Virology Practice Questions

Q: A 32-year-old man presents to the emergency room with a severe headache. Nuchal rigidity is found on physical examination. Lumbar puncture demonstrates cerebrospinal fluid with markedly increased lymphocytes and no other increased cell populations. Which of the following agents is the most likely cause of his symptoms?

Herpes virus. ### Explanation The clinical presentation of headache and nuchal rigidity indicates **meningitis**. The key to solving this case lies in the CSF analysis: **markedly increased lymphocytes** with no other cell types (like neutrophils) suggests **Aseptic (Viral) Meningitis**. **1. Why Herpes Virus is Correct:** Viral infections are the most common cause of lymphocytic pleocytosis in the CSF. While Enteroviruses are the most frequent cause of viral meningitis overall, **Herpes Simplex Virus (HSV)**—specifically HSV-2—is a significant cause of aseptic meningitis in adults. In viral meningitis, CSF typically shows normal glucose, normal to slightly elevated protein, and a predominance of lymphocytes. **2. Why the Other Options are Incorrect:** * **A. Escherichia coli & B. Haemophilus influenzae:** These are causes of **Acute Pyogenic (Bacterial) Meningitis**. The CSF profile would show a predominance of **neutrophils** (polymorphonuclear leukocytes), significantly decreased glucose, and markedly elevated protein. * **D. Mycobacterium tuberculosis:** While TB meningitis causes lymphocytic pleocytosis, it is typically associated with a **"cobweb" appearance** of CSF, very high protein levels, and **significantly decreased glucose**. The clinical course is also usually more subacute/chronic rather than an emergency presentation. **3. NEET-PG High-Yield Pearls:** * **HSV-1** is the most common cause of sporadic **Viral Encephalitis** (targeting the temporal lobes). * **HSV-2** is more commonly associated with **Viral Meningitis** (Mollaret’s meningitis). * **CSF Findings Summary:** * *Bacterial:* ↑ Neutrophils, ↓ Glucose, ↑↑ Protein. * *Viral:* ↑ Lymphocytes, Normal Glucose, Normal/↑ Protein. * *Tubercular:* ↑ Lymphocytes, ↓ Glucose, ↑ Protein (Fibrin web).

Q: Which of the following statements regarding Cytomegalovirus (CMV) is FALSE?

Foscarnet can completely eliminate CMV infection.. **Explanation:** The correct answer is **C**, as no current antiviral therapy, including Foscarnet, can completely eliminate Cytomegalovirus (CMV) from the body. **Why Option C is False:** CMV is a member of the *Herpesviridae* family. Like all herpesviruses, CMV establishes **lifelong latency** in the host (specifically in monocytes, macrophages, and CD34+ hematopoietic progenitor cells). Antiviral drugs like Ganciclovir, Foscarnet, and Cidofovir inhibit viral DNA polymerase and stop active replication, but they cannot eradicate the latent viral genome. Therefore, the infection is suppressed, not eliminated. **Analysis of Other Options:** * **Option A:** CMV is indeed a **double-stranded DNA (dsDNA)** virus, belonging to the Beta-herpesvirus subfamily. * **Option B:** In immunocompetent individuals, primary CMV infection is usually asymptomatic or presents as a self-limiting **mononucleosis-like syndrome** (Heterophile antibody negative). * **Option D:** CMV retinitis is an AIDS-defining illness. It typically occurs as an opportunistic infection when the **CD4 count falls below 50–100 cells/mm³**. It is extremely rare in patients with a CD4 count >200 cells/mm³. **High-Yield Clinical Pearls for NEET-PG:** * **Histology:** Look for **"Owl’s Eye" intranuclear inclusion bodies** (large cells with clear halos around the nucleus). * **Congenital CMV:** Most common viral cause of congenital defects; characterized by periventricular calcifications, microcephaly, and sensorineural hearing loss. * **Treatment of Choice:** **Ganciclovir** is the first-line agent. **Foscarnet** is used for ganciclovir-resistant strains but is limited by nephrotoxicity. * **Transplant Medicine:** CMV is the most common viral infection complicating solid organ transplants.

Q: Epstein-Barr virus (EBV) causes which of the following conditions?

Pancreatic carcinoma. **Explanation:** The question asks to identify which condition is **NOT** typically associated with Epstein-Barr Virus (EBV), as Pancreatic carcinoma is the "odd one out" in this clinical context. **1. Why Pancreatic Carcinoma is the Correct Answer (The Exception):** Epstein-Barr Virus (EBV), a γ-herpesvirus (HHV-4), is known for its strong association with various B-cell and epithelial malignancies. However, **Pancreatic carcinoma** has no established causal link with EBV. Pancreatic cancer is primarily associated with smoking, chronic pancreatitis, and mutations in the KRAS, CDKN2A, TP53, and SMAD4 genes, rather than viral oncogenesis. **2. Analysis of Incorrect Options (Associations with EBV):** * **Glandular Fever (Infectious Mononucleosis):** This is the primary clinical manifestation of EBV infection, characterized by the triad of fever, pharyngitis, and lymphadenopathy. It is diagnosed via the Paul-Bunnell test (heterophile antibodies). * **Burkitt’s Lymphoma:** EBV is strongly linked to the African (endemic) variant of Burkitt’s lymphoma, characterized by the **t(8;14)** translocation involving the c-myc oncogene. * **Nasopharyngeal Carcinoma:** This is an epithelial tumor highly prevalent in Southern China, where EBV DNA is consistently found within the tumor cells. **3. High-Yield Clinical Pearls for NEET-PG:** * **Receptor:** EBV binds to the **CD21** receptor (CR2) on B-cells and the MHC class II molecule. * **Hematology:** Peripheral smear shows **Atypical Lymphocytes (Downey cells)**, which are actually activated T-cells (CD8+) reacting against infected B-cells. * **Other Associations:** Oral Hairy Leukoplakia (in HIV patients), Hodgkin’s Lymphoma (Mixed cellularity subtype), and Gastric Carcinoma (approx. 10% of cases). * **Diagnosis:** Monospot test is the screening test of choice; VCA-IgM (Viral Capsid Antigen) indicates acute infection.

Q: All of the following are caused by RNA viruses, EXCEPT:

Fifth disease. **Explanation:** The core concept tested here is the classification of viruses based on their genetic material. **Correct Answer: D. Fifth Disease** Fifth disease (also known as Erythema Infectiosum) is caused by **Parvovirus B19**. Parvovirus is a **DNA virus**. Specifically, it is unique for being a **non-enveloped, single-stranded DNA (ssDNA)** virus. In the NEET-PG context, remembering that "Parvo" is the only medically significant ssDNA virus is a high-yield fact. **Why the other options are incorrect:** * **A. HIV:** This is a Retrovirus. It contains two copies of single-stranded **RNA** (ssRNA) and uses reverse transcriptase to integrate into the host genome. * **B. Dengue:** Caused by the Dengue virus, which belongs to the *Flaviviridae* family. All Flaviviruses are enveloped, positive-sense **ssRNA** viruses. * **C. Herpangina:** Despite the name sounding like "Herpes" (which is DNA), Herpangina is caused by **Coxsackievirus A**, a member of the *Picornaviridae* family. All Picornaviruses are non-enveloped **ssRNA** viruses. **Clinical Pearls for NEET-PG:** 1. **Fifth Disease Presentation:** Characterized by the "slapped-cheek" rash and can cause aplastic crisis in patients with sickle cell anemia or hereditary spherocytosis. 2. **DNA Virus Mnemonic:** Remember **"HHAPPPPy"** viruses (Herpes, Hepadna, Adeno, Papilloma, Polyoma, Pox, Parvo). All are double-stranded except Parvo (ssDNA). 3. **Herpangina vs. Herpes:** Herpangina (Coxsackie) typically causes vesicles on the **posterior** pharynx/soft palate, whereas Herpetic Gingivostomatitis (HSV-1) involves the **anterior** mouth and gums.

Q: Which one of the following is a double-stranded RNA virus?

Reovirus. **Explanation:** The correct answer is **Reovirus**. In virology, the majority of RNA viruses are single-stranded (ssRNA). **Reoviruses** (which include **Rotavirus**) are the notable exception, characterized by a **segmented, double-stranded RNA (dsRNA)** genome and a double-layered icosahedral capsid. **Why the other options are incorrect:** * **Hepatitis A (Picornavirus):** This is a non-enveloped, **positive-sense single-stranded RNA (+ssRNA)** virus. It is primarily transmitted via the fecal-oral route. * **Hepatitis E (Hepevirus):** Similar to Hepatitis A, it is a non-enveloped **+ssRNA** virus. It is significant in pregnancy due to the high risk of fulminant hepatic failure. * **Coronavirus:** These are enveloped, **+ssRNA** viruses. They possess the largest genomes among RNA viruses and are known for their characteristic "club-shaped" surface projections (peplomers). **High-Yield Clinical Pearls for NEET-PG:** 1. **Mnemonic for dsRNA:** Remember **"REO"** – **R**espiratory **E**nteric **O**rphan. 2. **Rotavirus:** A member of the Reoviridae family, it is the most common cause of severe infantile diarrhea worldwide. It features **11 segments** of dsRNA. 3. **Wheel-like appearance:** Under electron microscopy, Rotavirus exhibits a characteristic "wheel-and-spoke" appearance (Latin *rota* means wheel). 4. **Segmented Genomes:** Other segmented RNA viruses include **B**unyavirus, **O**rthomyxovirus (Influenza), and **A**renavirus (Mnemonic: **BOAR**). Only Reovirus among these is double-stranded.

Q: Which of the following is a marker of acute hepatitis B infection?

DNA polymerase. **Explanation:** The presence of **DNA polymerase** is a direct indicator of active viral replication. In Hepatitis B (HBV), DNA polymerase is found within the core of the virus; its detection in the serum occurs during the early phase of acute infection, coinciding with the peak of viral load and infectivity. While HBsAg is the most common screening marker, DNA polymerase (and HBV DNA) serves as a highly specific marker for the replicative phase of acute hepatitis. **Analysis of Options:** * **Hepatitis core antigen (HBcAg):** This is a "sequestrated" antigen. It is found inside the hepatocyte but **does not circulate freely in the blood**. Therefore, it cannot be used as a serum marker for diagnosis. * **Anti-HBs:** These are protective antibodies that appear after the disappearance of HBsAg. They indicate **recovery and immunity** (either from past infection or vaccination), not an acute infection. * **IgG to core antigen (Anti-HBc IgG):** This marker indicates a **past or chronic infection**. In acute infection, the predominant antibody to the core antigen is of the **IgM** class. **Clinical Pearls for NEET-PG:** * **First marker to appear:** HBsAg. * **Marker of infectivity:** HBeAg and HBV DNA (DNA polymerase). * **Window Period marker:** Anti-HBc IgM (HBsAg and Anti-HBs are both negative). * **Best indicator of vaccination:** Anti-HBs (with all other markers negative). * **Only marker present in all phases of infection (except vaccination):** Anti-HBc (Total).

Q: What is the sequence of genetic material replication followed by a retrovirus upon entering a host cell?

RNA to DNA to RNA. **Explanation:** The hallmark of a **Retrovirus** (e.g., HIV, HTLV) is its ability to reverse the normal flow of genetic information (Central Dogma). 1. **Why Option A is Correct:** Upon entering the host cell, the retrovirus releases its single-stranded positive-sense **RNA** genome. The viral enzyme **Reverse Transcriptase** (RNA-dependent DNA polymerase) converts this RNA into double-stranded **DNA**. This DNA (provirus) integrates into the host genome. Finally, the host’s cellular machinery transcribes this integrated DNA back into new viral **RNA** (genomic RNA and mRNA for protein synthesis). Thus, the sequence is **RNA → DNA → RNA**. 2. **Why Other Options are Incorrect:** * **Option B (RNA to DNA):** This is only the first half of the cycle (Reverse Transcription). Without the final step of transcribing DNA back to RNA, new virions cannot be assembled. * **Option C (DNA to RNA):** This is the standard "Central Dogma" followed by DNA viruses (e.g., Herpesvirus) and host cells, not retroviruses. * **Option D (DNA to RNA to DNA):** This is the replication cycle of **Hepadnaviruses** (e.g., Hepatitis B). They contain a DNA genome, use an RNA intermediate (pre-genome), and use reverse transcriptase to go back to DNA. **High-Yield Clinical Pearls for NEET-PG:** * **Reverse Transcriptase** has three activities: RNA-dependent DNA polymerase, RNase H (degrades the original RNA template), and DNA-dependent DNA polymerase. * **Integrase** is the enzyme responsible for incorporating viral DNA into the host chromosome. * **Hepatitis B** is the only DNA virus that utilizes reverse transcriptase, but its sequence is DNA → RNA → DNA.

Question 1

A 32-year-old man presents to the emergency room with a severe headache. Nuchal rigidity is found on physical examination. Lumbar puncture demonstrates cerebrospinal fluid with markedly increased lymphocytes and no other increased cell populations. Which of the following agents is the most likely cause of his symptoms?

Accepted Answer

Herpes virus

Answer

Escherichia coli

Answer

Haemophilus influenzae

Answer

Mycobacterium tuberculosis

Question 2

Which virus spreads by both hematogenous and neural routes?

Accepted Answer

Poliovirus

Answer

Rabies virus

Answer

Varicella zoster virus

Answer

Epstein-Barr virus

Question 3

Which of the following statements regarding Cytomegalovirus (CMV) is FALSE?

Accepted Answer

Foscarnet can completely eliminate CMV infection.

Answer

CMV is a double-stranded DNA virus.

Answer

CMV rarely causes significant problems in immunocompetent individuals.

Answer

CMV retinitis is rare when the CD4 count is greater than 200 cells/mm³.

Question 4

Epstein-Barr virus (EBV) causes which of the following conditions?

Accepted Answer

Pancreatic carcinoma

Answer

Glandular fever

Answer

Burkitt's lymphoma

Answer

Nasopharyngeal carcinoma

Question 5

All of the following are caused by RNA viruses, EXCEPT:

Accepted Answer

Fifth disease

Answer

HIV

Answer

Dengue

Answer

Herpangina

Question 6

An elderly male presents with fever, cough, and shortness of breath for 2 weeks. He has a history of chronic bronchitis and diabetes, and recent travel to Wuhan City, China. What is the symmetry of the causative virus?

Accepted Answer

Enveloped helical symmetry

Answer

Naked helical symmetry

Answer

Complex symmetry

Answer

Icosahedral symmetry

Question 7

Which one of the following is a double-stranded RNA virus?

Accepted Answer

Reovirus

Answer

Hepatitis A

Answer

Hepatitis E

Answer

Coronavirus

Question 8

Which of the following is a marker of acute hepatitis B infection?

Accepted Answer

DNA polymerase

Answer

Hepatitis core antigen

Answer

Anti HBs

Answer

IgG to core antigen

Question 9

What is the sequence of genetic material replication followed by a retrovirus upon entering a host cell?

Accepted Answer

RNA to DNA to RNA

Answer

RNA to DNA

Answer

DNA to RNA

Answer

DNA to RNA to DNA

Question 10

All the following statements are true for the viral genome in HIV, except?

Accepted Answer

They consist of DNA dependent DNA polymerase activity

Answer

They are diploid

Answer

They consist of three major genes-gag, pol and env characteristic of all retroviruses

Answer

They are the most complex of human retroviruses

Virology — MCQs

Virology — MCQs

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