Virology Practice Questions

Q: A viral organism was isolated from a painful blister on the lip of a teenage girl. The agent was found to have double-stranded, linear DNA and was enveloped. The patient had a similar sore approximately 2 months ago. Which of the following is the most likely causative organism?

Herpes simplex type 1 virus. ### Explanation **Correct Answer: C. Herpes simplex type 1 virus (HSV-1)** The clinical presentation of a painful blister on the lip (herpes labialis) in a teenager, combined with a history of recurrence, is classic for **Herpes simplex virus type 1 (HSV-1)**. * **Virology:** HSV-1 is a member of the *Herpesviridae* family, characterized by a **double-stranded, linear DNA** genome and a lipid **envelope** derived from the host nuclear membrane. * **Pathogenesis:** After the primary infection, the virus remains **latent** in the sensory nerve ganglia (specifically the **trigeminal ganglion** for oral lesions). Periodic reactivation leads to recurrent sores, often triggered by stress, sunlight, or fever. **Incorrect Options:** * **A. Adenovirus:** While it has dsDNA, it is **non-enveloped**. It typically causes pharyngoconjunctival fever or keratoconjunctivitis, not recurrent vesicular lip sores. * **B. Coxsackie virus:** Part of the *Picornaviridae* family, it has a **ssRNA** genome and is **non-enveloped**. It causes Herpangina or Hand-Foot-Mouth disease, which present as ulcers but do not typically recur in the same site. * **D. Herpes zoster virus (VZV):** Although it is an enveloped dsDNA virus, it typically presents as a **dermatomal** rash (shingles) in older or immunocompromised individuals. Recurrence twice within two months in a teenager is highly atypical for VZV. **High-Yield Clinical Pearls for NEET-PG:** * **Tzanck Smear:** Look for **multinucleated giant cells** and **Cowdry Type A** intranuclear inclusion bodies. * **Latency Site:** HSV-1 (Trigeminal ganglion); HSV-2 (Sacral ganglion); VZV (Dorsal root ganglion). * **Drug of Choice:** Acyclovir (inhibits viral DNA polymerase). * **Enveloping:** Herpesviruses are unique because they acquire their envelope by budding through the **inner nuclear membrane**.

Q: A male patient is HBsAg positive, HBeAg negative, and anti-HBe antibody positive. HBV DNA copies are 100,000/ml, and SGOT and SGPT are elevated to 6 times the upper limit of normal. What is the likely diagnosis?

HBV precore mutant. ### Explanation The correct answer is **HBV precore mutant**. In a typical (wild-type) Hepatitis B infection, the presence of **HBeAg** indicates active viral replication and high infectivity. However, in a **precore mutant** (most commonly a G-to-A mutation at nucleotide 1896), the virus develops a stop codon that prevents the production of HBeAg, even though the virus continues to replicate vigorously. **Why it is the correct diagnosis:** The patient presents with a "discordant" profile: **HBeAg is negative** and **anti-HBe is positive** (suggesting low replication), yet the **HBV DNA is high** (100,000 copies/ml) and **ALT/AST are significantly elevated** (6x normal). This combination of negative HBeAg with high DNA and active liver inflammation is the hallmark of a precore mutant infection. **Why other options are incorrect:** * **HBV surface mutant:** This involves mutations in the 'a' determinant of HBsAg. These patients are typically HBsAg negative but HBV DNA positive (occult infection). * **Wild HBsAg:** In wild-type infection, high viral replication (high DNA) would almost always be accompanied by a **positive HBeAg**. * **Inactive HBV carrier:** While these patients are HBeAg negative and anti-HBe positive, they must have **low/undetectable HBV DNA** ( 2,000 IU/ml and ALT is elevated. * **Serological Gap:** If a patient has high DNA but is HBeAg negative, always suspect a mutant strain.

Q: Hepatitis C virus resembles which of the following virus groups?

Flaviviruses. ### Explanation **Correct Option: D (Flaviviruses)** Hepatitis C Virus (HCV) is classified under the family **Flaviviridae** and the genus *Hepacivirus*. It resembles other Flaviviruses (like Yellow Fever or Dengue virus) because it is an **enveloped, positive-sense single-stranded RNA (+ssRNA)** virus. A key structural characteristic it shares with this group is its genomic organization and the presence of an icosahedral nucleocapsid. **Why other options are incorrect:** * **Picornaviruses (Option A):** While Hepatitis A (HAV) belongs to this family, Picornaviruses are **non-enveloped** RNA viruses. HCV is enveloped. * **Herpesviruses (Option B):** These are large, **enveloped double-stranded DNA (dsDNA)** viruses. Their replication and structure are entirely different from the RNA-based HCV. * **Hepadnaviruses (Option C):** This family includes Hepatitis B Virus (HBV). Hepadnaviruses are **partially double-stranded DNA** viruses that utilize reverse transcriptase, unlike the direct RNA replication of HCV. **High-Yield Clinical Pearls for NEET-PG:** * **Genomic Stability:** HCV lacks 3'-5' exonuclease activity (proofreading), leading to high antigenic variation and the formation of **quasispecies**. This is the primary reason why a vaccine for HCV has not yet been developed. * **Transmission:** Primarily parenteral (blood-borne). It has the highest rate of progression to **chronic infection** (~80%) among all hepatitis viruses. * **Diagnosis:** Screening is done via Anti-HCV antibodies (ELISA); confirmation and viral load are assessed via **HCV-RNA (PCR)**. * **Association:** Strongly linked to Cryoglobulinemia and Hepatocellular Carcinoma (HCC).

Q: Which influenza strain has caused a pandemic?

H1N1. **Explanation:** Influenza pandemics occur due to **Antigenic Shift**, a process where a major change in the surface glycoproteins (Hemagglutinin and Neuraminidase) occurs, usually through genetic reassortment between human and animal viruses. This results in a novel virus to which the global population has little to no immunity. **Why H1N1 is correct:** **H1N1** is the most significant pandemic strain in history. It was responsible for the **1918 Spanish Flu** (the deadliest pandemic) and the **2009 Swine Flu** pandemic. Because it successfully adapted for efficient human-to-human transmission, it spread globally. **Analysis of Incorrect Options:** * **H2N2:** While H2N2 caused the 1957 Asian Flu pandemic, it is not the *only* answer. However, in the context of this specific question format, H1N1 is the most frequently tested and clinically relevant prototype for pandemics. (Note: If this were a "Multiple Correct" style, H2N2 would also be a candidate, but H1N1 remains the primary answer). * **H5N1:** Known as **Avian Influenza (Bird Flu)**. While it has a high mortality rate in humans, it has **not** caused a pandemic because it lacks the ability for sustained human-to-human transmission. * **H9N1:** This is a subtype of avian influenza that occasionally infects humans but has never caused a pandemic or widespread outbreaks. **High-Yield Clinical Pearls for NEET-PG:** * **Antigenic Shift:** Major change (reassortment); causes **Pandemics**. Seen only in Influenza A. * **Antigenic Drift:** Minor change (point mutations); causes **Epidemics**. Seen in both Influenza A and B. * **Drug of Choice:** Oseltamivir (Neuraminidase inhibitor) is the treatment for both seasonal and pandemic H1N1. * **Pandemic Years to Remember:** 1918 (H1N1), 1957 (H2N2), 1968 (H3N2), and 2009 (H1N1).

Q: Segmented genome is found in all of the following viruses except?

Rhabdovirus. ### Explanation The concept of a **segmented genome** is a high-yield topic in virology. Viruses with segmented genomes can undergo **genetic reassortment** (antigenic shift), leading to the emergence of new strains and potential pandemics. **1. Why Rhabdovirus is the Correct Answer:** Rhabdoviruses (e.g., Rabies virus) possess a **non-segmented, single-stranded, negative-sense RNA genome**. Their genetic material is a continuous linear molecule, meaning they cannot undergo reassortment. Morphologically, they are characterized by a distinct bullet-shaped appearance. **2. Analysis of Incorrect Options:** To remember segmented viruses, use the mnemonic **"BOAR"**: * **B - Bunyavirus (Option C):** Contains **3 segments** (Large, Medium, Small). Examples include Hantavirus and Crimean-Congo hemorrhagic fever virus. * **O - Orthomyxovirus (Option A):** Includes **Influenza virus**, which has **8 segments** (Influenza A and B) or 7 segments (Influenza C). This segmentation is the basis for antigenic shift. * **A - Arenavirus:** Contains **2 segments** (Large and Small). Examples include Lassa fever virus. * **R - Reovirus (Option B):** The only double-stranded RNA virus in this list, containing **10–12 segments**. Rotavirus (a member of this family) typically has 11 segments. **Clinical Pearls for NEET-PG:** * **Antigenic Shift:** Occurs only in segmented viruses (primarily Influenza A) due to reassortment of segments. * **Antigenic Drift:** Occurs in all viruses due to point mutations. * **Reovirus:** Remember it as "Double-Double" (Double-stranded and Double-layered capsid). * **Rabies (Rhabdovirus):** Look for **Negri bodies** (intracytoplasmic inclusions) in Purkinje cells of the cerebellum or pyramidal cells of the hippocampus.

Q: What is the highest risk factor for perinatal transmission when a mother is positive for a specific marker?

HBeAg. **Explanation:** The risk of vertical transmission of Hepatitis B Virus (HBV) from mother to child is primarily determined by the mother's viral load and replicative status. **Why HBeAg is the Correct Answer:** **HBeAg (Hepatitis B e-antigen)** is a marker of **active viral replication** and high infectivity. If a pregnant woman is positive for both HBsAg and HBeAg, the risk of vertical transmission to the newborn is approximately **70% to 90%** in the absence of immunoprophylaxis. Conversely, if the mother is HBsAg positive but HBeAg negative (and anti-HBe positive), the transmission risk drops significantly to about 10% to 40%. **Analysis of Incorrect Options:** * **HBsAg (Hepatitis B surface antigen):** While this indicates that the mother is a carrier or has an active infection, it does not specify the level of infectivity as accurately as HBeAg does. * **IgM anti-HBc (not HBsAg):** This indicates an acute infection but is not the primary determinant of transmission risk compared to the e-antigen status. * **IgG anti-HBs:** This represents **immunity** (either from past infection or vaccination). A mother with these antibodies cannot transmit the virus to the fetus; rather, she provides protective passive immunity. **High-Yield Clinical Pearls for NEET-PG:** * **Most common timing:** Most vertical transmission occurs **during delivery** (peripartum) through exposure to maternal blood and vaginal secretions. * **Prevention:** To prevent transmission, the newborn must receive both the **HBV Vaccine** and **Hepatitis B Immunoglobulin (HBIG)** within 12 hours of birth. This reduces the risk by >90%. * **Chronic Status:** Infants infected at birth have a **90% risk** of developing chronic Hepatitis B, compared to only a 5-10% risk if infected during adulthood.

Q: Which of the following viruses appears to be involved in the pathogenesis of Kaposi's sarcoma?

Human Herpes Virus 8. ### Explanation **Correct Answer: C. Human Herpes Virus 8 (HHV-8)** **Pathogenesis:** Kaposi’s Sarcoma (KS) is a vascular neoplasm caused by **Human Herpes Virus 8 (HHV-8)**, also known as **Kaposi Sarcoma-associated Herpesvirus (KSHV)** [1]. HHV-8 infects vascular and lymphatic endothelial cells. The virus carries genes that mimic host cellular genes (like v-cyclin and v-IL6), which promote cell proliferation, inhibit apoptosis, and induce angiogenesis (via VEGF). It is most commonly seen in the context of HIV/AIDS (Epidemic KS), but also occurs in elderly Mediterranean men (Classic KS), organ transplant recipients (Iatrogenic KS), and endemic regions of Africa [1]. **Analysis of Incorrect Options:** * **A. Human Herpes Virus 3 (Varicella-Zoster Virus):** Causes chickenpox (primary infection) and shingles (reactivation). It is not oncogenic. * **B. Human Herpes Virus 1 (Herpes Simplex Virus-1):** Primarily causes orolabial herpes (cold sores) and sporadic encephalitis. * **D. Human Herpes Virus 4 (Epstein-Barr Virus):** While EBV is oncogenic, it is associated with Burkitt lymphoma, Nasopharyngeal carcinoma, and Hodgkin lymphoma, but not Kaposi’s sarcoma [1]. **High-Yield NEET-PG Pearls:** * **Histology:** Look for **spindle-shaped cells**, slit-like vascular spaces, and extravasated RBCs with hemosiderin-laden macrophages. * **Marker:** **LANA-1** (Latency-Associated Nuclear Antigen) is a highly specific immunohistochemical marker for HHV-8 in tissue sections. * **Clinical Presentation:** Characterized by purple, red, or brown skin plaques or nodules, often involving the lower extremities, mucous membranes, or viscera [1]. * **Association:** HHV-8 is also implicated in **Primary Effusion Lymphoma (PEL)** and **Multicentric Castleman Disease**. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 261-262.

Q: Which virus is responsible for non-immune hydrops fetalis?

Parvovirus. **Explanation:** **Parvovirus B19** is the most common viral cause of **non-immune hydrops fetalis**. The virus specifically targets and infects **erythroid progenitor cells** (via the P-antigen receptor), leading to a temporary cessation of red blood cell production. In a fetus, who has a high rate of erythrocyte turnover and an expanding blood volume, this results in **severe fetal anemia**. The resulting high-output cardiac failure leads to generalized edema (anasarca), pleural/pericardial effusions, and ascites—collectively known as hydrops fetalis. **Analysis of Incorrect Options:** * **A. Cytomegalovirus (CMV):** While CMV is the most common congenital infection, it typically presents with periventricular calcifications, microcephaly, and sensorineural hearing loss rather than hydrops. * **B. Herpes Simplex Virus (HSV):** Neonatal HSV is usually acquired during delivery (birth canal) and presents as skin-eye-mouth (SEM) lesions, encephalitis, or disseminated disease, but not typically as hydrops. * **C. Hepatitis B Virus (HBV):** HBV is transmitted vertically but is not teratogenic and does not cause fetal structural anomalies or hydrops; it primarily leads to chronic carrier status in the neonate. **High-Yield Clinical Pearls for NEET-PG:** * **Fifth Disease:** Parvovirus B19 causes Erythema Infectiosum ("Slapped cheek" appearance) in children. * **Aplastic Crisis:** It can cause transient aplastic crisis in patients with underlying hemolytic anemias (e.g., Sickle Cell, Spherocytosis). * **Diagnosis:** Fetal hydrops is diagnosed via ultrasound; maternal infection is confirmed via IgM antibodies or PCR. * **Management:** Intrauterine blood transfusion (IUT) can be life-saving for the hydropic fetus.

Q: Which of the following is NOT an oncogenic virus?

Herpes simplex virus. **Explanation:** The correct answer is **Herpes simplex virus (HSV)**. While many members of the Herpesviridae family are associated with malignancy, HSV-1 and HSV-2 are primarily associated with acute and recurrent mucosal infections (cold sores and genital herpes) and have **not** been proven to be oncogenic in humans. **Why the other options are incorrect (Oncogenic Viruses):** * **Human Papillomavirus (HPV):** High-risk types (16, 18) are the primary cause of cervical, anogenital, and oropharyngeal cancers. They produce E6 and E7 oncoproteins which inhibit tumor suppressors p53 and pRb, respectively. * **Epstein-Barr Virus (EBV):** A potent oncogenic virus associated with Burkitt lymphoma, Nasopharyngeal carcinoma, Hodgkin lymphoma, and Post-transplant lymphoproliferative disorder (PTLD). * **Hepatitis B Virus (HBV):** A DNA virus that causes chronic inflammation and integrates into the host genome (via the HBx protein), significantly increasing the risk of Hepatocellular Carcinoma (HCC). **High-Yield Clinical Pearls for NEET-PG:** * **RNA Oncogenic Viruses:** Human T-cell Lymphotropic Virus-1 (HTLV-1) and Hepatitis C Virus (HCV) are the key RNA viruses linked to cancer. * **HHV-8:** Also known as Kaposi Sarcoma-associated Herpesvirus (KSHV), it is the herpesvirus most strongly linked to malignancy (Kaposi sarcoma and Primary effusion lymphoma). * **Mechanism:** Most DNA oncogenic viruses act by neutralizing host "gatekeeper" proteins like **p53** and **pRb**.

Q: A child presents with mononucleosis-like symptoms, but the test for mononucleosis and EBV titers are negative. What is a common cause of heterophile-negative mononucleosis?

Cytomegalovirus. ### Explanation **Correct Answer: A. Cytomegalovirus (CMV)** **Why it is correct:** Infectious Mononucleosis (IM) is most commonly caused by the Epstein-Barr Virus (EBV). However, approximately 10% of mononucleosis-like syndromes are **heterophile-negative**, meaning the Monospot test (which detects IgM antibodies that agglutinate horse/sheep RBCs) is negative. **Cytomegalovirus (CMV)** is the most common cause of heterophile-negative mononucleosis. While clinical features like fever and atypical lymphocytosis are similar to EBV, CMV mononucleosis typically presents with **milder pharyngitis** and **less prominent lymphadenopathy or splenomegaly.** **Why the other options are incorrect:** * **B. Herpes simplex virus (HSV):** Primarily causes gingivostomatitis, herpes labialis, or encephalitis; it does not typically present with a mononucleosis-like syndrome or atypical lymphocytosis. * **C. Varicella-zoster virus (VZV):** Causes chickenpox and shingles, characterized by a distinct vesicular rash in different stages of evolution. * **D. Adenovirus:** While it can cause pharyngitis and conjunctivitis (pharyngoconjunctival fever), it does not produce the systemic atypical lymphocytosis characteristic of mononucleosis. **High-Yield Clinical Pearls for NEET-PG:** * **The "Big Three" of Heterophile-Negative IM:** 1. CMV (Most common), 2. Acute HIV infection, 3. Toxoplasmosis. * **Diagnostic Hallmark:** Look for "Owl’s eye" intranuclear inclusion bodies in biopsy (though diagnosis is usually serological or via PCR). * **Drug Reaction:** Like EBV, giving **Ampicillin/Amoxicillin** in CMV mononucleosis can trigger a maculopapular skin rash. * **Atypical Lymphocytes:** These are actually **activated T-cells (CD8+)** reacting against the B-cells infected by the virus.

Question 1

A viral organism was isolated from a painful blister on the lip of a teenage girl. The agent was found to have double-stranded, linear DNA and was enveloped. The patient had a similar sore approximately 2 months ago. Which of the following is the most likely causative organism?

Accepted Answer

Herpes simplex type 1 virus

Answer

Adenovirus

Answer

Coxsackie virus

Answer

Herpes zoster virus

Question 2

A male patient is HBsAg positive, HBeAg negative, and anti-HBe antibody positive. HBV DNA copies are 100,000/ml, and SGOT and SGPT are elevated to 6 times the upper limit of normal. What is the likely diagnosis?

Accepted Answer

HBV precore mutant

Answer

HBV surface mutant

Answer

Wild HBsAg

Answer

Inactive HBV carrier

Question 3

Hepatitis C virus resembles which of the following virus groups?

Accepted Answer

Flaviviruses

Answer

Picornaviruses

Answer

Herpesviruses

Answer

Hepadnaviruses

Question 4

Which influenza strain has caused a pandemic?

Accepted Answer

H1N1

Answer

H2N2

Answer

H5N1

Answer

H9N1

Question 5

Segmented genome is found in all of the following viruses except?

Accepted Answer

Rhabdovirus

Answer

Influenza virus

Answer

Reovirus

Answer

Bunyavirus

Question 6

What is the highest risk factor for perinatal transmission when a mother is positive for a specific marker?

Accepted Answer

HBeAg

Answer

HBsAg

Answer

IgM anti HBsAg

Answer

IgG anti HBsAg

Question 7

Which of the following viruses appears to be involved in the pathogenesis of Kaposi's sarcoma?

Accepted Answer

Human Herpes Virus 8

Answer

Human Herpes Virus 3

Answer

Human Herpes Virus 1

Answer

Human Herpes Virus 4

Question 8

Which virus is responsible for non-immune hydrops fetalis?

Accepted Answer

Parvovirus

Answer

Cytomegalovirus

Answer

Herpes simplex virus

Answer

Hepatitis B virus

Question 9

Which of the following is NOT an oncogenic virus?

Accepted Answer

Herpes simplex virus

Answer

Human papilloma virus

Answer

Epstein-Barr virus

Answer

Hepatitis B virus

Question 10

A child presents with mononucleosis-like symptoms, but the test for mononucleosis and EBV titers are negative. What is a common cause of heterophile-negative mononucleosis?

Accepted Answer

Cytomegalovirus

Answer

Herpes simplex virus

Answer

Varicella-zoster virus

Answer

Adenovirus

Virology — MCQs

Virology — MCQs

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