **C. Viral load parallels P24 titre:** This is true. p24 is a direct component of the virus; therefore, its concentration in the blood correlates with the level of active viral replication (viral load). **Clinical Pearls for NEET-PG:** * **4th Generation ELISA:** Also known as the "Combo" or "Duo" test, it detects both **p24 antigen and HIV-1/2 antibodies** simultaneously, significantly shortening the window period. * **Earliest Marker:** While p24 is the earliest *protein* marker, **HIV-RNA (via PCR)** is the overall earliest detectable marker of infection (detectable within 7–10 days). * **Prognostic Value:** A reappearance of p24 antigen in a previously asymptomatic patient indicates clinical deterioration and progression toward AIDS.

Q: Which type of Hepatitis is known to be transmitted vertically?

Hepatitis B. **Explanation:** **Hepatitis B Virus (HBV)** is the most common cause of vertical transmission (mother-to-child) among the hepatitis viruses. This transmission typically occurs **perinatally** during delivery through contact with maternal blood and vaginal secretions, or in utero (less common). The risk of transmission is highest (up to 90%) if the mother is positive for both HBsAg and HBeAg, indicating high viral replication. **Analysis of Options:** * **Hepatitis B (Correct):** It is a blood-borne DNA virus. Vertical transmission is a major route of infection globally, often leading to chronic carrier states in neonates (90% risk of chronicity if infected at birth). * **Hepatitis A & E:** These are transmitted via the **fecal-oral route**. While Hepatitis E is notorious for high mortality in pregnant women (up to 20%), it is not typically characterized by vertical transmission. * **Hepatitis C:** While vertical transmission of HCV is possible, the rate is significantly lower (approx. 3–5%) compared to HBV, making HBV the primary answer for this classic exam question. **High-Yield Clinical Pearls for NEET-PG:** * **Immunoprophylaxis:** To prevent vertical transmission, infants born to HBsAg-positive mothers must receive both the **HBV vaccine** and **Hepatitis B Immunoglobulin (HBIG)** within 12 hours of birth. * **Chronicity Rule:** The younger the age at the time of HBV infection, the higher the risk of developing chronic hepatitis. * **HBeAg Status:** The presence of HBeAg in the mother is the single most important predictor of vertical transmission risk.

Q: Most common involvement of the genitourinary system is seen in which of the following?

Herpes Simplex Virus 2 (HSV-2). **Explanation:** The correct answer is **Herpes Simplex Virus 2 (HSV-2)**. **1. Why HSV-2 is correct:** Historically and clinically, HSV-2 is the primary cause of **Genital Herpes**. It is predominantly transmitted through sexual contact and is the most common cause of recurrent genital ulcer disease worldwide. While HSV-1 can also cause genital lesions (and is increasing in frequency due to changing sexual practices), HSV-2 remains the classic and most frequent pathogen associated with the genitourinary system, characterized by painful vesicles, ulcers, and a high rate of latent reactivation in the **sacral ganglia**. **2. Why other options are incorrect:** * **HSV-1:** This virus is traditionally associated with **"above the waist"** infections, such as gingivostomatitis, herpes labialis (cold sores), and keratoconjunctivitis. It establishes latency in the **trigeminal ganglia**. * **HHV-8 (Human Herpesvirus 8):** Also known as Kaposi Sarcoma-associated Herpesvirus (KSHV), it is the causative agent of **Kaposi Sarcoma**, Primary Effusion Lymphoma, and Multicentric Castleman Disease, typically in immunocompromised patients. * **HSV-12:** This is a **distractor**. Human Herpesviruses are classified from 1 to 8 (HSV-1, HSV-2, VZV, EBV, CMV, HHV-6, HHV-7, and HHV-8). There is no medically recognized "HSV-12." **Clinical Pearls for NEET-PG:** * **Diagnosis:** Tzanck smear showing **Multinucleated Giant Cells** with Cowdry Type A intranuclear inclusions (non-specific for HSV-1 vs HSV-2). * **Gold Standard:** PCR is the most sensitive test for diagnosis. * **Neonatal Herpes:** Most commonly transmitted during birth via an infected maternal genital tract (usually HSV-2). * **Treatment:** Acyclovir is the drug of choice, which acts by inhibiting viral DNA polymerase.

Q: The 'bowl of spaghetti' appearance is characteristic of which of the following?

Ebola virions. **Explanation:** The characteristic **'bowl of spaghetti'** appearance refers to the unique morphology of **Ebola virions** when viewed under an electron microscope. Ebola belongs to the **Filoviridae** family (from the Latin *filum*, meaning thread). These viruses are pleomorphic, appearing as long, filamentous, non-segmented forms that can be straight, curved, or coiled into "6-shaped," "U-shaped," or circular configurations. When multiple long, intertwined filaments are present in a sample, they resemble a bowl of spaghetti. **Analysis of Options:** * **Ebola Virions (Correct):** As members of the Filoviridae family, their elongated, thread-like structure (up to 14,000 nm in length) creates the classic "spaghetti" or "shepherd’s crook" appearance. * **Adenovirus:** These are non-enveloped, **icosahedral** viruses with fibers protruding from the vertices (pentons), giving them a "space satellite" or "soccer ball" appearance. * **Marburg Virus:** While also a Filovirus, Marburg typically presents as shorter filaments or distinct "6-shaped" structures. While morphologically similar to Ebola, the specific descriptive term 'bowl of spaghetti' is most classically associated with Ebola in standardized medical literature. * **Poliovirus:** A member of the Picornaviridae family, it is a very small (approx. 30 nm), simple **icosahedral** virus. **High-Yield NEET-PG Pearls:** * **Filoviridae Characteristics:** Negative-sense ssRNA, enveloped, helical nucleocapsid. * **Transmission:** Direct contact with infected blood, secretions, or organs (often via fruit bats as natural reservoirs). * **Diagnosis:** Gold standard for early detection is **RT-PCR**. Electron microscopy is used for structural identification. * **Other "Shapes":** * **Rabies:** Bullet-shaped. * **Poxvirus:** Brick-shaped. * **Rotavirus:** Wheel-like (*Rota* = wheel).

Q: Human papillomavirus (HPV) type 6 is most often implicated in the causation of which of the following conditions?

Condyloma acuminata. **Explanation:** **Condyloma acuminata**, also known as anogenital warts, are primarily caused by **Human Papillomavirus (HPV) types 6 and 11**. These are considered "low-risk" HPV types because they have a low potential for malignant transformation but are highly infectious and responsible for approximately 90% of genital warts. They typically present as cauliflower-like, flesh-colored growths in the perineal and perianal regions. **Analysis of Incorrect Options:** * **A. Cervical cancer:** This is primarily associated with "high-risk" HPV types, most notably **HPV 16 and 18**. These types produce E6 and E7 oncoproteins that inhibit tumor suppressor genes p53 and Rb, respectively. * **C. Flat warts (Verruca plana):** These are smooth, flat-topped papules commonly found on the face and dorsum of hands. They are most frequently associated with **HPV types 3 and 10**. * **D. Common warts (Verruca vulgaris):** These hyperkeratotic, dome-shaped papules are most commonly caused by **HPV types 2 and 4** (and sometimes type 1). **High-Yield Clinical Pearls for NEET-PG:** * **HPV 1:** Most common cause of deep **plantar warts** (myrmecia). * **HPV 5 and 8:** Associated with **Epidermodysplasia verruciformis** and a high risk of Squamous Cell Carcinoma (SCC). * **Butcher’s Warts:** Caused by **HPV 7**. * **Heck’s Disease (Focal Epithelial Hyperplasia):** Associated with **HPV 13 and 32**. * **Histopathology:** Look for **koilocytes** (keratinocytes with perinuclear halos and pyknotic nuclei), which are pathognomonic for HPV infection.

Question 1

What virus most commonly causes aplastic crisis in hemolytic anemia?

Accepted Answer

Parvovirus

Answer

HIV

Answer

Herpes virus

Answer

HTLV

Question 2

Which of the following is the most commonly vertically transmitted organism?

Accepted Answer

Cytomegalovirus

Answer

Herpes simplex virus

Answer

Rubella virus

Answer

Human papillomavirus

Question 3

Which of the following is not a structural gene of HIV?

Accepted Answer

Tat

Answer

Gag

Answer

Pol

Answer

ENV

Question 4

The protein of envelope is found in which of the following virus families?

Accepted Answer

Myxovirus

Answer

Togavirus

Answer

Parvovirus

Answer

Adenovirus

Question 5

Which of the following statements about the P24 antigen of HIV is NOT true?

Accepted Answer

It remains during the asymptomatic phase.

Answer

It can be detected during the window period.

Answer

Free P24 antigen disappears after the appearance of IgM response to it.

Answer

Viral load parallels P24 titre.

Question 6

Which type of Hepatitis is known to be transmitted vertically?

Accepted Answer

Hepatitis B

Answer

Hepatitis A

Answer

Hepatitis E

Answer

Hepatitis C

Question 7

Most common involvement of the genitourinary system is seen in which of the following?

Accepted Answer

Herpes Simplex Virus 2 (HSV-2)

Answer

Herpes Simplex Virus 1 (HSV-1)

Answer

Herpes Simplex Virus 8 (HSV-8)

Answer

Herpes Simplex Virus 12 (HSV-12)

Question 8

Parvovirus infection is associated with which of the following conditions?

Accepted Answer

None of the above

Answer

Hydrops fetalis

Answer

Aplastic crisis

Answer

Sixth disease

Question 9

The 'bowl of spaghetti' appearance is characteristic of which of the following?

Accepted Answer

Ebola virions

Answer

Adenovirus

Answer

Marburg Viruses

Answer

Poliovirus

Question 10

Human papillomavirus (HPV) type 6 is most often implicated in the causation of which of the following conditions?

Accepted Answer

Condyloma acuminata

Answer

Cervical cancer

Answer

Flat warts

Answer

Common warts

Virology — MCQs

Virology — MCQs

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