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🦠 VIROLOGY — COMPREHENSIVE NURSING NOTES

Microbiology | Nursing Exam Preparation | AIIMS NORCET / Staff Nurse Exams

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📌 1. INTRODUCTION

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📌 2. DEFINITION

Virus = A very small infectious particle (20–300 nm) that contains ONLY one type of nucleic acid (either DNA or RNA), surrounded by a protein coat. It can only replicate (make copies of itself) inside a living host cell.

• Virion = The complete, fully formed virus particle (outside the cell)
• Capsid = The protein shell/coat that protects the genetic material
• Envelope = A fat (lipid) layer that surrounds some viruses
• Nucleocapsid = Capsid + Nucleic acid (genetic material) together
• nm (nanometer) = 1 nm = one millionth of a millimeter (extremely tiny!)

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📌 3. STRUCTURE / MORPHOLOGY OF VIRUS

Diagram of Virus Structure

Basic Parts of a Virus:

Simple Diagram (Easy to draw in exams):

         ┌─────────────────────────┐
         │  GLYCOPROTEIN SPIKES    │  ← Attachment to host cell
         │  ┌─────────────────┐    │
         │  │   ENVELOPE      │    │  ← Lipid bilayer (only in some)
         │  │  ┌───────────┐  │    │
         │  │  │  CAPSID   │  │    │  ← Protein coat (capsomeres)
         │  │  │ (Protein) │  │    │
         │  │  │  NUCLEIC  │  │    │
         │  │  │  ACID     │  │    │  ← DNA or RNA
         │  │  │ (Core)    │  │    │
         │  │  └───────────┘  │    │
         │  └─────────────────┘    │
         └─────────────────────────┘

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📌 4. CLASSIFICATION OF VIRUSES

A. Based on Nucleic Acid (Most Important)

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B. Based on Capsid Shape (Symmetry)

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C. Based on Envelope

Nursing Tip: Enveloped viruses (HIV, Flu, Corona) are KILLED by hand washing with soap. Non-enveloped viruses (Polio, Rota, Norovirus) are MORE resistant — need stronger disinfectants.

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D. Major Virus Families (Classification Table)

ss = single-stranded | ds = double-stranded | RT = Reverse transcriptase | + = positive sense | − = negative sense

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📌 5. REPLICATION OF VIRUSES (Step-by-Step Flowchart)

STEP 1: ATTACHMENT (Adsorption)
Virus spike/surface protein binds to specific receptor on host cell surface
             ↓
STEP 2: PENETRATION (Entry)
Entire virus OR just nucleic acid enters the host cell
(Enveloped viruses: membrane fusion | Non-enveloped: endocytosis)
             ↓
STEP 3: UNCOATING
Capsid is removed — nucleic acid is released into the cell
             ↓
STEP 4: BIOSYNTHESIS
Host cell machinery reads viral DNA/RNA
→ Viral mRNA made → Viral proteins synthesized
→ New viral nucleic acid copied (replicated)
             ↓
STEP 5: ASSEMBLY (Maturation)
New viral proteins + new nucleic acid come together
→ New virus particles (virions) are assembled
             ↓
STEP 6: RELEASE
New viruses exit the cell by:
• Budding (enveloped viruses — cell survives temporarily)
• Lysis — cell bursts and dies (non-enveloped viruses)
             ↓
NEW VIRIONS infect more cells → Disease spreads

Memory Trick — APUBAR: Attachment → Penetration → Uncoating → Biosynthesis → Assembly → Release

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📌 6. PATHOGENESIS OF VIRAL INFECTION (How Viruses Cause Disease)

Virus enters body
(Respiratory tract / GIT / Skin / Blood / Sexual contact)
        ↓
Primary replication at entry site
        ↓
Viremia [Virus in blood] — spreads to target organs
        ↓
Virus attacks specific cells (Cell Tropism = viruses prefer certain cells)
Example: HIV → T-lymphocytes | Poliovirus → Motor neurons | Hepatitis → Liver cells
        ↓
Cell damage by:
1. Direct lysis (cell destruction)
2. Immune-mediated damage (body attacks infected cells)
3. Transformation (virus changes cell → cancer)
        ↓
DISEASE MANIFESTATIONS:
• Fever, inflammation, organ dysfunction
• Immunosuppression (HIV)
• Malignancy (HPV → Cervical cancer)
• Latency — virus hides and reactivates later (Herpes, VZV)

Types of Viral Infection:

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📌 7. SIGNS AND SYMPTOMS OF VIRAL INFECTIONS

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📌 8. LABORATORY DIAGNOSIS OF VIRAL INFECTIONS

Methods in Table:

Cytopathic Effect (CPE) — [Damage visible in cell cultures]:

Virus infects cell culture
        ↓
Cells show changes:
• Cell lysis (death) / rounding
• Syncytia formation (cells fuse together) — e.g., Measles, RSV
• Inclusion bodies (abnormal deposits inside cells)
• Plaque formation (clear areas in cell sheet)

Serology Interpretation Table:

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📌 9. MEDICAL MANAGEMENT OF VIRAL INFECTIONS

A. Antiviral Drugs:

B. Supportive Treatment:

• Antipyretics (Paracetamol) for fever
• IV fluids for dehydration
• Oxygen for respiratory distress
• Nutrition support
• Pain management

⚠️ IMPORTANT: Antibiotics DO NOT work against viruses. Using antibiotics unnecessarily causes resistance. Nurses must educate patients about this.

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📌 10. NURSING MANAGEMENT (Detailed)

A. Assessment:

• Take full history — onset, duration, contact with sick persons
• Assess vital signs — especially temperature (fever pattern)
• Check for rash, lymph node enlargement, respiratory distress
• Note vaccination history

B. Nursing Diagnoses:

1. Hyperthermia related to viral infection
2. Ineffective airway clearance related to respiratory viral infection
3. Fluid volume deficit related to vomiting/diarrhea
4. Risk for infection transmission related to communicable viral disease
5. Deficient knowledge related to viral illness and prevention

C. Nursing Interventions Table:

D. Isolation Precautions for Viral Diseases:

E. Hand Hygiene Protocol:

Before patient contact
        ↓
Before aseptic procedure
        ↓
After body fluid exposure
        ↓
After patient contact
        ↓
After touching patient environment
(WHO 5 Moments of Hand Hygiene)

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📌 11. IMPORTANT VIRAL DISEASES — QUICK SUMMARY

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📌 12. COMPLICATIONS OF VIRAL INFECTIONS

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📌 13. PREVENTION OF VIRAL INFECTIONS

A. Vaccination (Active Immunization):

B. Other Prevention Methods:

Personal Protection:
• Hand hygiene (soap + water or alcohol sanitizer)
• PPE use (masks, gloves, gowns)
• Avoid contact with sick persons

Environmental Control:
• Disinfection of surfaces (especially for non-enveloped viruses)
• Sterilization of equipment
• Safe disposal of sharps/blood products

Vector Control:
• Mosquito nets, repellents (Dengue, Zika, Yellow fever)
• Rodent control (Hantavirus)

Blood Safety:
• Screen blood before transfusion (HIV, HBV, HCV)
• Use sterile needles only — never share needles

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📌 14. QUICK REVISION POINTS ⚡

1. Viruses are 20–300 nm in size — smallest infectious agents
2. Viruses contain ONLY ONE type of nucleic acid — either DNA or RNA (not both)
3. The complete virus particle is called a virion
4. The protein coat = Capsid | Capsid units = Capsomeres
5. Viruses with fat coat = Enveloped = sensitive to soap/alcohol
6. Viruses without fat coat = Naked/Non-enveloped = more resistant
7. Steps of replication: A-P-U-B-A-R (Attachment → Penetration → Uncoating → Biosynthesis → Assembly → Release)
8. IgM = acute infection | IgG = past infection/immunity
9. PCR = most sensitive method to detect viral nucleic acid
10. Inclusion bodies: Negri = Rabies | Guarnieri = Smallpox | Cowdry = Herpes
11. Antibiotics do NOT work against viruses
12. Retroviruses (HIV) use reverse transcriptase — RNA → DNA
13. Enveloped viruses spread via droplets, blood, secretions; non-enveloped via fecal-oral, fomites
14. Antigenic drift = small mutation (seasonal flu) | Antigenic shift = major genetic change (pandemic flu)
15. Latent viruses hide and reactivate: HSV, VZV (shingles), EBV

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📌 15. CLINICAL EXAMPLES

Case 1: Herpes Zoster (Shingles)

• Isolate patient (airborne + contact precautions)
• Administer Acyclovir (antiviral) as prescribed
• Manage pain (analgesics, gabapentin for nerve pain)
• Prevent scratching; keep skin clean
• Educate: rash is contagious to those who never had chickenpox

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Case 2: Dengue Fever

• Monitor vitals every 2–4 hours; watch for signs of shock
• Monitor platelet count and hematocrit daily
• IV fluids as prescribed (avoid over-hydration)
• Avoid aspirin/NSAIDs (increase bleeding risk) — give only paracetamol
• Watch for warning signs: abdominal pain, bleeding, restlessness
• No specific antiviral — management is supportive

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📌 16. EXAM WRITING FORMAT

For a 5-Mark Answer: "Classification of Viruses"

• Based on nucleic acid: DNA viruses vs RNA viruses (table with examples)
• Based on capsid shape: Icosahedral / Helical / Complex
• Based on envelope: Enveloped vs Non-enveloped

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For a 10-Mark Answer: "Describe the Structure, Replication, and Pathogenesis of Viruses"

1. Introduction — Definition, size, importance
2. Structure — Diagram + components explained (capsid, envelope, glycoprotein spikes)
3. Classification — Brief table (DNA/RNA; enveloped/non-enveloped)
4. Replication — Flowchart (APUBAR steps)
5. Pathogenesis — Types of infection (acute, chronic, latent); how viruses cause cell damage
6. Lab Diagnosis — PCR, ELISA, cell culture, inclusion bodies
7. Conclusion — Clinical significance

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📌 17. PRACTICE QUESTIONS

LONG QUESTIONS (10 marks each):

1. Describe the structure of a virus with a neat labeled diagram. Classify viruses based on nucleic acid type and envelope, giving examples of each.
2. Explain the replication cycle of a virus with a flowchart. How does the replication strategy differ between DNA and RNA viruses?
3. Describe the pathogenesis of viral infections. Explain the different types of viral infections with examples.
4. Write in detail about the laboratory diagnosis of viral infections. Include methods of antigen detection, serology, and molecular techniques.
5. Explain the nursing management of a patient with a viral fever. Include assessment, nursing diagnoses, interventions, and patient education.

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SHORT QUESTIONS (5 marks each):

1. Write a note on the Baltimore Classification of viruses.
2. Describe cytopathic effects (CPE) in viral diagnosis.
3. Explain the difference between enveloped and non-enveloped viruses with nursing relevance.
4. Write about antiviral drugs with mechanism of action and nursing considerations.
5. Explain viral latency with two examples.

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VERY SHORT QUESTIONS (2 marks each):

1. Define virion.
2. What is a capsid?
3. What does PCR stand for? What does it detect?
4. Define antigenic drift and antigenic shift.
5. Name two RNA viruses and two DNA viruses.
6. What is cytopathic effect (CPE)?
7. Name the inclusion bodies seen in Rabies and Smallpox.
8. What is a retrovirus? Give one example.
9. State the difference between IgM and IgG in serology.
10. Name the precautions used for airborne viral infections.

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MCQs (with Answer Key):

• A) Capsid
• B) Virion ✅
• C) Nucleocapsid
• D) Capsomere

• A) Have both DNA and RNA
• B) Replicate by binary fission
• C) Contain only ONE type of nucleic acid ✅
• D) Can grow on artificial media

• A) Flaviviridae
• B) Herpesviridae
• C) Retroviridae ✅
• D) Paramyxoviridae

• A) Uncoating
• B) Biosynthesis
• C) Attachment ✅
• D) Assembly

• A) Smallpox
• B) Herpes
• C) Rabies ✅
• D) Chickenpox

• A) Influenza virus
• B) Herpes Simplex Virus ✅
• C) Rotavirus
• D) Poliovirus

• A) Acyclovir
• B) Oseltamivir
• C) Amoxicillin ✅
• D) Ribavirin

• A) Past immunity
• B) Vaccination response
• C) Acute/recent infection ✅
• D) Chronic carrier state

• A) Anopheles mosquito
• B) Culex mosquito
• C) Aedes mosquito ✅
• D) Sandfly

• A) Measles virus
• B) Varicella-Zoster Virus ✅
• C) Rubella virus
• D) Cytomegalovirus

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📌 18. ANSWER KEY

Very Short Questions:

1. Virion = complete, fully formed virus particle outside the host cell
2. Capsid = protein shell/coat that protects viral nucleic acid
3. PCR = Polymerase Chain Reaction; detects viral DNA/RNA (molecular method)
4. Antigenic drift = small mutation in surface proteins (seasonal flu); Antigenic shift = major genetic reassortment (pandemic flu)
5. RNA viruses: HIV, Influenza | DNA viruses: Herpes simplex, Hepatitis B
6. CPE = visible changes (damage/death) in host cells caused by viral infection in cell culture
7. Negri bodies = Rabies | Guarnieri bodies = Smallpox
8. Retrovirus = virus using reverse transcriptase to convert RNA → DNA; Example: HIV
9. IgM = acute/recent infection | IgG = past infection or immunity
10. Airborne precautions — N95 mask, negative pressure room, door kept closed

MCQ Answers:

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📌 SOURCES

• Jawetz, Melnick & Adelberg's Medical Microbiology, 28th Edition
• Medical Microbiology, 9th Edition (Murray)
• Sherris & Ryan's Medical Microbiology, 8th Edition

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Study Tip: Read once slowly. Then cover and recall using Quick Revision Points. Practice MCQs at the end. These notes replace the textbook for revision — everything important is here. Good luck! 🌟