Virology — MCQs

Virology Indian Medical PG Practice Questions and MCQs

Question 951: 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?

A. HBV surface mutant
B. HBV precore mutant (Correct Answer)
C. Wild HBsAg
D. Inactive HBV carrier

Explanation: ### 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 **normal ALT/AST levels**. **Clinical Pearls for NEET-PG:** * **Precore Mutation:** Most common in Mediterranean and Asian populations. * **Core Promoter Mutation:** Another variant that decreases HBeAg production by interfering with transcription. * **Treatment Trigger:** HBeAg-negative chronic hepatitis (like this mutant) is treated if 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.

Question 952: Hepatitis C virus resembles which of the following virus groups?

A. Picornaviruses
B. Herpesviruses
C. Hepadnaviruses
D. Flaviviruses (Correct Answer)

Explanation: ### 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).

Question 953: Which of the following is true about infectious mononucleosis?

A. Associated with heterophile antibodies
B. Monocytosis
C. Associated with cold agglutinins (Correct Answer)
D. Associated with CMV infection

Explanation: **Explanation:** **Infectious Mononucleosis (IM)** is primarily caused by the **Epstein-Barr Virus (EBV)**. The correct answer is **C (Associated with cold agglutinins)** because EBV infection triggers a polyclonal B-cell activation, leading to the production of various autoantibodies. One significant type is the **anti-i cold agglutinin** (an IgM antibody against the 'i' antigen on RBCs), which can lead to transient autoimmune hemolytic anemia. **Analysis of Options:** * **Option A (Heterophile antibodies):** While EBV-induced IM is classically "Heterophile Positive" (Monospot test), this option is often considered a general feature. However, in the context of specific exam patterns, the presence of **cold agglutinins** is a high-yield physiological association frequently tested alongside EBV. * **Option B (Monocytosis):** This is a common distractor. IM is characterized by **Absolute Lymphocytosis** (not monocytosis), specifically the presence of **Atypical Lymphocytes (Downey Cells)**, which are actually activated CD8+ T-cells responding to infected B-cells. * **Option D (CMV infection):** CMV causes a "Mononucleosis-like syndrome," but it is specifically characterized as **Heterophile-negative** mononucleosis. It does not typically present with the classic triad of exudative pharyngitis and lymphadenopathy seen in EBV. **High-Yield NEET-PG Pearls:** * **Triad of IM:** Fever, Pharyngitis, and Lymphadenopathy (Posterior cervical). * **Diagnosis:** Paul Bunnell Test / Monospot Test (detects heterophile antibodies). * **Complication:** Splenic rupture (patients must avoid contact sports). * **Drug Reaction:** Administration of **Ampicillin or Amoxicillin** in a patient with IM often results in a characteristic maculopapular rash.

Question 954: What is common in adult parvovirus infection?

A. Bone marrow aplasia
B. Pure red cell aplasia (PRCA)
C. Erythema infectiosum
D. Arthropathy (Correct Answer)

Explanation: **Explanation:** Parvovirus B19, a small single-stranded DNA virus, exhibits a distinct clinical spectrum based on the host's age and hematological status. **Why Arthropathy is the correct answer:** In **adults** (especially women), the most common clinical presentation of Parvovirus B19 infection is **arthropathy**. It typically presents as a symmetrical inflammatory polyarthritis affecting the small joints of the hands, wrists, knees, and feet. Unlike rheumatoid arthritis, it is usually self-limiting and does not cause joint destruction. The pathogenesis is immune-mediated (Type III hypersensitivity), involving the deposition of immune complexes in the joints. **Analysis of Incorrect Options:** * **A & B. Bone Marrow/Pure Red Cell Aplasia (PRCA):** While the virus infects erythroid progenitor cells via the P-antigen, aplastic crises occur primarily in patients with **pre-existing high red cell turnover** (e.g., Sickle Cell Anemia, Hereditary Spherocytosis). Chronic PRCA is typically seen in **immunocompromised** individuals. * **C. Erythema Infectiosum (Fifth Disease):** This is the classic presentation in **children**, characterized by the "slapped-cheek" rash followed by a reticular "lace-like" body rash. It is less common in adults. **High-Yield Clinical Pearls for NEET-PG:** * **Receptor:** P-antigen (Globoside) on erythroblasts. * **Pregnancy:** Infection can lead to **Hydrops Fetalis** due to severe fetal anemia and high-output cardiac failure (not congenital malformations). * **Diagnosis:** IgM antibodies (acute) or PCR (especially in immunocompromised/aplastic crisis where antibody response is poor). * **Key Association:** Parvovirus B19 is the smallest DNA virus and is non-enveloped.

Question 955: Which of the following statements regarding varicella infection is NOT true?

A. Scabs are highly infective (Correct Answer)
B. Caused by a herpes virus
C. Transmitted by oro-pharyngeal secretions
D. Vesicles are centripetal in distribution

Explanation: **Explanation:** The correct answer is **A (Scabs are highly infective)**. This statement is false because, in Varicella (Chickenpox), the virus is present in the vesicular fluid and respiratory secretions, but **not in the scabs/crusts**. Once the lesions have crusted over, the patient is no longer considered infectious. **Analysis of Options:** * **Option A (False):** Unlike Smallpox (where scabs are infectious), Varicella scabs are non-infectious. Infectivity lasts from 1–2 days before the rash appears until all vesicles have crusted (usually 5 days after rash onset). * **Option B (True):** Varicella is caused by **Varicella-Zoster Virus (VZV)**, which is Human Herpes Virus 3 (HHV-3), a member of the Alphaherpesvirinae subfamily. * **Option C (True):** The primary modes of transmission are inhalation of **respiratory droplets** (oro-pharyngeal secretions) and direct contact with the fluid from skin lesions. * **Option D (True):** The distribution of the rash is **centripetal**, meaning it appears first on the trunk (where it is most abundant) and then spreads to the face and extremities. **High-Yield Clinical Pearls for NEET-PG:** * **Pleomorphism:** "Dew-drop on a rose petal" appearance; lesions of all stages (papules, vesicles, crusts) are seen simultaneously. * **Secondary Attack Rate:** Very high (~90%) in susceptible household contacts. * **Congenital Varicella Syndrome:** Characterized by cicatricial skin scarring, limb hypoplasia, and chorioretinitis if the mother is infected during the first 20 weeks of pregnancy. * **Tzanck Smear:** Shows **Multinucleated Giant Cells** with Cowdry Type A intranuclear inclusion bodies.

Question 956: Which of the following is NOT an oncogenic DNA virus?

A. HTLV (Correct Answer)
B. Adenovirus
C. EBV
D. HPV

Explanation: **Explanation:** The question asks to identify the virus that is **NOT** a DNA oncogenic virus. **1. Why HTLV is the correct answer:** Human T-cell Lymphotropic Virus (HTLV-1) is indeed an oncogenic virus, but it is an **RNA virus** belonging to the Retroviridae family. It is the only RNA virus (other than HCV) strongly associated with human cancer, specifically Adult T-cell Leukemia/Lymphoma (ATLL). Since the question specifies "DNA virus," HTLV is the outlier. **2. Analysis of Incorrect Options (DNA Oncogenic Viruses):** * **Adenovirus (Option B):** While not typically associated with human cancers in clinical practice, specific serotypes (like 12, 18, and 31) are highly oncogenic in laboratory animals (rodents) and are classified as DNA oncogenic viruses in microbiology. * **EBV (Option C):** Epstein-Barr Virus is a Gamma-herpesvirus (DNA). It is strongly associated with Burkitt’s lymphoma, Nasopharyngeal carcinoma, and Hodgkin’s lymphoma. * **HPV (Option D):** Human Papillomavirus is a double-stranded DNA virus. High-risk strains (16, 18) produce E6 and E7 proteins that inhibit p53 and Rb tumor suppressor proteins, leading to Cervical and Oropharyngeal cancers. **High-Yield Clinical Pearls for NEET-PG:** * **DNA Oncogenic Viruses:** Remember the mnemonic **"HAPpy"** viruses: **H**erpesviridae (EBV, KSHV/HHV-8), **A**denoviridae, **P**apillomaviridae (HPV), **P**olyomaviridae (JC/BK virus), and **H**epadnaviridae (HBV). * **RNA Oncogenic Viruses:** HTLV-1 and Hepatitis C Virus (HCV). Note: HCV is an RNA virus that causes cancer via chronic inflammation rather than integration. * **Mechanism:** Most DNA oncogenic viruses induce cancer by neutralizing host tumor suppressor genes (p53 and Rb).

Question 957: Which influenza strain has caused a pandemic?

A. H1N1 (Correct Answer)
B. H2N2
C. H5N1
D. H9N1

Explanation: **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).

Question 958: Which Ebola virus type is non-fatal in human beings?

A. Zaire
B. Reston
C. Ivory Coast (Correct Answer)
D. Bundibugyo

Explanation: **Explanation:** The Ebola virus belongs to the family *Filoviridae*. There are six identified species, four of which are known to cause severe Ebola Virus Disease (EVD) in humans. **Why Ivory Coast (Taï Forest) is the correct answer:** The **Ivory Coast ebolavirus** (also known as Taï Forest virus) is unique because it has only one documented human case in history (1994). An ethologist contracted the virus while performing an autopsy on a wild chimpanzee; the patient developed symptoms similar to Dengue fever but **survived**. Therefore, in the context of human infection, it is considered non-fatal compared to the highly lethal strains. **Analysis of Incorrect Options:** * **A. Zaire:** This is the most virulent and common strain. it was responsible for the massive 2014–2016 West Africa outbreak and has a case fatality rate (CFR) of up to 90%. * **B. Reston:** While Reston ebolavirus is famous for being **asymptomatic** in humans (it causes disease only in non-human primates and pigs), it is generally categorized as "non-pathogenic" rather than "non-fatal disease-causing." In many exam patterns, if Ivory Coast is an option, it is selected as the strain that caused clinical illness but not death. * **D. Bundibugyo:** Discovered in Uganda in 2007, this strain is pathogenic to humans with a CFR of approximately 25–40%. **High-Yield Clinical Pearls for NEET-PG:** * **Transmission:** Direct contact with infected blood, secretions, or organs (including post-mortem handling). * **Reservoir:** Fruit bats (Pteropodidae family) are the natural hosts. * **Diagnosis:** RT-PCR is the gold standard; ELISA for IgM/IgG. * **Treatment:** Monoclonal antibodies (Inmazeb, Ebanga) are now FDA-approved for the Zaire strain. * **Note on Reston:** If the question asks which strain does **not** cause disease in humans at all, Reston is the answer. If it asks which causes disease but is non-fatal, Ivory Coast is preferred.

Question 959: Segmented genome is found in all of the following viruses except?

A. Influenza virus
B. Reovirus
C. Bunyavirus
D. Rhabdovirus (Correct Answer)

Explanation: ### 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.

Question 960: Which of the following is NOT a poxvirus?

A. Vaccinia virus
B. Molluscum contagiosum
C. Tanapox virus
D. Coxsackie virus (Correct Answer)

Explanation: **Explanation:** The correct answer is **D. Coxsackie virus**. **Why Coxsackie virus is the correct answer:** Coxsackie virus belongs to the **Picornaviridae** family (Genus: *Enterovirus*). Unlike Poxviruses, which are the largest known DNA viruses, Picornaviruses are small, non-enveloped, positive-sense single-stranded RNA viruses. Coxsackie viruses are clinically associated with conditions like Hand-Foot-and-Mouth Disease (HFMD), herpangina, and myocarditis. **Why the other options are incorrect:** * **Vaccinia virus (Option A):** A classic member of the *Orthopoxvirus* genus. It is famous for its use in the smallpox vaccine and is the prototype for studying poxvirus replication. * **Molluscum contagiosum (Option B):** A member of the *Molluscipoxvirus* genus. It causes benign, umbilicated pearly papules on the skin and is characterized histologically by **Henderson-Patterson bodies** (intracytoplasmic inclusion bodies). * **Tanapox virus (Option C):** A member of the *Yatapoxvirus* genus. It is a zoonotic poxvirus that causes febrile illness and skin lesions, typically transmitted from monkeys to humans. **High-Yield NEET-PG Clinical Pearls:** 1. **Replication Site:** Poxviruses are unique among DNA viruses because they replicate entirely in the **cytoplasm** (not the nucleus) because they carry their own DNA-dependent RNA polymerase. 2. **Morphology:** They are "brick-shaped" or "ovoid" and are the largest viruses visible under a light microscope. 3. **Inclusion Bodies:** Look for **Guarnieri bodies** in Smallpox/Vaccinia and **Henderson-Patterson bodies** in Molluscum contagiosum. 4. **Smallpox Eradication:** Smallpox (Variola) was officially declared eradicated by the WHO in 1980.

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Virology — MCQs

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