Virology Practice Questions

Q: A child with agammaglobulinemia presents with respiratory tract infection and diarrhea. What is the most likely infectious agent?

Rotavirus. **Explanation:** In patients with **X-linked Agammaglobulinemia (Bruton’s)**, there is a profound deficiency of B-cells and all classes of immunoglobulins (IgG, IgA, IgM). The lack of **Secretory IgA** at mucosal surfaces makes these children highly susceptible to specific gastrointestinal and respiratory pathogens. 1. **Why Rotavirus is correct:** While these patients are classically associated with *Giardia lamblia* (due to lack of IgA), **Rotavirus** is the most common viral cause of severe diarrhea in children with agammaglobulinemia. In the absence of neutralizing antibodies, viral clearance is impaired, leading to prolonged and severe gastroenteritis. 2. **Why other options are incorrect:** * **Coxsackievirus:** While patients with agammaglobulinemia are uniquely susceptible to **Enteroviruses** (like Polio, Echovirus, and Coxsackie), these typically manifest as chronic progressive **meningoencephalitis** or dermatomyositis-like syndromes rather than isolated diarrhea. * **Shigella:** This is an invasive bacterial pathogen. While humoral immunity plays a role, the primary defect in agammaglobulinemia predisposes more significantly to encapsulated bacteria (like *S. pneumoniae* and *H. influenzae*) and specific protozoa/viruses rather than typical bacillary dysentery. **High-Yield Clinical Pearls for NEET-PG:** * **Classic Triad:** Absent B-cells (CD19/20+), absent tonsils/lymph nodes, and recurrent pyogenic infections after 6 months of age (once maternal IgG wanes). * **Most common GI parasite:** *Giardia lamblia*. * **Most common CNS complication:** Chronic Enteroviral Encephalitis. * **Contraindication:** Live vaccines (OPV, Rotavirus vaccine, MMR) are strictly contraindicated. * **Treatment:** Intravenous Immunoglobulin (IVIG) replacement.

Q: A virus produces neonatal infections and infections in immunocompromised patients such as AIDS patients. The most common clinical presentation involves floaters, visual field deficits, and painless loss of vision. It can also produce encephalitis and may cause calcifying lesions in the CNS. What is this virus most likely?

Cytomegalovirus (CMV). ### Explanation The clinical presentation described is classic for **Cytomegalovirus (CMV)**, a member of the Beta-herpesvirinae family. **Why CMV is the correct answer:** 1. **Ocular Involvement:** CMV retinitis is the most common opportunistic ocular infection in AIDS patients (typically when CD4 <50 cells/mm³). It presents with **painless vision loss**, floaters, and a characteristic "pizza-pie" appearance (hemorrhage and exudates) on fundoscopy. 2. **Congenital Infection:** CMV is the most common cause of congenital viral infection. Key features include **periventricular calcifications**, microcephaly, and sensorineural hearing loss. 3. **Immunocompromised State:** In addition to retinitis, it causes esophagitis (linear ulcers) and encephalitis in late-stage HIV. **Why other options are incorrect:** * **EBV:** Primarily associated with Infectious Mononucleosis, Oral Hairy Leukoplakia, and malignancies (Burkitt lymphoma, Nasopharyngeal carcinoma). It does not typically cause retinitis or CNS calcifications. * **HSV:** HSV-1 causes sporadic encephalitis (targeting the **temporal lobes**), but it does not cause periventricular calcifications. Neonatal HSV usually presents with skin-eye-mouth lesions or disseminated disease. * **HIV:** While HIV causes the underlying immunosuppression, the specific triad of retinitis, neonatal calcifications, and opportunistic CNS lesions points directly to the secondary pathogen, CMV. **High-Yield Clinical Pearls for NEET-PG:** * **Histology:** "Owl’s eye" intranuclear inclusion bodies. * **Congenital CMV:** Periventricular calcifications (vs. Toxoplasmosis, which shows diffuse/scattered calcifications). * **Drug of Choice:** Ganciclovir (Valganciclovir for prophylaxis). * **Culture:** Human fibroblast cell lines are used for isolation.

Q: Which of the following is associated with nasopharyngeal cancer?

Human Herpesvirus 4 (HHV-4). **Explanation:** The correct answer is **Human Herpesvirus 4 (HHV-4)**, commonly known as the **Epstein-Barr Virus (EBV)**. EBV is a potent oncogenic virus that infects B-lymphocytes and epithelial cells. Its association with **Nasopharyngeal Carcinoma (NPC)** is well-established, particularly the undifferentiated type (WHO Type III). The virus enters epithelial cells via the CD21 receptor (or through fusion) and establishes latency. Viral proteins, specifically **LMP-1 (Latent Membrane Protein 1)**, act as oncogenes by mimicking CD40 signaling, leading to cell proliferation and inhibition of apoptosis. **Analysis of Incorrect Options:** * **HHV-1 (Herpes Simplex Virus-1):** Primarily associated with orofacial lesions (herpes labialis), gingivostomatitis, and sporadic viral encephalitis. It is not oncogenic. * **HHV-2 (Herpes Simplex Virus-2):** Primarily causes genital herpes and neonatal herpes. While once studied for a link to cervical cancer, Human Papillomavirus (HPV) is the actual causative agent. * **HHV-3 (Varicella-Zoster Virus):** Causes chickenpox (primary infection) and shingles (reactivation). It does not have any known association with malignancy. **High-Yield Clinical Pearls for NEET-PG:** * **EBV-Associated Malignancies:** Apart from NPC, EBV is linked to **Burkitt Lymphoma** (starry-sky appearance, t(8;14)), Hodgkin Lymphoma (Mixed cellularity type), and Primary CNS Lymphoma in AIDS patients. * **Diagnostic Marker:** Elevated titers of **IgA antibodies against EBV Viral Capsid Antigen (VCA)** are used for screening and monitoring recurrence in NPC patients. * **Other Oncogenic Viruses:** Remember HHV-8 is associated with **Kaposi Sarcoma**, and HPV 16/18 are linked to cervical and oropharyngeal cancers.

Q: Fatal familial insomnia is associated with which type of disease?

Prion disease. **Explanation:** **Fatal Familial Insomnia (FFI)** is a rare, autosomal dominant inherited disorder caused by a mutation in the **PRNP gene** (specifically at codon 178). This mutation leads to the misfolding of the normal cellular prion protein ($PrP^C$) into an abnormal, protease-resistant isoform ($PrP^{Sc}$). These prions accumulate primarily in the **thalamus**, leading to neuronal loss and gliosis. * **Why Option A is correct:** FFI belongs to the group of **Transmissible Spongiform Encephalopathies (TSEs)** or Prion diseases. It is characterized clinically by progressive insomnia, autonomic dysfunction (tachycardia, hyperhidrosis), and motor signs, eventually leading to death. * **Why Options B, C, and D are incorrect:** While FFI involves neurodegeneration, it is specifically classified by its unique **proteinaceous infectious** etiology (Prions). It is not caused by uncontrolled cell growth (Neoplastic), ischemia/hemorrhage (Vascular), or standard age-related wear-and-tear (Degeneration) in the absence of prion proteins. **High-Yield Clinical Pearls for NEET-PG:** * **Prion Characteristics:** They are devoid of nucleic acids and resistant to standard sterilization (autoclaving at 121°C). They require **134°C for 1 hour** or 1N NaOH for disinfection. * **The "178/129" Rule:** FFI occurs when there is a mutation at **Codon 178** combined with **Methionine** at Codon 129. If Valine is present at Codon 129 with the same 178 mutation, it results in **Creutzfeldt-Jakob Disease (CJD)**. * **Other Prion Diseases:** Kuru (associated with cannibalism), Gerstmann-Sträussler-Scheinker (GSS) syndrome, and Bovine Spongiform Encephalopathy (Mad Cow Disease).

Q: Elevated IgG and IgM antibody titers to parvovirus suggest a diagnosis of which one of the following?

Fifth disease. **Explanation:** The presence of elevated **IgM and IgG antibodies** to Parvovirus B19 is diagnostic of a recent or ongoing infection. In clinical practice, IgM appears within 10 days of exposure and persists for 2–3 months, indicating an **acute infection**, while IgG appears shortly after and provides lifelong immunity. **Why Fifth Disease is correct:** Parvovirus B19 is the causative agent of **Fifth disease** (Erythema Infectiosum). It typically presents in children with a characteristic "slapped-cheek" rash followed by a reticular (lace-like) rash on the trunk and limbs. The virus targets **erythroid progenitor cells** by binding to the **P-antigen** (globoside) on the cell surface. **Analysis of Incorrect Options:** * **A. Acute Lyme Disease:** Caused by the spirochete *Borrelia burgdorferi*. Diagnosis is based on clinical findings (Erythema migrans) and serology for Borrelia, not Parvovirus. * **C. Hepatitis B Infection:** Caused by the Hepatitis B virus (HBV). Diagnosis relies on markers like HBsAg, anti-HBc IgM, and HBV DNA. * **D. Subacute Sclerosing Panencephalitis (SSPE):** A rare, progressive neurological complication caused by a persistent **Measles virus** infection, characterized by high titers of anti-measles antibodies in the CSF and serum. **High-Yield Clinical Pearls for NEET-PG:** * **Aplastic Crisis:** Parvovirus B19 can cause a transient cessation of erythropoiesis, which is life-threatening in patients with high red cell turnover (e.g., **Sickle Cell Anemia**, Hereditary Spherocytosis). * **Hydrops Fetalis:** Infection during pregnancy can lead to severe fetal anemia, high-output cardiac failure, and fetal death. * **Arthropathy:** In adults, infection often presents as symmetrical small joint arthritis (mimicking Rheumatoid Arthritis). * **Receptor:** The cellular receptor for Parvovirus B19 is the **P-antigen**.

Q: What is true regarding antigenic shift?

Due to genetic recombination. **Explanation:** The concept of antigenic variation in the Influenza virus is a high-yield topic for NEET-PG, categorized into two types: **Antigenic Shift** and **Antigenic Drift**. **Why the correct answer is right:** **Antigenic Shift** refers to an abrupt, major change in the virus resulting in new Hemagglutinin (H) and/or Neuraminidase (N) proteins. This occurs due to **genetic recombination** (specifically **reassortment**) of genetic segments between two or more different influenza strains infecting the same cell. Because the population has little to no immunity against this new subtype, it often leads to **Pandemics**. **Analysis of Incorrect Options:** * **A. Gradual changes:** This describes Antigenic Drift, which involves slow, continuous changes over time. * **B. Seen in influenza A and B:** Antigenic Shift occurs **only in Influenza A** because it has a broad host range (humans, birds, pigs), allowing for reassortment. Influenza B only undergoes Drift. * **D. Due to point mutation:** This is the mechanism for **Antigenic Drift**. Point mutations in the RNA lead to minor changes in the surface antigens, necessitating the update of annual flu vaccines. **High-Yield Clinical Pearls for NEET-PG:** * **Shift = Pandemic:** Sudden, major change, Influenza A only, reassortment. * **Drift = Epidemic:** Gradual, minor change, Influenza A and B, point mutation. * **Host for Shift:** The pig is often called the "mixing vessel" for antigenic shift between avian and human influenza viruses. * **Vaccine Strain:** The WHO reviews the vaccine composition annually primarily due to Antigenic Drift.

Q: Which virus is associated with Hodgkin's lymphoma?

EBV (Epstein-Barr virus). **Explanation:** The correct answer is **EBV (Epstein-Barr virus)**. Epstein-Barr virus (Human Gammaherpesvirus 4) is a potent oncogenic virus with a strong tropism for B-lymphocytes. In the pathogenesis of **Hodgkin’s Lymphoma (HL)**, EBV is found in approximately 40-50% of cases (particularly the Mixed Cellularity subtype). The virus expresses the **LMP-1 (Latent Membrane Protein-1)** oncogene, which mimics CD40 signaling, activating the NF-κB and JAK/STAT pathways. This promotes the survival and proliferation of the characteristic **Reed-Sternberg cells**. **Analysis of Incorrect Options:** * **CMV (Cytomegalovirus):** While a member of the Herpesviridae family, it is primarily associated with congenital infections and infectious mononucleosis-like syndromes in immunocompromised patients, not lymphomas. * **HHV-6:** This virus causes Roseola Infantum (Exanthema Subitum). Although it can remain latent in T-cells, it has no established causative link to Hodgkin’s Lymphoma. * **HHV-8:** Also known as KSHV, this virus is specifically associated with **Kaposi Sarcoma**, Primary Effusion Lymphoma (PEL), and Multicentric Castleman Disease, but not classic Hodgkin’s Lymphoma. **High-Yield Clinical Pearls for NEET-PG:** * **EBV Associations:** Burkitt Lymphoma (t(8;14)), Nasopharyngeal Carcinoma, Oral Hairy Leukoplakia (in HIV), and Post-transplant Lymphoproliferative Disorder (PTLD). * **HL Subtypes:** EBV is most commonly associated with the **Mixed Cellularity** subtype and least commonly with the Lymphocyte Predominant subtype. * **Reed-Sternberg Cells:** Look for "Owl’s eye" appearance; these cells are typically **CD15+ and CD30+** (except in the Nodular Lymphocyte Predominant variant).

Q: Epstein-Barr virus has been implicated in the following malignancies except?

Multiple myeloma. **Explanation:** Epstein-Barr Virus (EBV), also known as Human Herpesvirus 4 (HHV-4), is a potent oncogenic virus that primarily infects B-lymphocytes and epithelial cells. It is strongly associated with several lymphoid and epithelial malignancies due to its ability to induce immortalization of B-cells. **Why Multiple Myeloma is the correct answer:** Multiple Myeloma is a plasma cell dyscrasia characterized by the malignant proliferation of plasma cells. Unlike other B-cell malignancies, there is **no established causal link** between EBV infection and the development of Multiple Myeloma. Its pathogenesis is primarily linked to genetic mutations (e.g., MYC, RAS) and bone marrow microenvironment changes rather than viral oncogenesis. **Analysis of Incorrect Options:** * **Hodgkin’s Disease:** EBV is found in approximately 40-50% of cases, particularly the **Mixed Cellularity** subtype. The virus is often detected within the characteristic Reed-Sternberg cells. * **Non-Hodgkin’s Lymphoma (NHL):** EBV is a major driver in several NHLs, most notably **Burkitt Lymphoma** (endemic form), Immunoblastic lymphoma, and Primary CNS Lymphoma (especially in HIV/AIDS patients). * **Nasopharyngeal Carcinoma:** There is a 100% association with the **undifferentiated (Type III)** variant of nasopharyngeal carcinoma, common in Southern China and parts of Africa. **High-Yield Clinical Pearls for NEET-PG:** * **Receptor:** EBV enters B-cells via the **CD21** receptor (also the receptor for C3d complement). * **Diagnosis:** Atypical lymphocytes (Downey cells) on peripheral smear; Monospot test (detects heterophile antibodies). * **Other EBV-associated conditions:** Infectious Mononucleosis (Glandular fever), Oral Hairy Leukoplakia (in HIV), and Gastric Carcinoma (subset of cases). * **Burkitt Lymphoma Translocation:** t(8;14) involving the *c-myc* gene.

Question 1

A child with agammaglobulinemia presents with respiratory tract infection and diarrhea. What is the most likely infectious agent?

Accepted Answer

Rotavirus

Answer

Cocksackie virus

Answer

Shigella

Answer

None of the above

Question 2

A virus produces neonatal infections and infections in immunocompromised patients such as AIDS patients. The most common clinical presentation involves floaters, visual field deficits, and painless loss of vision. It can also produce encephalitis and may cause calcifying lesions in the CNS. What is this virus most likely?

Accepted Answer

Cytomegalovirus (CMV)

Answer

Epstein-Barr Virus (EBV)

Answer

Herpes Simplex Virus (HSV)

Answer

Human Immunodeficiency Virus (HIV)

Question 3

A 65-year-old patient with chronic obstructive airway disease presented with headache, rhinorrhoea, myalgia, and retro-orbital and throat pain. He was managed conservatively. After 3-4 days, he presented again with cough, fever, and severe dyspnoea, requiring oxygen therapy. His condition deteriorated further, and ABG analysis showed pH 7.42, pCO2 41 mm Hg, pO2 34 mm Hg, and HCO3- 26 mmol/L. Blood cultures and sputum samples were negative for bacterial infections. Which of the following statements about the causative organism of this condition is FALSE?

Accepted Answer

Haemolysins are present.

Answer

The organism is mostly spherical but filamentous in fresh isolates.

Answer

The organism is segmented with 8 pieces of RNA.

Answer

The diameter of the nucleocapsid is 9nm.

Question 4

Which of the following is associated with nasopharyngeal cancer?

Accepted Answer

Human Herpesvirus 4 (HHV-4)

Answer

Human Herpesvirus 1 (HHV-1)

Answer

Human Herpesvirus 2 (HHV-2)

Answer

Human Herpesvirus 3 (HHV-3)

Question 5

Fatal familial insomnia is associated with which type of disease?

Accepted Answer

Prion disease

Answer

Degeneration disease

Answer

Neoplastic disease

Answer

Vascular disease

Question 6

All are true about hepatitis viruses EXCEPT?

Accepted Answer

Hepatitis A virus (HAV) leads to most cases of fulminant hepatitis.

Answer

Hepatitis C virus (HCV) leads to chronic liver disease.

Answer

Hepatitis A virus (HAV) is transmitted via the fecal-oral route.

Answer

Hepatitis B virus (HBV) can cause hepatocellular carcinoma.

Question 7

Elevated IgG and IgM antibody titers to parvovirus suggest a diagnosis of which one of the following?

Accepted Answer

Fifth disease

Answer

Acute Lyme disease

Answer

Possible hepatitis B infection

Answer

Possible subacute sclerosing panencephalitis

Question 8

What is true regarding antigenic shift?

Accepted Answer

Due to genetic recombination

Answer

Gradual changes

Answer

Seen in influenza A and B

Answer

Due to point mutation

Question 9

Which virus is associated with Hodgkin's lymphoma?

Accepted Answer

EBV (Epstein-Barr virus)

Answer

CMV (Cytomegalovirus)

Answer

HHV6 (Human herpesvirus 6)

Answer

HHV8 (Human herpesvirus 8)

Question 10

Epstein-Barr virus has been implicated in the following malignancies except?

Accepted Answer

Multiple myeloma

Answer

Hodgkin's disease

Answer

Non-Hodgkin's lymphoma

Answer

Nasopharyngeal carcinoma

Virology — MCQs

Virology — MCQs

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