Virology — MCQs

Virology Indian Medical PG Practice Questions and MCQs

Question 181: Antenatal maternal HIV diagnosis is of importance in:

A. Preventing vertical transmission (Correct Answer)
B. Terminating pregnancy
C. Discharging the patient
D. Isolating the patient

Explanation: **Explanation:** The primary goal of diagnosing HIV in a pregnant woman is to initiate interventions that reduce the risk of **Mother-to-Child Transmission (MTCT)**, also known as vertical transmission. Without intervention, the risk of transmission is approximately 20–45%; however, with timely diagnosis and management, this can be reduced to **less than 1%**. **Why the correct answer is right:** Antenatal diagnosis allows for the implementation of the **Prevention of Mother-to-Child Transmission (PMTCT)** protocol. This includes: 1. **Antiretroviral Therapy (ART):** Initiating lifelong ART for the mother regardless of CD4 count to achieve viral suppression. 2. **Safe Delivery Practices:** Choosing the mode of delivery based on viral load. 3. **Post-exposure Prophylaxis (PEP):** Administering Nevirapine or Zidovudine to the newborn. 4. **Feeding Advice:** Counseling on exclusive breastfeeding or replacement feeding to minimize postnatal transmission. **Why other options are incorrect:** * **B. Terminating pregnancy:** HIV is not a medical indication for Medical Termination of Pregnancy (MTP). With modern ART, HIV-positive women can deliver healthy, HIV-negative infants. * **C. Discharging the patient:** Diagnosis necessitates closer follow-up and specialized obstetric care, not discharge. * **D. Isolating the patient:** HIV is transmitted through blood and body fluids, not casual contact. Standard precautions are sufficient; social or medical isolation is unnecessary and stigmatizing. **High-Yield Clinical Pearls for NEET-PG:** * **Most common timing of transmission:** During labor and delivery (Intrapartum). * **PPTCT Regimen (India):** All HIV-positive pregnant women should be started on the **TLE Regimen** (Tenofovir + Lamivudine + Efavirenz) immediately. * **Infant Prophylaxis:** Syrup **Nevirapine** is given to the infant for 6 weeks (extendable to 12 weeks if the mother received ART late). * **Diagnosis in Infants:** Use **HIV DNA PCR** (Virological test) at 6 weeks; antibody tests (ELISA) are unreliable until 18 months due to persisting maternal antibodies.

Question 182: Which of the following is NOT included in the diagnostic criteria for AIDS?

A. CD4 count < 200 cells/mm³
B. CD8 count < 500 cells/mm³
C. CD4:CD8 ratio = 1
D. Presence of any of the opportunistic infections like tuberculosis, Pneumocystis carinii pneumonia, or cytomegalovirus disease (Correct Answer)

Explanation: The diagnosis of AIDS (Acquired Immunodeficiency Syndrome) is based on specific immunological and clinical criteria defined by the WHO and CDC. **Explanation of the Correct Answer:** Option **D** is technically the "incorrect" statement in the context of this question because it is **included** in the diagnostic criteria. According to the CDC classification, a patient is diagnosed with AIDS if they are HIV-positive and present with any **AIDS-defining illness** (Stage 3 HIV). These include opportunistic infections like *Pneumocystis jirovecii* pneumonia (PCP), extrapulmonary tuberculosis, esophageal candidiasis, and CMV retinitis, or certain malignancies like Kaposi sarcoma. **Analysis of Other Options:** * **Option A (CD4 count < 200 cells/mm³):** This is a primary immunological criterion for AIDS. Even in the absence of symptoms, a CD4 count below this threshold confirms the diagnosis. * **Option B (CD8 count < 500 cells/mm³):** This is **not** a diagnostic criterion for AIDS. While CD8 counts may fluctuate during HIV infection, they are not used to define the transition from HIV to AIDS. * **Option C (CD4:CD8 ratio = 1):** In a healthy individual, the ratio is typically >1.5. In AIDS, the ratio **inverts** (becomes <1). A ratio of 1 is abnormal but is not a specific diagnostic cutoff for AIDS. *(Note: The question as phrased is a "negative" question. Options B and C are technically NOT criteria, while A and D ARE criteria. In NEET-PG, ensure you identify if the question asks for the "except" or "incorrect" statement.)* **High-Yield Clinical Pearls for NEET-PG:** * **Normal CD4 Count:** 500–1500 cells/mm³. * **Window Period:** The time between infection and the appearance of detectable antibodies (usually 2–8 weeks). The best test during this period is **p24 antigen** or **HIV RNA PCR**. * **Screening vs. Confirmatory:** ELISA is the screening test (high sensitivity); Western Blot was the traditional confirmatory test, though current protocols favor the **HIV-1/2 antigen-antibody immunoassay**. * **Most common opportunistic infection in India:** Tuberculosis. * **Most common opportunistic infection globally:** *Pneumocystis jirovecii*.

Question 183: Which of the following is NOT a complication of chickenpox?

A. Pancreatitis (Correct Answer)
B. Pneumonia
C. Encephalitis
D. Thrombocytopenia

Explanation: **Explanation:** Chickenpox, caused by the **Varicella-Zoster Virus (VZV)**, is typically a self-limiting childhood illness but can lead to several systemic complications, especially in adults and immunocompromised individuals. **Why Pancreatitis is the Correct Answer:** Pancreatitis is **not** a recognized or classic complication of primary Varicella infection. While VZV can affect multiple organ systems, the pancreas is rarely, if ever, a target during the acute phase of chickenpox. In contrast, pancreatitis is a well-known complication of other viral infections like **Mumps** and **Coxsackievirus B**. **Analysis of Incorrect Options:** * **Pneumonia:** This is the **most serious complication** of chickenpox in adults. It typically presents 3–5 days into the illness with cough and dyspnea. * **Encephalitis:** Neurological complications are well-documented. In children, **Acute Cerebellar Ataxia** (presenting with nystagmus and ataxia) is more common, while diffuse **Encephalitis** is more frequent in adults. * **Thrombocytopenia:** Hematological issues, including transient thrombocytopenia and purpura fulminans, can occur due to viral interference with platelet production or immune-mediated destruction. **High-Yield Clinical Pearls for NEET-PG:** * **Most common complication in children:** Secondary bacterial infection of skin lesions (usually *Staph. aureus* or *Strep. pyogenes*). * **Reye’s Syndrome:** A serious complication involving encephalopathy and liver failure, linked to **Aspirin** use during chickenpox. * **Congenital Varicella Syndrome:** Occurs if the mother is infected in the first 20 weeks of pregnancy; characterized by cicatricial skin scarring, limb hypoplasia, and chorioretinitis. * **Tzanck Smear:** Shows **Multinucleated Giant Cells** with Cowdry Type A intranuclear inclusion bodies.

Question 184: Coxsackie virus can be isolated by inoculating into which of the following?

A. Rabbit
B. Guinea pig
C. Suckling mice (Correct Answer)
D. Foot pad of mice

Explanation: **Explanation:** The **Coxsackie virus**, a member of the *Picornaviridae* family (Genus: *Enterovirus*), is uniquely characterized by its pathogenicity in **suckling mice** (mice less than 48 hours old). This is the gold standard classical method for isolation and differentiation of the virus into two groups: * **Group A:** Causes widespread **flaccid paralysis** due to generalized myositis of skeletal muscles. * **Group B:** Causes **spastic paralysis** due to focal myositis and necrotizing steatitis (inflammation of brown fat), often involving the pancreas and CNS. **Analysis of Incorrect Options:** * **A & B (Rabbit and Guinea Pig):** These animals are commonly used for producing antisera or for specific tests like the Paul-Bunnell test (Sheep RBCs) or Koch’s phenomenon (Tubercle bacilli), but they are not the primary isolation media for Coxsackie viruses. * **D (Foot pad of mice):** This is the specific site used for the cultivation of ***Mycobacterium leprae*** (the Shepard’s model), as the bacteria prefer the cooler temperature of the extremities. **High-Yield Clinical Pearls for NEET-PG:** * **Hand-Foot-Mouth Disease (HFMD):** Most commonly caused by Coxsackie **A16** and Enterovirus 71. * **Herpangina:** Characterized by vesicular lesions on the soft palate/fauces, caused by Group A. * **Bornholm Disease (Pleurodynia):** Also known as "Devil’s Grip," caused by Group B. * **Myocarditis & Dilated Cardiomyopathy:** Most frequently associated with **Coxsackie B** infections. * **Aseptic Meningitis:** Can be caused by both groups, but Group B is a more common culprit.

Question 185: What is the causative agent of Infectious mononucleosis?

A. Human Immunodeficiency Virus (HIV)
B. Hepatitis B Virus (HBV)
C. Herpes Simplex Virus (HSV)
D. Epstein-Barr virus (EBV) (Correct Answer)

Explanation: **Explanation:** **1. Why Epstein-Barr Virus (EBV) is correct:** Infectious Mononucleosis (IM), also known as "Glandular Fever" or the "Kissing Disease," is primarily caused by the **Epstein-Barr Virus (EBV)**, a member of the *Gammaherpesvirinae* subfamily (HHV-4). The virus infects B-lymphocytes by binding to the **CD21 receptor** (CR2). The characteristic clinical triad includes fever, pharyngitis, and lymphadenopathy. A hallmark of the disease is the presence of **atypical lymphocytes (Downey cells)** in the peripheral blood smear, which are actually activated T-cells responding to the infected B-cells. **2. Why the other options are incorrect:** * **HIV (Option A):** While Acute Retroviral Syndrome can mimic IM symptoms (fever, sore throat), HIV is a retrovirus that primarily targets CD4+ T-cells and leads to progressive immunodeficiency. * **HBV (Option B):** Hepatitis B is a hepadnavirus that primarily targets hepatocytes, leading to jaundice and liver inflammation, rather than a lymphoproliferative syndrome. * **HSV (Option C):** Herpes Simplex Virus typically causes vesicular lesions (cold sores or genital herpes) and encephalitis, not the systemic lymphadenopathy seen in IM. **3. NEET-PG High-Yield Pearls:** * **Diagnosis:** The **Paul-Bunnell Test** (detecting heterophile antibodies) is the classic screening test. * **Complication:** Patients treated with **Ampicillin or Amoxicillin** for a misdiagnosed sore throat often develop a characteristic maculopapular rash. * **Malignancy Link:** EBV is strongly associated with Burkitt Lymphoma (t(8;14)), Nasopharyngeal Carcinoma, and Hodgkin Lymphoma. * **Splenic Rupture:** Patients are advised to avoid contact sports due to the risk of spontaneous or traumatic splenic rupture.

Question 186: Which virus is associated with the Edmonston strain?

A. Hepatitis-B
B. Measles (Correct Answer)
C. Mumps
D. Rubella

Explanation: **Explanation:** The **Edmonston strain** is the parent strain of the **Measles virus** (Rubeola) used in the development of live-attenuated vaccines. It was originally isolated in 1954 by John Enders and Thomas Peebles from the blood of a young patient named David Edmonston. 1. **Measles (Correct):** The original Edmonston strain was further attenuated through multiple passages in human and chick embryo cells to create the **Edmonston-B** strain. Most modern measles vaccines used worldwide (such as the **Schwartz** and **Moraten** strains) are further derivatives of this original Edmonston isolate. 2. **Incorrect Options:** * **Hepatitis-B:** The vaccine is a recombinant subunit vaccine containing HBsAg produced in yeast (*Saccharomyces cerevisiae*). * **Mumps:** The most common vaccine strain is the **Jeryl Lynn** strain (named after the daughter of Maurice Hilleman). * **Rubella:** The standard vaccine strain used globally is **RA 27/3** (where RA stands for Rubella Abortus), isolated from the kidney cells of an aborted fetus. **High-Yield Clinical Pearls for NEET-PG:** * **Measles Vaccine:** It is a live-attenuated vaccine, typically administered at 9 months (as per the National Immunization Schedule in India) and 15-18 months (as MMR). * **Vitamin A:** Supplementation is mandatory during measles management to reduce morbidity and mortality (prevents blindness and pneumonia). * **Koplik Spots:** Pathognomonic bluish-white spots on an erythematous base found on the buccal mucosa opposite the lower second molars. * **SSPE (Subacute Sclerosing Panencephalitis):** A rare, late neurological complication caused by a persistent mutant measles virus.

Question 187: Which of the following cell types is NOT a target for the initiation and maintenance of HIV infection?

A. CD4 T cell
B. Macrophage
C. Dendritic cell
D. Neutrophil (Correct Answer)

Explanation: ### Explanation The primary mechanism of HIV entry into host cells depends on the interaction between the viral envelope glycoprotein **gp120** and the host cell **CD4 receptor**, along with co-receptors (**CCR5** or **CXCR4**). **Why Neutrophils are the Correct Answer:** Neutrophils (Option D) do not express the CD4 receptor on their surface. Therefore, they cannot be directly infected by HIV. While HIV infection can lead to secondary "neutropenia" or functional defects in neutrophils due to a compromised cytokine environment, these cells are not targets for viral entry, replication, or maintenance. **Analysis of Incorrect Options:** * **CD4 T cells (Option A):** These are the primary targets for HIV. The virus binds to CD4 and the CXCR4 co-receptor (T-tropic strains), leading to progressive depletion of these cells, which is the hallmark of AIDS. * **Macrophages (Option B):** Macrophages express CD4 and the **CCR5** co-receptor (M-tropic strains). They are resistant to the cytopathic effects of the virus, allowing them to serve as long-term **reservoirs** for HIV and transport the virus to the brain. * **Dendritic Cells (Option C):** These cells (including follicular dendritic cells and Langerhans cells) play a crucial role in the **initiation** of infection. They capture HIV in mucosal surfaces using the **DC-SIGN** receptor and transport the virus to regional lymph nodes, effectively "presenting" it to CD4 T cells. **High-Yield Clinical Pearls for NEET-PG:** * **Primary Receptor:** CD4. * **Co-receptors:** CCR5 (early infection/macrophages) and CXCR4 (late infection/T cells). * **Homozygous mutation in CCR5 (Δ32):** Confers resistance to HIV infection. * **Viral Entry Protein:** gp120 (attachment); gp41 (fusion). * **Reservoirs:** Macrophages and Memory CD4 T cells are the major anatomical and cellular reservoirs that prevent total viral clearance.

Question 188: Herpes simplex virus causes all except?

A. Encephalitis
B. Pharyngitis
C. Infectious mononucleosis (Correct Answer)
D. Whitlow

Explanation: **Explanation:** The correct answer is **Infectious Mononucleosis**. While this condition is caused by a member of the Herpesviridae family, it is specifically caused by **Epstein-Barr Virus (EBV/HHV-4)** and occasionally Cytomegalovirus (CMV), but **not** by Herpes Simplex Virus (HSV-1 or HSV-2). **Why the other options are incorrect:** * **Encephalitis:** HSV-1 is the most common cause of sporadic fatal viral encephalitis worldwide, typically involving the temporal lobes. * **Pharyngitis:** Primary HSV-1 infection in adults frequently presents as acute pharyngotonsillitis, while in children, it often manifests as gingivostomatitis. * **Whitlow (Herpetic Whitlow):** This is a painful infection of the finger caused by HSV-1 (often in healthcare workers or children) or HSV-2 (via autoinoculation from genital lesions). **High-Yield Clinical Pearls for NEET-PG:** * **HSV Encephalitis:** Look for "Temporal lobe involvement" and "Hemorrhagic necrosis" on MRI. CSF analysis shows lymphocytic pleocytosis and increased RBCs. * **Diagnosis:** The gold standard for HSV diagnosis is **PCR**. However, for exams, remember the **Tzanck Smear**, which shows **Multinucleated Giant Cells** with Cowdry Type A intranuclear inclusions. * **Infectious Mononucleosis Triad:** Fever, Pharyngitis, and Lymphadenopathy. Key lab findings include **Atypical lymphocytes (Downey cells)** and a positive Heterophile antibody (Monospot) test. * **Treatment:** Acyclovir is the drug of choice for HSV infections, acting as a nucleoside analog that inhibits viral DNA polymerase.

Question 189: BK virus affects which organ transplantation?

A. Liver
B. Kidney (Correct Answer)
C. Lung
D. Marrow

Explanation: **Explanation:** The **BK virus** is a member of the *Polyomaviridae* family. It is a ubiquitous virus that most individuals acquire during childhood, after which it remains **latent in the renal tubular epithelium** and uroepithelium. **Why Kidney is correct:** In the setting of profound immunosuppression, particularly following **renal transplantation**, the virus reactivates. This leads to **BK Virus-Associated Nephropathy (BKVAN)**, characterized by tubulointerstitial inflammation and graft dysfunction. It is a major cause of allograft failure, affecting up to 10% of kidney transplant recipients. It also causes **hemorrhagic cystitis** in bone marrow transplant patients. **Why other options are incorrect:** * **Liver:** While viruses like CMV or Hepatitis B/C are concerns in liver transplants, BK virus does not typically target hepatic tissue. * **Lung:** Lung transplant complications are more commonly associated with CMV or fungal infections (Aspergillus). * **Marrow:** While BK virus causes hemorrhagic cystitis in bone marrow recipients, the primary organ "affected" by the pathology of the virus itself (nephropathy) is the kidney. In the context of "organ transplantation" (solid organ), the kidney is the classic association. **High-Yield Clinical Pearls for NEET-PG:** 1. **Diagnosis:** Look for **"Decoy cells"** (cells with large intranuclear inclusions) in urine cytology. 2. **Mnemonic:** **B**K virus affects the **B**e**K**ay (BK) → **B**idney (Kidney). 3. **JC Virus:** A related Polyomavirus that causes **Progressive Multifocal Leukoencephalopathy (PML)** in immunocompromised patients. 4. **Treatment:** Primarily involves the reduction of immunosuppressive therapy and occasionally Cidofovir.

Question 190: Which of the following groups of viruses is most likely involved in viral meningitis?

A. Adenovirus
B. Enterovirus (Correct Answer)
C. Human papilloma virus
D. Poxvirus

Explanation: **Explanation:** **Enteroviruses** (specifically Coxsackievirus A and B, and Echoviruses) are the most common cause of viral (aseptic) meningitis worldwide, accounting for more than **85–90% of all cases**. They belong to the *Picornaviridae* family. These viruses typically follow a fecal-oral route of transmission, replicate in the pharynx and GI tract, and then spread hematogenously to the central nervous system. Clinical presentation usually includes fever, headache, photophobia, and meningeal signs, often occurring in seasonal outbreaks (summer and autumn). **Why other options are incorrect:** * **Adenovirus:** While it can cause respiratory infections, conjunctivitis, and hemorrhagic cystitis, it is a rare cause of meningitis, usually seen only in immunocompromised individuals. * **Human Papilloma Virus (HPV):** This virus is strictly epitheliotropic, causing cutaneous warts and mucosal lesions (including cervical cancer). It does not have a neurotropic phase and does not cause meningitis. * **Poxvirus:** This group (including Variola and Molluscum contagiosum) primarily causes skin lesions. While complications can occur, they are not standard causes of viral meningitis. **High-Yield Clinical Pearls for NEET-PG:** * **CSF Findings in Viral Meningitis:** Normal glucose, normal to slightly elevated protein, and **lymphocytic pleocytosis** (though neutrophils may predominate in the first 24 hours). * **Mollaret Meningitis:** Recurrent lymphocytic meningitis often associated with **HSV-2**. * **Most common cause of Viral Encephalitis:** Sporadic cases are most commonly caused by **HSV-1** (targeting the temporal lobes). * **Enterovirus 71:** Notable for causing Hand-Foot-Mouth Disease (HFMD) and severe neurological complications like brainstem encephalitis.

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Virology — MCQs

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