1. Classification - Alpha (HSV-1/2, VZV), Beta (CMV, HHV-6/7), Gamma (EBV, KSHV)
2. HSV-1 vs HSV-2 - HSV-1 = orofacial (cold sores, gingivostomatitis, encephalitis); HSV-2 = genital herpes + neonatal herpes
3. Lab Dx of HSV - PCR (best), culture, Tzanck smear (multinucleated giant cells), DFA, type-specific serology
4. VZV pathogenesis - Respiratory entry → primary viremia (lymph nodes) → secondary viremia (liver/spleen) → skin (vesicles); latency in dorsal root ganglia
5. Neonatal vs Congenital varicella - Neonatal = perinatal exposure (severe, fatal); Congenital = 1st/2nd trimester (limb hypoplasia, microcephaly, cicatrix)
6. Ramsay Hunt - VZV reactivation in geniculate ganglion; triad: otalgia + ear vesicles + facial palsy; treat with steroids + antivirals
7. Lab Dx of VZV - Clinical diagnosis usually sufficient; FAMA test is gold standard for immunity; PCR for atypical cases; Tzanck smear
8. Immunoprophylaxis VZV - Live attenuated vaccine (Oka strain, 2 doses); VariZIG for high-risk post-exposure
9. CMV infections - Congenital (owl-eye inclusions, microcephaly, IUGR); CMV mono (heterophil-negative); immunocompromised: retinitis, pneumonia, colitis; treat with ganciclovir
10. EBV infections - Infectious mono (fever + pharyngitis + lymphadenopathy + atypical lymphocytes + heterophil antibodies); associated with Burkitt lymphoma, NPC, Hodgkin's
11. Roseola infantum - HHV-6B; ages 6mo-4yr; high fever 3-5 days → sudden defervescence → macular rash; febrile seizures possible; self-limited

HERPES VIRUSES - Complete Notes

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1. Classification of Herpes Viruses

• dsDNA, icosahedral capsid, enveloped
• Establish lifelong latency after primary infection
• Can reactivate (symptomatic or asymptomatic)
• All produce intranuclear inclusion bodies (Cowdry type A)
• All alphaherpesviruses are neurotropic (latency in sensory ganglia)

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2. Infections Caused by HSV-1 and HSV-2

• Herpes labialis - "cold sores"; vesicles at vermillion border; reactivation from trigeminal ganglion
• Primary herpetic gingivostomatitis - erythematous bleeding gums, painful vesicles throughout oral cavity
• Herpetic keratoconjunctivitis - dendritic corneal ulcers; ophthalmic emergency
• Herpes encephalitis - most common cause of sporadic fatal encephalitis; temporal lobe involvement
• Eczema herpeticum - life-threatening vesicular eruption on pre-existing eczema skin; treat with IV acyclovir
• Herpetic whitlow - infection of distal finger by autoinoculation

• Genital herpes - painful vesicles/ulcers on genitalia; frequent recurrences
• Neonatal herpes - acquired during vaginal delivery; can be disseminated, CNS, or skin/eye/mouth (SEM) type
• Herpes meningitis - recurrent benign lymphocytic meningitis (Mollaret's)
• Sacral radiculopathy - urinary retention, constipation

• Asymptomatic viral shedding (major source of transmission)
• Disseminated disease in immunocompromised/neonates
• Latency in sensory ganglia (trigeminal for HSV-1, sacral for HSV-2)

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3. Lab Diagnosis of HSV Infections

• For herpes encephalitis: CSF PCR is the method of choice
• For ocular herpes: Slit lamp + fluorescein staining shows dendritic ulcers

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4. Pathogenesis of Chickenpox (Varicella)

1. Entry - VZV inhaled; infects mucosal cells of upper respiratory tract/conjunctiva
2. Primary viremia - Replication in regional lymph nodes → enters bloodstream
3. Visceral replication - Virus replicates in liver and spleen
4. Secondary viremia - Infected mononuclear cells transport virus to skin and respiratory mucosa
5. Rash formation - Swelling of epithelial cells, ballooning degeneration, tissue fluid accumulation → vesicle formation
6. Immune response - Humoral + cellular immunity + interferon terminate infection
7. Latency - Virus establishes latency in trigeminal and dorsal root ganglia
8. Reactivation - If immunity wanes → herpes zoster (shingles)

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5. Neonatal Varicella / Congenital Varicella

• Mother develops chickenpox 5 days before to 2 days after delivery
• Infant receives no protective maternal IgG (insufficient time for transplacental transfer)
• Leads to severe, disseminated disease - pneumonia, hepatitis, DIC; can be fatal
• Management: VariZIG to neonate immediately; IV acyclovir if disease develops

• Mother infected during 1st-2nd trimester (highest risk: weeks 8-20)
• Risk of CVS: approximately 2% of primary infections in first 20 weeks

• Skin: cicatricial (zigzag) scarring in dermatomal distribution
• Limb: hypoplasia, atrophy
• Eye: chorioretinitis, cataracts, microphthalmia
• CNS: microcephaly, cortical atrophy, mental retardation, seizures
• IUGR (intrauterine growth retardation)

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6. Ramsay Hunt Syndrome

1. Otalgia - severe pain in and around the ear
2. Herpetic vesicles - on the pinna, external auditory canal (herpes zoster oticus)
3. Peripheral facial palsy - lower motor neuron facial nerve palsy (resembles Bell's palsy)

• SNHL, tinnitus, and vestibular symptoms in up to 50% of patients
• Cranial nerves V, IX, X, XI, XII may also be affected
• Incidence: ~30 per 100,000 persons

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7. Lab Diagnosis of Chickenpox (VZV)

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8. Immunoprophylaxis of Chickenpox

• Live attenuated varicella vaccine (Oka strain): Approved 1995; 2 doses (12-15 months + 4-6 years); also available as MMRV
• Zoster vaccine - Shingrix (recombinant subunit): Adults ≥50 years; 2 doses 2-6 months apart; highly effective against shingles and postherpetic neuralgia
• Zoster vaccine - Zostavax (live attenuated): Adults ≥60 years; being phased out in favour of Shingrix

• VariZIG (Varicella-Zoster Immune Globulin): Post-exposure prophylaxis for high-risk seronegative individuals; given within 10 days of exposure; modifies but may not prevent infection
• Standard IVIG: Low VZV antibody titer; generally not effective for VZV prophylaxis

• Immunocompromised seronegative patients
• Seronegative pregnant women
• Neonates of mothers with perinatal varicella
• Premature infants <28 weeks

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9. Infections Caused by Cytomegalovirus (CMV)

• Usually asymptomatic
• CMV mononucleosis - heterophil-negative mono; fever, malaise, fatigue, mild hepatitis; self-limited; accounts for 20-50% of heterophil-negative mono cases

• CMV retinitis - "pizza pie" fundus; leading cause of blindness in AIDS (CD4 <50)
• CMV pneumonitis - interstitial pneumonia; most common in bone marrow transplant recipients
• CMV colitis - bloody diarrhea, abdominal pain
• CMV hepatitis, encephalitis
• Post-transplant complications: leukopenia, obliterative bronchiolitis (lung Tx), graft atherosclerosis (heart Tx)

• ~1% of live births in USA; ~5-10% of those develop severe disease
• Features: microcephaly, periventricular calcifications, IUGR, jaundice, hepatosplenomegaly, thrombocytopenic purpura ("blueberry muffin baby"), chorioretinitis, SNHL
• Mortality ~20%; survivors: mental retardation, deafness, ocular defects
• Even subclinical congenital CMV → deafness in ~10%

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10. Infections Caused by Epstein-Barr Virus (EBV)

• Incubation: 30-50 days
• Transmission: oropharyngeal secretions (saliva)
• Classic triad: Fever + Exudative pharyngitis + Lymphadenopathy (especially posterior cervical)
• Splenomegaly (50-60%), hepatitis, maculopapular rash (especially with ampicillin/amoxicillin)
• Atypical lymphocytes (Downey cells) on blood smear - large reactive T cells
• Heterophil antibodies (agglutinate sheep/horse RBCs) - detected by Monospot test
• Self-limited: 2-4 weeks
• Complications: splenic rupture, airway obstruction, hemolytic anemia, thrombocytopenia

• Burkitt lymphoma - B cell lymphoma; jaw tumor in African children; >90% contain EBV DNA; t(8;14) c-myc translocation; malaria = cofactor
• Nasopharyngeal carcinoma - epithelial cancer; common in Chinese/Southeast Asian males; EBNA1 + LMP1 expressed
• Hodgkin's lymphoma (mixed cellularity subtype)
• Post-transplant lymphoproliferative disorder (PTLD)
• Non-Hodgkin lymphoma in AIDS

• Monospot test (heterophil agglutination)
• EBV serology:
  • VCA-IgM = current/acute infection
  • VCA-IgG = past infection (persists for life)
  • EA (early antigen) antibodies = active viral replication
  • EBNA antibodies = appear weeks after acute infection, persist for life (absence = recent primary infection)

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11. Roseola Infantum (Exanthem Subitum)

• Child appears relatively well despite high fever
• Febrile seizures are a recognized complication
• Leukopenia during febrile phase
• Virus establishes latency in monocytes/macrophages and salivary glands

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Latency and Reactivation - Simple Language

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🦠 What is Latency?

The virus enters your body, causes disease, then HIDES inside your nerve cells and goes to SLEEP.

• After the first infection (primary infection), your immune system fights the virus
• But the virus is smart - it hides inside nerve cells (neurons) where the immune system cannot kill it
• Inside the nerve cell, the virus stops replicating - it just sits there quietly doing nothing
• This "sleeping" state is called LATENCY
• The virus stays there FOR LIFE - you can never fully get rid of it

Where does each virus hide (latency site)?

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⚡ What is Reactivation?

When the sleeping virus "wakes up" and causes disease again.

What happens during reactivation?

1. Virus wakes up inside the nerve cell
2. Starts replicating again
3. Travels down the nerve to the skin
4. Causes vesicles (blisters) in that nerve's area of skin
5. This is why shingles appears in a stripe/band - follows one nerve!

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Simple Analogy 🏠

Think of the virus like a criminal hiding in your house basement.

• Police (immune system) fought the criminal during the first attack
• Criminal couldn't escape so hid in the basement (nerve cell)
• When police are strong - criminal stays hidden (latency)
• When police are weak (stress/illness/old age) - criminal comes out and attacks again (reactivation)

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Latency vs Reactivation - Quick Table

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Chickenpox Rash - Real Photo

• Multiple red spots scattered on the trunk (abdomen area)
• Different sizes - some small red dots, some larger with a central vesicle
• This is the early stage - spots start on trunk before spreading to face and limbs
• Later these become fluid-filled vesicles ("dewdrop on rose petal") then crust over

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The Full Story of VZV - Primary → Latency → Reactivation

Child breathes in VZV
        ↓
Gets CHICKENPOX (primary infection)
        ↓
Immune system fights it - rash heals
        ↓
But virus HIDES in dorsal root ganglia (LATENCY)
        ↓
Person lives normally for decades
        ↓
At age 60-70, immunity weakens
        ↓
Virus WAKES UP (REACTIVATION)
        ↓
Travels down nerve to skin
        ↓
Causes SHINGLES (painful rash in a band/stripe)

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• 1st time = Chickenpox (widespread rash, child)
• Reactivation = Shingles/Herpes Zoster (band-like painful rash, elderly/immunocompromised)

Lab Diagnosis of HSV - Step by Step

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🧪 SPECIMENS COLLECTED

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STEP 1 - DIRECT EXAMINATION (Fastest, done first)

🔬 Tzanck Smear

• Scrape the base of a fresh vesicle
• Smear on glass slide
• Stain with Giemsa or Wright stain
• See under microscope

⚠️ This is POSITIVE in both HSV and VZV - cannot tell the difference between them

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STEP 2 - VIRAL CULTURE (Gold Standard for active lesion)

• Take vesicle fluid or swab
• Inoculate into human diploid fibroblast cell line
• Incubate and observe for CPE (cytopathic effect)

• Rounding and clumping of cells
• CPE appears within 24-48 hours (HSV spreads fast in culture)

✅ Gold standard for active lesions ❌ Slow, not used for encephalitis

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STEP 3 - PCR (Most Sensitive & Specific)

• Take specimen (CSF, vesicle fluid, swab)
• Amplify HSV DNA using PCR

• Herpes encephalitis → CSF PCR = METHOD OF CHOICE
• Atypical cases, immunocompromised patients
• Can differentiate HSV-1 from HSV-2

✅ Most sensitive and specific ✅ Best for CNS infection ✅ Can be done even when culture is negative

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STEP 4 - ANTIGEN DETECTION (Quick, Specific)

Direct Fluorescent Antibody (DFA)

• Smear vesicle scraping on slide
• Apply fluorescent-labeled anti-HSV antibodies
• View under fluorescent microscope

✅ Faster than culture ✅ Can distinguish HSV-1 from HSV-2 ✅ More specific than Tzanck

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STEP 5 - SEROLOGY (For past infection / epidemiology)

• Take blood sample
• Detect HSV-specific antibodies by ELISA

⚠️ NOT useful for diagnosing acute active infection ✅ Useful for screening, epidemiology, partner counselling

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STEP 6 - HISTOPATHOLOGY (Biopsy / Post mortem)

• Tissue biopsy stained with H&E
• See Cowdry type A intranuclear inclusions (eosinophilic inclusions surrounded by halo)
• Multinucleated giant cells

Used in encephalitis brain biopsy, post mortem cases

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🗂️ SUMMARY TABLE

SPECIMEN COLLECTED
      ↓
┌─────────────────────────────────────────┐
│  STEP 1: Tzanck smear                   │
│  (Quick, cheap, not specific)           │
├─────────────────────────────────────────┤
│  STEP 2: Viral Culture                  │
│  (Gold standard - active skin lesion)   │
├─────────────────────────────────────────┤
│  STEP 3: PCR                            │
│  (Best for CSF/encephalitis)            │
├─────────────────────────────────────────┤
│  STEP 4: DFA                            │
│  (Rapid antigen detection)              │
├─────────────────────────────────────────┤
│  STEP 5: Serology                       │
│  (Past infection / epidemiology)        │
├─────────────────────────────────────────┤
│  STEP 6: Histopathology                 │
│  (Biopsy / post mortem)                 │
└─────────────────────────────────────────┘

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🎯 WHICH TEST TO USE WHEN?

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🔑 EXAM POINTS

• Tzanck smear → multinucleated giant cells → positive in BOTH HSV and VZV
• Culture → gold standard for skin lesion → CPE in 24-48 hrs
• PCR → method of choice for encephalitis (CSF)
• DFA → rapid, distinguishes HSV-1 from HSV-2
• Cowdry type A inclusions → seen in histopathology
• Serology NOT useful for acute diagnosis

Lab Diagnosis of Chickenpox (VZV) - Step by Step

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🧪 SPECIMENS COLLECTED

⚠️ Important: Collect specimen from fresh vesicle (not crusted lesion - virus dies as vesicle crusts over)

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STEP 1 - CLINICAL DIAGNOSIS (Most Common in Practice)

In a typical case, no lab test is needed - diagnosis is made clinically!

• Successive crops of rash (macule → papule → vesicle → crust)
• All stages present simultaneously on the body
• Starts on trunk → spreads to face and limbs
• Palms and soles spared
• "Dewdrop on rose petal" appearance of vesicle
• Mild fever, itching

✅ In a normal healthy child with classic rash → clinical diagnosis is enough ❌ Lab tests needed only in atypical cases, immunocompromised, or complications

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STEP 2 - TZANCK SMEAR (Quick Bedside Test)

• Scrape the base of a fresh vesicle
• Smear on glass slide
• Stain with Giemsa stain
• View under microscope

• Multinucleated giant cells
• Intranuclear inclusions (Cowdry type A)

⚠️ POSITIVE in both VZV and HSV - cannot distinguish between the two ✅ Quick, cheap, bedside test

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STEP 3 - DIRECT FLUORESCENT ANTIBODY TEST (DFA)

• Scrape vesicle base
• Apply fluorescent-labeled anti-VZV antibodies on slide
• View under fluorescent microscope

✅ More specific than Tzanck ✅ Distinguishes VZV from HSV (unlike Tzanck) ✅ Quick result (few hours)

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STEP 4 - PCR (Most Sensitive & Specific)

• Take vesicle fluid / CSF / blood
• Amplify VZV DNA

• Immunocompromised patients (atypical rash)
• VZV encephalitis / meningitis → CSF PCR
• Congenital varicella → amniotic fluid PCR
• Disseminated disease

✅ Most sensitive and specific ✅ Method of choice for CNS involvement ✅ Can confirm diagnosis when rash is atypical

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STEP 5 - VIRAL CULTURE (Rarely Done)

• Inoculate vesicle fluid into human embryonic cell line
• Observe for CPE

• Focal CPE (spreads slowly - unlike HSV)
• Intranuclear inclusion bodies

❌ Technically very difficult ❌ VZV is strongly cell-associated - very little free virus in fluid ❌ Spreads slowly (takes weeks) ❌ Rarely performed in clinical practice

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STEP 6 - SEROLOGY (For Immunity Testing)

FAMA Test (Fluorescent Antibody to Membrane Antigen)

• Patient blood taken
• Detects VZV-specific antibodies against membrane antigens

✅ Gold standard for detecting VZV immunity ✅ Used to check if vaccine worked ✅ Used for post-exposure screening (is this person immune?) ❌ Not readily available everywhere

ELISA / Complement Fixation

• Detects rising antibody titers (compare acute + convalescent serum)
• 4-fold rise in titer = confirms recent infection

✅ Widely available ✅ Useful for confirming past infection or immunity

What Serology Tells You:

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STEP 7 - HISTOPATHOLOGY (Biopsy)

• Skin biopsy stained with H&E
• See Cowdry type A intranuclear inclusions
• Multinucleated giant cells
• Ballooning degeneration of epidermal cells

Used in atypical cases, immunocompromised, or post mortem

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🗂️ SUMMARY TABLE

SPECIMEN COLLECTED (fresh vesicle fluid/scraping)
              ↓
┌──────────────────────────────────────────────┐
│ STEP 1: Clinical Diagnosis                   │
│ (Sufficient in typical cases)                │
├──────────────────────────────────────────────┤
│ STEP 2: Tzanck Smear                         │
│ (Quick - multinucleated giant cells)         │
│ Cannot distinguish VZV from HSV              │
├──────────────────────────────────────────────┤
│ STEP 3: DFA Test                             │
│ (Rapid, specific - distinguishes VZV/HSV)    │
├──────────────────────────────────────────────┤
│ STEP 4: PCR                                  │
│ (Best for CNS/immunocompromised/atypical)    │
├──────────────────────────────────────────────┤
│ STEP 5: Viral Culture                        │
│ (Rarely done - technically difficult)        │
├──────────────────────────────────────────────┤
│ STEP 6: Serology                             │
│ FAMA = Gold standard for immunity            │
│ ELISA = Widely available                     │
├──────────────────────────────────────────────┤
│ STEP 7: Histopathology                       │
│ (Cowdry type A inclusions - biopsy)          │
└──────────────────────────────────────────────┘

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🎯 WHICH TEST TO USE WHEN?

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🔑 EXAM POINTS

• Clinical diagnosis is sufficient in typical cases
• Tzanck smear → multinucleated giant cells → positive in BOTH VZV and HSV (not specific)
• DFA → distinguishes VZV from HSV
• PCR → method of choice for CNS/atypical/immunocompromised
• Viral culture → rarely done (cell-associated virus, spreads slowly)
• FAMA test → gold standard for detecting VZV immunity
• Fresh vesicle = best specimen (not crusted lesion)