Virology Practice Questions

Q: Infectivity of Hepatitis B virus is best diagnosed by which marker?

HBeAg. **Explanation:** The infectivity of Hepatitis B Virus (HBV) is primarily determined by the rate of viral replication. **1. Why HBeAg is the correct answer:** **HBeAg (Hepatitis B e-antigen)** is a soluble protein produced during active viral replication. Its presence in the serum serves as a surrogate marker for high viral load and **maximal infectivity**. Clinically, if a patient is HBeAg-positive, they are considered highly infectious (e.g., a high risk of vertical transmission from mother to child). While HBV DNA is a more precise quantitative measure, HBeAg remains the classic diagnostic marker for assessing infectivity in standard examinations. **2. Why other options are incorrect:** * **HBsAg:** This is the first marker to appear and indicates **active infection** (either acute or chronic). However, it does not differentiate between high and low replication states; thus, it is a marker of "infection," not "infectivity." * **HBV DNA:** This is the most sensitive marker for viral replication and is used to monitor treatment. While it correlates with infectivity, in the context of standard MCQ patterns, HBeAg is the established "diagnostic marker" for infectivity. * **Anti-HBsAg:** These are protective antibodies that appear after the disappearance of HBsAg. They indicate **immunity** (via vaccination or recovery) and imply zero infectivity. **High-Yield Clinical Pearls for NEET-PG:** * **Window Period:** The interval where HBsAg and Anti-HBs are both negative; **Anti-HBc IgM** is the only marker present. * **Pre-core Mutant:** A condition where the patient is HBeAg negative but has high HBV DNA levels and high infectivity. * **Best marker of vaccination response:** Anti-HBs titers (>10 mIU/mL). * **First marker to appear:** HBsAg.

Q: Which of the following is not an RNA virus?

Hepatitis B. **Explanation:** The classification of Hepatitis viruses is a high-yield topic for NEET-PG. The correct answer is **Hepatitis B**, as it is the only member of the Hepatitis group that is a **DNA virus**. **1. Why Hepatitis B is the correct answer:** Hepatitis B virus (HBV) belongs to the **Hepadnaviridae** family. It possesses a **partially double-stranded circular DNA** genome. It is unique because it uses an enzyme called **reverse transcriptase** during its replication cycle to convert RNA back into DNA, a feature it shares with retroviruses. **2. Why the other options are incorrect:** * **Hepatitis A (Option A):** A member of the *Picornaviridae* family. It is a non-enveloped, **positive-sense single-stranded RNA (+ssRNA)** virus. * **Hepatitis C (Option C):** A member of the *Flaviviridae* family. It is an enveloped, **+ssRNA** virus. * **Hepatitis D (Option D):** Also known as the "Delta agent," it is a defective **ssRNA** virus that requires the HBsAg (Hepatitis B surface antigen) coat to replicate and cause infection. **Clinical Pearls for NEET-PG:** * **Mnemonic:** All Hepatitis viruses are RNA, **except B** (B = **B**oth strands of DNA, though partially). * **Transmission:** Hepatitis **A** and **E** are transmitted via the **Fecal-Oral** route (Vowels hit the bowels). Hepatitis **B, C, and D** are transmitted parenterally (Blood/Body fluids). * **Hepatitis E:** While it is an RNA virus (*Hepeviridae*), remember it is particularly associated with high mortality in **pregnant women** (fulminant hepatic failure). * **Hepatitis C:** Most common cause of post-transfusion hepatitis and chronic liver disease (cirrhosis/HCC) worldwide.

Q: Which of the following serum markers indicate a super carrier of Hepatitis B Virus (HBV)?

HBsAg + HBeAg + HBV DNA. ### Explanation The term **"Super Carrier"** in Hepatitis B refers to a chronic carrier who is highly infectious. To understand this, we must differentiate between simple carriage and high-level replication. **1. Why Option C is Correct:** A "Super Carrier" is characterized by the presence of three key markers: * **HBsAg (Hepatitis B Surface Antigen):** Indicates the presence of the virus (Chronic state if >6 months). * **HBeAg (Hepatitis B e-Antigen):** This is the hallmark of **active viral replication** and high infectivity. * **HBV DNA:** High levels of viral load in the serum confirm that the virus is actively multiplying. The combination of these three markers signifies that the individual has a high viral load and is most likely to transmit the infection to others (e.g., via needle-stick injuries or vertical transmission). **2. Why Other Options are Incorrect:** * **Option A (HBsAg):** This only indicates that the person is a carrier. It does not specify the level of infectivity or replication. * **Option B (HBsAg + HBV DNA):** While this shows the virus is present and replicating, the absence of **HBeAg** means it doesn't fulfill the classic definition of a "super carrier," as HBeAg is the primary clinical marker for high infectivity. * **Option D (Anti-HBsAg + HBV DNA):** This is a contradictory profile. Anti-HBs indicates immunity/recovery, which usually does not coexist with active HBV DNA (except in rare escape mutants). **3. NEET-PG High-Yield Pearls:** * **Window Period Marker:** Anti-HBc IgM is the only positive marker. * **Best Indicator of Prognosis:** HBV DNA levels. * **Marker of Recovery/Immunity:** Anti-HBs. * **Low Infectivity Carrier:** HBsAg positive but **Anti-HBe** positive (indicates replication has slowed down). * **Pre-core Mutants:** These patients are HBeAg negative but still have high HBV DNA and high infectivity.

Q: Hepatitis C virus (HCV) is classified as which of the following?

Enveloped RNA virus. **Explanation:** Hepatitis C Virus (HCV) belongs to the genus *Hepacivirus* within the **Flaviviridae** family. It is characterized as a small, **enveloped**, **single-stranded, positive-sense RNA virus**. 1. **Why Option A is correct:** HCV possesses a lipid envelope derived from the host cell membrane, which contains glycoproteins (E1 and E2) essential for viral entry. Its genetic material is RNA, specifically positive-sense, meaning it can be directly translated into viral proteins by host ribosomes. 2. **Why Options B and C are incorrect:** These options suggest HCV is non-enveloped. Non-enveloped RNA hepatitis viruses include Hepatitis A (HAV) and Hepatitis E (HEV). These are typically transmitted via the fecal-oral route, whereas enveloped viruses like HCV are more fragile and require parenteral transmission (blood/body fluids). 3. **Why Option D is incorrect:** While HCV is enveloped, it is a **positive-strand** RNA virus. Negative-strand RNA viruses (like Influenza or Rabies) must carry their own RNA-dependent RNA polymerase to transcribe a positive strand before translation can occur. **High-Yield Clinical Pearls for NEET-PG:** * **Transmission:** Primarily parenteral (IV drug use is the most common risk factor). * **Chronicity:** HCV has the highest rate of progression to chronic infection (~75-85%) among hepatitis viruses. * **Genotypes:** Genotype 1 is the most common globally; Genotype 3 is highly prevalent in India. * **Diagnosis:** Screening is done via Anti-HCV antibodies; confirmation requires **HCV-RNA PCR** (Gold Standard). * **Treatment:** Managed with Direct-Acting Antivirals (DAAs) like Sofosbuvir, which target non-structural proteins (NS3/4A, NS5A, NS5B).

Q: Fever and hemorrhagic rash are seen in all of the following viral infections EXCEPT:

Sand fly fever. **Explanation:** The question tests the ability to differentiate between **Viral Hemorrhagic Fevers (VHFs)** and self-limiting febrile illnesses. **1. Why Sandfly Fever is the correct answer:** Sandfly fever (also known as Pappataci fever), caused by the *Phlebovirus* (transmitted by *Phlebotomus papatasi*), is a self-limiting, influenza-like illness. While it presents with sudden onset high fever, severe retro-orbital pain, and conjunctival injection, it is **not** associated with a hemorrhagic rash or bleeding manifestations. It typically resolves within 3–4 days without major complications. **2. Analysis of Incorrect Options:** * **Dengue Fever:** Caused by the *Flavivirus*, it is a classic cause of hemorrhagic manifestations. Severe forms (Dengue Hemorrhagic Fever) present with thrombocytopenia, petechiae, ecchymosis, and gastrointestinal bleeding. * **Lassa Fever:** An Arenavirus endemic to West Africa. It is a notorious cause of VHF, characterized by multi-organ failure, mucosal bleeding, and a high fatality rate. * **Rift Valley Fever:** Like Sandfly fever, it is a *Phlebovirus*, but unlike Sandfly fever, it can progress to severe disease including ocular disease, encephalitis, and a fatal hemorrhagic syndrome with jaundice and hematemesis. **Clinical Pearls for NEET-PG:** * **VHF Families:** Remember the four main families: *Flaviviridae* (Dengue, Yellow Fever), *Filoviridae* (Ebola, Marburg), *Arenaviridae* (Lassa), and *Bunyaviridae* (Crimean-Congo, Rift Valley). * **Sandfly Fever Key Sign:** **Pick’s Sign** (deep erythema of the conjunctivae and face) is a characteristic finding, but it is not a hemorrhagic rash. * **Vector Check:** Sandfly is the vector for both Leishmaniasis (Protozoa) and Sandfly fever (Virus).

Q: Which of the following is NOT caused by Adenovirus?

Infectious mononucleosis. **Explanation:** **Infectious mononucleosis** is the correct answer because it is caused by the **Epstein-Barr Virus (EBV)**, a member of the Herpesviridae family, not Adenovirus. It is clinically characterized by the triad of fever, pharyngitis, and lymphadenopathy, often accompanied by atypical lymphocytosis (Downey cells). **Why the other options are incorrect:** Adenoviruses are non-enveloped, double-stranded DNA viruses known for their diverse tissue tropism, affecting the respiratory, ocular, urinary, and gastrointestinal tracts: * **Hemorrhagic cystitis:** Adenovirus types **11 and 21** are classic causes of acute hemorrhagic cystitis, particularly in children and immunocompromised patients. * **Diarrhea:** Adenovirus types **40 and 41** (subgenus F) are significant causes of infantile gastroenteritis. These are "fastidious" strains that do not grow in routine cell cultures. * **Respiratory tract infection:** This is the most common presentation. Types 1-7 are frequently implicated in pharyngitis, pneumonia, and **Pharyngoconjunctival fever** (often associated with swimming pools). **High-Yield Clinical Pearls for NEET-PG:** * **Structure:** Icosahedral symmetry with characteristic **fibers (pentons)** projecting from the vertices, which act as hemagglutinins and mediate attachment. * **Intranuclear Inclusions:** Produces prominent "smudge cells" (basophilic intranuclear inclusions). * **Military Importance:** Types 4 and 7 are associated with outbreaks of Acute Respiratory Disease (ARD) in military recruits; a live oral vaccine is used in this specific population. * **Keratoconjunctivitis:** Types 8, 19, and 37 cause "Shipyard eye" (Epidemic keratoconjunctivitis).

Q: HHV-6B causes which of the following?

Focal encephalitis. **Explanation:** Human Herpesvirus 6 (HHV-6), specifically the **HHV-6B** variant, is a ubiquitous beta-herpesvirus. While it is primarily known as the causative agent of **Exanthema Subitum (Roseola Infantum)** in children, it is highly neurotropic. In immunocompromised individuals—particularly hematopoietic stem cell transplant (HSCT) recipients—HHV-6B reactivation frequently targets the central nervous system, leading to **limbic encephalitis** or **focal encephalitis**. This typically presents with memory loss, seizures, and focal temporal lobe involvement on MRI, making it a critical differential for neurological decline in transplant patients. **Analysis of Incorrect Options:** * **Options A & B (Carcinoma Cervix & Endometrium):** These are primarily associated with High-Risk **Human Papillomavirus (HPV)** types 16 and 18. HHV-6 has no established causal link with gynecological malignancies. * **Option C (Clear Cell Carcinoma):** This malignancy (often of the kidney or ovary) is associated with genetic mutations (e.g., VHL gene) or endometriosis, not viral infections like HHV-6. **High-Yield Clinical Pearls for NEET-PG:** * **HHV-6 Variants:** HHV-6B causes Roseola; HHV-6A is more common in neuroinflammatory diseases like Multiple Sclerosis (though the link is still being studied). * **Roseola Infantum:** Characterized by high fever for 3–5 days, followed by the sudden appearance of a maculopapular rash as the fever subsides ("Fever falls, rash appears"). * **Drug Association:** HHV-6 reactivation is strongly linked to **DRESS syndrome** (Drug Reaction with Eosinophilia and Systemic Symptoms). * **Treatment:** Ganciclovir or Foscarnet are the preferred agents for severe HHV-6 infections.

Q: Which of the following is the causative agent of a variety of cutaneous warts (plantar, common, and flat) and is associated with cervical neoplasia?

Human papillomavirus. **Explanation:** **Human Papillomavirus (HPV)** is the correct answer as it is a small, non-enveloped DNA virus with a specific tropism for squamous epithelium. It is the primary causative agent for various types of cutaneous warts: * **Plantar warts:** HPV-1 * **Common warts (Verruca vulgaris):** HPV-2 and HPV-4 * **Flat warts:** HPV-3 and HPV-10 Furthermore, high-risk genotypes (specifically **HPV-16 and 18**) are the leading cause of **cervical neoplasia** and carcinoma. They produce E6 and E7 oncoproteins, which inhibit tumor suppressor proteins p53 and pRb, respectively, leading to malignant transformation. **Incorrect Options:** * **West Nile Virus:** A member of the *Flaviviridae* family, transmitted by *Culex* mosquitoes. It typically causes West Nile fever or neuroinvasive diseases like encephalitis, not cutaneous warts or cervical cancer. * **Tick-borne Encephalitis Virus:** Also a Flavivirus, transmitted by *Ixodes* ticks. It primarily affects the central nervous system. * **Polyomavirus:** While related to Papillomaviruses, the most clinically significant human polyomaviruses are BK virus (hemorrhagic cystitis/nephropathy) and JC virus (Progressive Multifocal Leukoencephalopathy). **High-Yield Clinical Pearls for NEET-PG:** * **Koilocytes:** Pathognomonic finding on Pap smear (cells with perinuclear halo and wrinkled "raisinoid" nuclei). * **Vaccination:** Quadrivalent vaccine (Gardasil) covers types 6, 11 (genital warts/condyloma acuminata) and 16, 18 (cervical cancer). * **Epidermodysplasia Verruciformis:** A rare genetic condition associated with HPV-5 and HPV-8, leading to widespread warts and skin cancer.

Question 1

Infectivity of Hepatitis B virus is best diagnosed by which marker?

Accepted Answer

HBeAg

Answer

HBsAg

Answer

HBV DNA

Answer

Anti-HBsAg

Question 2

Which of the following is not an RNA virus?

Accepted Answer

Hepatitis B

Answer

Hepatitis A

Answer

Hepatitis C

Answer

Hepatitis D

Question 3

Which of the following serum markers indicate a super carrier of Hepatitis B Virus (HBV)?

Accepted Answer

HBsAg + HBeAg + HBV DNA

Answer

HBsAg

Answer

HBsAg + HBV DNA

Answer

Anti-HBsAg + HBV DNA

Question 4

Hepatitis C virus (HCV) is classified as which of the following?

Accepted Answer

Enveloped RNA virus

Answer

Nonenveloped RNA virus

Answer

Nonenveloped positive strand RNA virus

Answer

Enveloped negative strand RNA virus

Question 5

Fever and hemorrhagic rash are seen in all of the following viral infections EXCEPT:

Accepted Answer

Sand fly fever

Answer

Dengue fever

Answer

Lassa fever

Answer

Rift Valley fever

Question 6

All of the following are true about poliovirus, except -

Accepted Answer

Type I is responsible for vaccine-associated paralytic poliomyelitis

Answer

Type I is responsible for most epidemics

Answer

Type I is very difficult to eliminate

Answer

Type I is most commonly associated with paralysis

Question 7

Which of the following statements is true about bacteriophages?

Accepted Answer

It imparts toxigenicity to bacteria.

Answer

It is a bacterium.

Answer

It helps in transformation.

Answer

It transfers only chromosomal genes.

Question 8

Which of the following is NOT caused by Adenovirus?

Accepted Answer

Infectious mononucleosis

Answer

Hemorrhagic cystitis

Answer

Diarrhea

Answer

Respiratory tract infection

Question 9

HHV-6B causes which of the following?

Accepted Answer

Focal encephalitis

Answer

Carcinoma cervix

Answer

Carcinoma endometrium

Answer

Clear cell carcinoma

Question 10

Which of the following is the causative agent of a variety of cutaneous warts (plantar, common, and flat) and is associated with cervical neoplasia?

Accepted Answer

Human papillomavirus

Answer

West Nile virus

Answer

Tick-borne encephalitis virus

Answer

Polyomavirus

Virology — MCQs

Virology — MCQs

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