Virology (Hepatitis, Herpes, HIV, Arboviruses, Respiratory Viruses) MCQs

Microbiology · 107 free questions with answers & explanations.

1. A 28-year-old woman's hepatitis B serology: HBsAg positive, anti-HBc IgM positive, HBeAg positive, anti-HBs negative. This serological pattern indicates:
2. An AIDS patient with CD4 count of 50 cells/μL develops a painful dermatomal vesicular rash across the thorax. The virus responsible establishes latency in which anatomical site?
3. A neutropenic post-transplant patient develops CMV pneumonitis. The drug of choice for CMV disease is ganciclovir. Which enzyme of CMV phosphorylates ganciclovir to its active monophosphate form?
4. A traveler returning from South-East Asia presents with high fever, severe myalgia, retro-orbital pain, and a maculopapular rash with islands of sparing. Platelet count is 60,000/μL and tourniquet test is positive. Dengue serology is positive. The vector is:
5. HIV replication cycle: after the viral RNA is reverse-transcribed into double-stranded DNA, which step allows the viral DNA to be stably maintained in the host cell genome?
6. A patient with chronic HBV infection has the following serology: HBsAg (+), HBeAg (-), Anti-HBe (+), HBV DNA 5×10^5 IU/mL, elevated ALT. This pattern represents which clinical entity?
7. HIV-1 reverse transcriptase lacks 3'→5' exonuclease proofreading activity, resulting in a high mutation rate. Among the non-nucleoside reverse transcriptase inhibitors (NNRTIs), resistance develops rapidly with monotherapy because a single mutation at which critical binding site residue confers class resistance?
8. Varicella-zoster virus (VZV) establishes latency in sensory ganglia and reactivates as herpes zoster. The key viral protein that maintains latency by suppressing lytic gene expression in dorsal root ganglion neurons is:
9. During a dengue outbreak, serotype-2 (DENV-2) is identified. A patient who had dengue serotype-1 (DENV-1) three years ago now presents with dengue hemorrhagic fever (DHF). The immunopathological basis of increased severity on secondary infection is:
10. HIV-1 integrase inhibitors (e.g., raltegravir) block which specific step of the HIV replication cycle?
11. HBsAg can be detected in blood even when serum HBV DNA is very low. The reason is that HBsAg is:
12. A child with encephalitis has CSF showing lymphocytic pleocytosis and hemorrhagic necrosis of temporal lobes on MRI. HSV-1 encephalitis is suspected. The molecular mechanism of HSV-1 latency reactivation involves:
13. Dengue hemorrhagic fever (DHF) is more severe during secondary infection with a different dengue serotype. The immunopathological mechanism is:
14. Hepatitis D virus (HDV) requires HBV coinfection because HDV:
15. A 32-year-old man is found to be HBsAg positive, HBeAg negative, with HBV DNA of 12,000 IU/mL and elevated ALT on two occasions 6 months apart. Anti-HBe is positive. He has no cirrhosis on liver biopsy. This serological pattern is consistent with which phase of chronic HBV infection, and what treatment is recommended?
16. HIV integrase strand transfer inhibitors (INSTIs) — raltegravir, elvitegravir, dolutegravir, bictegravir — prevent viral DNA integration into the host genome. Which step specifically does this drug class inhibit?
17. A 25-year-old presents with vesicular rash over the T6 dermatome, severe burning pain, and a history of chickenpox at age 7. The causative virus persists in which structure after primary infection?
18. Hepatitis E virus (HEV) infection during pregnancy is associated with particularly high mortality. Which immunological mechanism is most important in HEV-associated fulminant hepatic failure in pregnancy?
19. Dengue virus NS1 antigen-capture ELISA is useful in which phase of dengue fever for laboratory diagnosis?
20. A 35-year-old HBsAg-positive patient shows HBeAg negativity, high HBV DNA (>2000 IU/mL) and elevated ALT. Anti-HBe is positive. What mutation is responsible for this pattern and what is its clinical significance?
21. HIV-1 uses multiple co-receptors for entry into cells. What is the significance of the CCR5Δ32 homozygous mutation in individuals exposed to HIV-1 R5 strains?
22. Varicella-zoster virus (VZV) establishes latency in dorsal root ganglia after primary chickenpox. During reactivation (herpes zoster), what is the mechanism of pain (post-herpetic neuralgia) that persists after skin lesion resolution?
23. Dengue virus causes two consecutive infections with different serotypes to produce dengue hemorrhagic fever (DHF)/dengue shock syndrome (DSS). Which immunological mechanism is responsible for the increased disease severity in secondary dengue infection?
24. Hepatitis C virus (HCV) evades innate immune detection primarily by which mechanism at the level of interferon signaling?
25. In chronic hepatitis B, the serum marker pattern shows: HBsAg positive, HBeAg negative, anti-HBe positive, with markedly elevated HBV DNA on PCR. Liver biopsy shows active hepatitis. This pattern is most consistent with:
26. HIV integrase strand transfer inhibitors (INSTIs) like raltegravir and dolutegravir block a specific step in the HIV replication cycle. The HIV integrase enzyme catalyses which two sequential reactions?
27. Dengue fever serology: A patient presents on day 4 of fever with dengue suspicion. NS1 antigen ELISA is positive. Regarding dengue diagnostics, NS1 antigen is detectable in serum during which period?
28. Herpes simplex virus (HSV) establishes latency in sensory ganglia. During reactivation, the latency-associated transcript (LAT) plays which role in neuronal survival?
29. Influenza virus antigen shift (antigenic shift) occurs by which mechanism and leads to what epidemiological consequence?
30. A 28-year-old man tests: HBsAg negative, anti-HBs positive, anti-HBc IgG positive, anti-HBe positive, HBV DNA undetectable. What is the correct interpretation of this serological profile?
31. HIV-1 enters CD4+ T cells through its gp120-gp41 envelope complex. After gp120 binds CD4 and a co-receptor, gp41 mediates fusion. Which co-receptor is preferentially used by macrophage-tropic (R5) strains of HIV-1, and why is this important for transmission?
32. A 7-year-old child presents with prodromal fever, coryza, Koplik's spots on the buccal mucosa, and then a maculopapular rash descending from the face. Which immune effector mechanism is responsible for the rash?
33. Dengue fever is caused by DENV 1–4 serotypes transmitted by Aedes mosquitoes. Secondary infection with a different serotype leads to severe dengue (dengue haemorrhagic fever/DSS). The primary immunopathological mechanism of plasma leakage in severe dengue is:
34. A 60-year-old immunosuppressed renal transplant recipient presents with fever, pneumonitis, and low CD4 count. Bronchoscopy shows cytomegalic cells with owl-eye intranuclear inclusions. What specific cellular mechanism does CMV exploit to downregulate MHC I and evade CD8+ T-cell recognition?
35. A 28-year-old woman in her third trimester of pregnancy tests positive for HBsAg. Further testing shows HBeAg positive, anti-HBe negative and serum HBV DNA of 8 × 10⁷ IU/mL. What is the risk of vertical transmission to the neonate without prophylaxis, and what prophylaxis strategy reduces this risk?
36. HIV-1 uses which co-receptor predominantly for infection of macrophages early in HIV disease, and which co-receptor is predominantly used by T-tropic strains in advanced AIDS?
37. A 25-year-old man presents with vesicular eruption on the tip of the nose (Hutchinson's sign) and painful eye. Slit-lamp examination shows pseudodendrites on the cornea. Which herpes virus is responsible, and what is the significance of Hutchinson's sign?
38. A 20-year-old student from Delhi develops fever, severe headache, retro-orbital pain, myalgia and a maculopapular rash on day 4. NS1 antigen is positive on day 3. Platelet count falls to 60,000/µL. Which test would confirm dengue on day 8 of illness when NS1 is no longer detectable?
39. Influenza virus undergoes 'antigenic shift.' Which molecular event specifically constitutes antigenic shift, and why does it cause pandemic influenza rather than seasonal epidemics?
40. A neonate born to an anti-HCV positive mother is tested for HCV infection at 18 months of age using anti-HCV ELISA — the test is positive. What is the correct interpretation and the recommended next step?
41. A 30-year-old pregnant woman in her first trimester tests anti-HCV positive on screening. The next appropriate step to confirm active infection is:
42. Which HIV serological marker indicates the narrowest 'window period' for detecting acute HIV infection, even before antibodies develop?
43. A neonate develops disseminated herpes with hepatitis and encephalitis at day 5 of life. His mother had no visible genital lesions. The preferred treatment is:
44. Dengue fever diagnosis: On day 1 of fever the most sensitive test is NS1 antigen detection. On day 7, the test with highest sensitivity is:
45. In the post-exposure prophylaxis protocol for rabies following a category III exposure (deep laceration from a dog of unknown vaccination status), the ESSEN intramuscular regimen consists of:
46. A 30-year-old man presents with jaundice, right hypochondriac pain, and dark urine. Serology shows: HBsAg positive, Anti-HBc IgM positive, HBeAg positive, Anti-HBs negative, Anti-HBe negative, HBV DNA 2 × 10⁸ IU/mL, Anti-HCV negative. This pattern MOST likely represents:
47. An HIV-positive patient on ART has an undetectable viral load but a CD4 count of 85 cells/μL after 3 years of therapy. He develops oral thrush and is started on fluconazole. His current regimen includes tenofovir, emtricitabine, and efavirenz. The immunological non-response (poor CD4 recovery despite viral suppression) is termed:
48. During a dengue outbreak, a 22-year-old man presents on day 5 of illness with fever, thrombocytopenia (platelets 28,000/μL), and positive tourniquet test. NS1 antigen test is negative. Anti-dengue IgM and IgG are BOTH positive with high IgG titers. This serological pattern suggests:
49. Herpes simplex encephalitis (HSE) in adults most commonly results from reactivation of latent HSV-1 from the trigeminal ganglion with spread to the temporal lobe. The BEST initial diagnostic test for HSE when CSF is obtained is:
50. SARS-CoV-2 uses which host cell receptor for primary attachment, and which viral protein mediates this interaction after priming by a host serine protease?
51. A 30-year-old with chronic hepatitis B (HBeAg-negative, HBsAg-positive, anti-HBe-positive) has HBV DNA of 8000 IU/mL and ALT 3× upper limit. A mutation in the pre-core region (G1896A) is detected. This mutation causes:
52. A 22-year-old immunocompromised patient develops progressive painful perianal ulcers. Tzanck smear shows multinucleated giant cells. PCR on the ulcer swab is positive for HSV-2. The drug of choice and its mechanism are:
53. Dengue NS1 antigen ELISA is positive on day 2 of fever. On day 7, the patient is referred for thrombocytopenia (platelets 25,000/μL) and hematocrit rise. Which serological finding confirms dengue secondary infection at this stage?
54. A 55-year-old poultry worker develops severe pneumonia with lymphopenia and very high ferritin. Rapid influenza test is negative. Nasopharyngeal swab RT-PCR detects H5 haemagglutinin. Which statement about this virus is most accurate?
55. A pregnant woman at 10 weeks gestation is confirmed to have acute CMV primary infection by serology (IgM positive, IgG positive, low IgG avidity index). She is counselled that the risk of vertical transmission and fetal damage is highest at:
56. A 32-year-old healthcare worker has the following hepatitis B serology: HBsAg negative, anti-HBs positive (150 IU/L), anti-HBc IgG positive, anti-HBc IgM negative, HBeAg negative, anti-HBe positive. What does this serological profile most likely represent?
57. A 25-year-old immunocompetent patient has recurrent genital herpes confirmed by PCR as HSV-2. He enquires about suppressive antiviral therapy. Which of the following is the correct rationale for valacyclovir suppressive therapy over episodic therapy in this patient?
58. A clinician wants to distinguish dengue fever from dengue haemorrhagic fever serologically during the acute phase (day 3 of illness). Serum NS1 antigen is positive. Which additional test best differentiates primary from secondary dengue infection at this stage?
59. An HIV-positive patient on ART with undetectable viral load develops oral hairy leukoplakia (OHL) on the lateral tongue. Biopsy shows koilocytes. PCR confirms EBV in lesional tissue. This condition is associated with which EBV product specifically driving epithelial cell proliferation in OHL?
60. A 30-year-old pregnant woman at 10 weeks gestation is found to be HBsAg positive. Her HBeAg is positive, anti-HBe is negative, and HBV DNA is 2 × 10^8 IU/mL. What is the most appropriate intervention to prevent mother-to-child transmission (MTCT)?
61. A 25-year-old man presents with painful grouped vesicles on an erythematous base on the penis. Tzanck smear shows multinucleated giant cells with intranuclear inclusions. PCR on vesicle fluid is positive for HSV-2. He reports 4 recurrences in the past year. What is the most appropriate management?
62. A 32-year-old man newly diagnosed with HIV has CD4 count 320 cells/µL and HIV-1 RNA 85,000 copies/mL. The preferred first-line ART regimen in India (NACO 2022 guidelines) for a treatment-naive patient without specific comorbidities is:
63. A patient presents with dengue fever. On day 4 of illness, NS1 antigen ELISA is negative, but IgM anti-dengue antibody is positive with IgG negative. This serological profile is most consistent with:
64. Reverse transcriptase-PCR detects SARS-CoV-2 RNA in a nasopharyngeal swab. The E gene Ct value is 18. A second confirmatory PCR targeting the N gene shows Ct 19. What does this low Ct value indicate clinically?
65. A 35-year-old with chronic hepatitis B (HBeAg positive, HBV DNA 8 log IU/mL, ALT 3× ULN) needs antiviral therapy. He is planning fatherhood. The preferred first-line antiviral with the highest barrier to resistance is:
66. A 28-year-old male presenting with fever, lymphadenopathy, pharyngitis, and a transient maculopapular rash tests HIV-1/2 antibody negative but HIV-1 p24 antigen positive by 4th generation combination assay. The most appropriate next step is:
67. Dengue fever is distinguished from dengue hemorrhagic fever (DHF) primarily by the presence of:
68. A renal transplant patient on tacrolimus develops encephalitis. MRI shows T2 hyperintensities in the temporal lobe. CSF PCR for HSV-1 DNA is positive. The appropriate treatment regimen is:
69. A patient with advanced HIV (CD4 count 40 cells/µL) presents with progressive multifocal leukoencephalopathy (PML). The causative virus and its cell tropism are:
70. A 28-year-old pregnant woman has a positive HBsAg test. Further serology shows HBeAg positive, anti-HBe negative, HBV DNA > 2 × 10^6 IU/mL, and ALT is 22 U/L (normal). Her HBsAg has been positive for 3 years. This serological pattern is best classified as:
71. A neonate born to an HSV-2 seropositive mother develops vesicular skin rash, lethargy, and seizures at day 7 of life. CSF PCR for HSV is positive. The drug of choice and recommended duration of treatment is:
72. A patient on antiretroviral therapy has a viral load of 25,000 copies/mL after 6 months despite reported adherence. Genotypic resistance testing shows a M184V mutation in the reverse transcriptase gene. Which drug has this mutation primarily arisen against?
73. Dengue NS1 antigen is detectable in serum during the febrile phase (days 1–5). Which statement best describes the kinetics of dengue antibody responses in secondary dengue compared to primary dengue?
74. A 60-year-old immunocompromised patient post-renal transplant develops fever and mononucleosis-like syndrome at week 8. CMV pp65 antigenemia assay shows 20 positive cells/200,000 WBCs. Which treatment is appropriate?
75. A patient is diagnosed with chronic hepatitis B. HBsAg is positive for >6 months, HBeAg is positive, HBV DNA is 2×10^7 IU/mL, and ALT is 3× ULN. Which serological marker indicates active viral replication and correlates with infectivity?
76. A 25-year-old with HIV (not on ART, CD4 150 cells/µL) presents with vesicular lesions in a dermatomal distribution over the T8 dermatome plus three adjacent dermatomes. New vesicles continue to appear. What is the diagnosis and what antiviral is indicated?
77. Which HIV viral enzyme is targeted by integrase strand transfer inhibitors (INSTIs), and what is the mechanism of action of raltegravir?
78. During a dengue outbreak, a patient in day 4 of illness has fever, thrombocytopenia (platelets 40,000/µL), and a tourniquet test positive. Which combination of diagnostic tests is most appropriate at this stage?
79. A 6-month-old infant develops acute bronchiolitis with wheezing and respiratory distress. Nasopharyngeal aspirate rapid antigen test is positive for respiratory syncytial virus (RSV). Which protein of RSV is the target for passive prophylaxis with palivizumab?
80. A pregnant woman's antenatal serology shows: HBsAg positive, HBeAg positive, anti-HBc IgM negative, anti-HBc IgG positive, HBV DNA 5 × 10^7 IU/mL. She is at week 28 of gestation. Which management strategy best reduces the risk of perinatal hepatitis B transmission?
81. A patient with HIV (CD4 count 90/µL) develops painful vesicles in the V1 dermatomal distribution of the trigeminal nerve, with ipsilateral conjunctival injection and decreased corneal sensation. VZV PCR of vesicle swab is positive. Which antiviral regimen and dose is recommended for this sight-threatening herpes zoster ophthalmicus?
82. An HIV patient has a plasma viral load of 180,000 copies/mL and CD4 count of 250/µL at baseline. After 6 months on TDF + 3TC + EFV, viral load remains at 95,000 copies/mL. Resistance testing reveals M184V mutation. What is the significance of M184V in clinical management?
83. During a dengue outbreak, a patient on day 6 of illness has defervescence but develops severe abdominal pain, pleural effusion on chest X-ray and platelet count 18,000/µL. NS1 antigen test is now negative. Which serological test would be most useful at this stage?
84. Hepatitis C genotype 3 is the predominant genotype in India. A treatment-naive patient with HCV genotype 3 and compensated cirrhosis is being evaluated. Which DAA regimen is recommended by current Indian guidelines?
85. A pregnant woman at 12 weeks gestation is found to have HBsAg positive, HBeAg positive, and HBV DNA of 2 × 10^8 IU/mL. To prevent mother-to-child transmission (MTCT), the recommended antiviral strategy in addition to neonatal HBIg and hepatitis B vaccine at birth is:
86. The NS1 antigen of dengue virus is detected in serum during which time window post-illness onset, and its detection serves which diagnostic purpose?
87. Herpes simplex encephalitis (HSE) is caused by HSV-1 in adults and characteristically involves which brain region, and what is the test of choice for rapid laboratory diagnosis?
88. In HIV-infected patients with advanced immunosuppression (CD4 <50 cells/µL), prophylaxis against Cytomegalovirus (CMV) retinitis is indicated. The drug used for CMV prophylaxis or pre-emptive therapy is:
89. A 35-year-old woman with HIV (CD4 count 50 cells/µL) has progressive painless vision loss in the right eye. Fundoscopy shows 'pizza-pie' retinal haemorrhages and perivascular yellow-white exudates. Aqueous humor PCR is positive for CMV. What is the treatment of choice for CMV retinitis in this setting?
90. Influenza A viruses are classified by their surface glycoproteins. The current seasonal influenza H3N2 subtype has which hemagglutinin (HA) and neuraminidase (NA) combination, and which host receptor does human-adapted influenza preferentially bind?
91. A 28-year-old from Rajasthan with recent Aedes aegypti-endemic area exposure develops fever, severe joint pain (arthralgia), and a maculopapular rash on day 3. RT-PCR is positive for Chikungunya virus. Which statement about Chikungunya is CORRECT?
92. A patient with HIV and CD4 count of 80 cells/µL presents with progressive multifocal leukoencephalopathy (PML). The causative virus and its cellular receptor are:
93. In hepatitis B infection, which serological marker indicates ongoing viral replication and high infectivity?
94. Regarding Nipah virus encephalitis, which of the following is CORRECT about its transmission and diagnosis?
95. A patient has confirmed genotype 1b chronic hepatitis C infection. Current first-line treatment per Indian guidelines is:
96. A 3-year-old child presents with high fever, drooling, difficulty swallowing, and vesicular lesions on the soft palate, tonsillar pillars, and posterior pharynx. There are also vesicles on the palms and soles. The responsible pathogen belongs to which viral family?
97. A 35-year-old pregnant woman at 12 weeks gestation is found to be rubella IgM-positive on routine screening. Her obstetrician is concerned about congenital rubella syndrome. Which of the following is NOT a feature of congenital rubella syndrome?
98. A virologist is studying a newly isolated enveloped RNA virus. She finds that the virus replicates entirely in the cytoplasm, has a negative-sense single-stranded RNA genome, and uses its own RNA-dependent RNA polymerase (RdRp) packaged within the virion for transcription. This description is most consistent with:
99. A 40-year-old man with chronic liver disease undergoes liver biopsy which shows 'ground-glass hepatocytes'. Immunostaining of these cells would most likely be positive for:
100. A 25-year-old immunocompetent patient presents with a painful unilateral vesicular rash in a dermatomal distribution over the right thorax accompanied by intense burning pain. This is caused by reactivation of a latent virus that establishes latency in:
101. A public health officer investigating an influenza outbreak notes that a new pandemic strain has emerged by combining gene segments from two different influenza A strains infecting the same host cell. This mechanism of generating new influenza strains with novel surface antigens is called:
102. Oseltamivir (Tamiflu) is effective against influenza A and B. Its mechanism of action is:
103. A patient co-infected with HIV and Hepatitis B virus (HBV) is being started on antiretroviral therapy (ART). Which antiretroviral agent should be included in the regimen because it is also active against HBV?
104. A renal transplant recipient on tacrolimus develops painful perianal ulcers. Swab PCR is positive for HSV-2, but the lesions fail to respond to 10 days of aciclovir 400 mg three times daily. The next appropriate step is:
105. A 10-year-old child bitten by a stray dog 2 months ago now develops hydrophobia, aerophobia, hypersalivation and progressive encephalitis. Post-mortem brain examination shows Negri bodies in Purkinje cells of cerebellum and pyramidal cells of hippocampus. What are Negri bodies composed of?
106. Parvovirus B19 infects erythroblasts in bone marrow. In a patient with hereditary spherocytosis (chronic haemolytic anaemia), acute Parvovirus B19 infection leads to a dramatically low haematocrit within days. What is this clinical syndrome called, and why are patients with haemolytic anaemia at especially high risk?
107. During an outbreak investigation of aseptic meningitis in children in a nursery school, faecal samples are collected. Which enterovirus is the most common cause of aseptic meningitis, and which cell culture medium best isolates it?