Virology Practice Questions

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.

Q: Which of the following is a DNA virus?

Adenovirus. **Explanation:** The classification of viruses based on their genetic material is a fundamental concept in virology. Most animal viruses contain either DNA or RNA. **Correct Answer: B. Adenovirus** Adenoviruses are non-enveloped, icosahedral viruses containing **double-stranded DNA (dsDNA)**. They are a classic example of DNA viruses and are clinically significant for causing respiratory tract infections (pharyngoconjunctival fever), epidemic keratoconjunctivitis, and hemorrhagic cystitis. **Analysis of Incorrect Options:** * **A. Poliovirus:** A member of the *Picornaviridae* family, it is a single-stranded, positive-sense RNA (+ssRNA) virus. * **C. Parvovirus:** While Parvovirus B19 is indeed a DNA virus, it is unique because it is **single-stranded DNA (ssDNA)**. In many standardized exams, if a question asks for "the" DNA virus among options containing both dsDNA and ssDNA, the focus is often on the standard dsDNA structure unless "ssDNA" is specified. However, in a strict classification sense, both B and C are DNA viruses. In the context of typical NEET-PG patterns, Adenovirus is the prototypical dsDNA virus. * **D. Hepatitis A virus:** Like Poliovirus, it belongs to the *Picornaviridae* family and contains +ssRNA. **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic for DNA Viruses:** "**HHAPPPPy**" – **H**erpes, **H**epadna, **A**deno, **P**apilloma, **P**olyoma, **P**arvo, and **P**ox. * **Exceptions to remember:** All DNA viruses are double-stranded except **Parvovirus** (ssDNA). All DNA viruses are icosahedral except **Poxvirus** (complex/brick-shaped). * **Replication:** All DNA viruses replicate in the **nucleus**, except **Poxvirus**, which replicates in the cytoplasm (carrying its own DNA-dependent RNA polymerase).

Q: What is the significance of mutation of CCR5 protein?

High resistance to HIV infection. ### Explanation **Core Concept:** HIV-1 primarily enters host CD4+ T-cells by binding to the CD4 receptor and a specific co-receptor. The **CCR5 protein** is a chemokine receptor that serves as the essential co-receptor for **M-tropic (Macrophage-tropic)** strains of HIV, which are responsible for the initial infection and transmission. A specific mutation known as the **CCR5-Δ32 (delta 32) mutation** results in a truncated, non-functional protein that is not expressed on the cell surface. Individuals who are **homozygous** for this mutation lack the "doorway" for the virus to enter, conferring **high resistance to HIV infection**. Heterozygotes typically show a slower progression to AIDS. **Analysis of Options:** * **Option A (Correct):** Without a functional CCR5 co-receptor, the virus cannot fuse with the host cell membrane, preventing infection. * **Option B:** A mutation (specifically Δ32) leads to resistance, not susceptibility, because the virus loses its binding site. * **Option C:** Resistance to ART is usually due to mutations in the viral genome (e.g., Pol gene mutations affecting Reverse Transcriptase or Protease), not host receptor mutations. * **Option D:** Virulence is a viral property; host receptor mutations affect the host's "permissiveness" to infection rather than the inherent pathogenicity of the virus. **High-Yield Clinical Pearls for NEET-PG:** * **CXCR4:** This is the co-receptor for **T-tropic** strains, which usually appear later in the course of the disease (associated with rapid CD4 decline). * **Maraviroc:** A drug that acts as a **CCR5 antagonist**, mimicking the effect of the mutation to prevent viral entry. * **Berlin Patient:** The first person cured of HIV received a bone marrow transplant from a donor homozygous for the CCR5-Δ32 mutation. * **GP120:** The viral envelope protein that initially binds to CD4 and then undergoes a conformational change to bind to CCR5/CXCR4.

Question 1

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 2

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 3

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 4

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 5

Which of the following is NOT caused by Adenovirus?

Accepted Answer

Infectious mononucleosis

Answer

Hemorrhagic cystitis

Answer

Diarrhea

Answer

Respiratory tract infection

Question 6

HHV-6B causes which of the following?

Accepted Answer

Focal encephalitis

Answer

Carcinoma cervix

Answer

Carcinoma endometrium

Answer

Clear cell carcinoma

Question 7

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

Question 8

A latent, measles-like viral infection and, presumably, a defect in cellular immunity is associated with which of the following diseases?

Accepted Answer

Subacute sclerosing panencephalitis (SSPE)

Answer

Progressive multifocal leukoencephalopathy (PML)

Answer

Multiple sclerosis (MS)

Answer

Creutzfeldt-Jakob disease

Question 9

Which of the following is a DNA virus?

Accepted Answer

Adenovirus

Answer

Poliovirus

Answer

Parvovirus

Answer

Hepatitis A virus

Question 10

What is the significance of mutation of CCR5 protein?

Accepted Answer

High resistance to HIV infection

Answer

High susceptibility to HIV infection

Answer

Causes resistance to anti-retroviral therapy

Answer

Causes increased virulence of the virus

Virology — MCQs

Virology — MCQs

On this page

Practice by Chapter

Want unlimited practice?