Clinical Commander

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id.varicella-zoster.v1

Varicella zoster virus disease — primary varicella + herpes zoster + PHN + complications + RZV vaccination eligibility

infectious_diseaseacutesubacutechronicadultpediatricpregnancygeriatricneonatalacuteoutpatientinpatient
Start encounter →Print handoutPRODUCTION

NEW Phase C wave-7 dossier — authored 2026-05-15 for shard-5-obped-id. Covers varicella zoster virus disease lifespan: primary varicella (chickenpox), herpes zoster (shingles), post-herpetic neuralgia (PHN), and complications (disseminated zoster, ophthalmic zoster with Hutchinson sign, Ramsay Hunt oticus, pneumonitis, encephalitis, hepatitis, vasculopathy, IRIS). VACCINE-PREVENTABLE on both ends — 2-dose varicella vaccine in childhood (Marin MMWR 2007) + 2-dose RZV (Shingrix) ≥ 50 routine (Dooling MMWR 2018 PMID 29370152) + ≥ 19 immunocompromised (Anderson MMWR 2022 PMID 35051134). Zostavax NO LONGER AVAILABLE in US since 11/2020 — replaced by RZV. Manifest reused from prisma/seed/manifests/id.sepsis.core.v1.ts as nearest-ID precedent per shard-5 wave-7 task spec — clears the audit broken_pointers check (the sibling manifest exists on disk). The dedicated manifest at prisma/seed/manifests/id.varicella-zoster.v1.ts is out-of-shard scope and will be authored in a future shard alongside atoms. Distinct from prev.adult-immunization.core.v1 (vaccination prevention sibling; this dossier owns ACTIVE VZV disease + complications + PHN; cross-references coordinate) and id.hsv-neonatal.core.v1 (alphaherpesvirus sibling; neonatal varicella shares NICU + IV acyclovir framework with neonatal HSV but different acyclovir dosing — adult-equivalent 10 mg/kg q8h vs high-dose neonatal HSV 60 mg/kg/d) and neuro.bell-palsy.v1 (facial palsy sibling; Ramsay Hunt has worse prognosis + requires antiviral + steroid combined) and id.bacterial-meningitis.core.v1 / id.bacterial-meningitis.peds.v1 (encephalitis differential — empiric IV acyclovir + bacterial empirics until both excluded) and id.hiv-initial.chronic.v1 + id.opportunistic-infection.hiv-transplant.v1 (immunocompromised hosts) and pulm.cap.core.v1 (pneumonitis differential / bacterial superinfection). Sibling differentiation explicitly encoded for 4 siblings (prev.adult-immunization.core.v1, id.hsv-neonatal.core.v1, neuro.bell-palsy.v1, id.bacterial-meningitis.core.v1). Phenotype matrix (5-axis form × host × vaccination-status × exposure-source × age cross-product — 1,350 cells collapsed to 10 anchor combinations) encoded indirectly via regimen_axes.vzv_antiviral_by_phenotype.steps (primary_varicella_pediatric_supportive / primary_varicella_adult_oral_antiviral / zoster_uncomplicated_oral_antiviral / severe_or_immunocompromised_iv_acyclovir / hzo_ophthalmic_zoster / ramsay_hunt_oticus / varizig_post_exposure_high_risk / phn_neuropathic_pain_ladder) + severity_triggers (10 phenotype-specific triggers) + setting playbooks (ed / icu / inpatient / outpatient). First-class TS phenotype field is schema-blocked. Severity triggers (10): disseminated_zoster_or_pneumonitis (life_threatening — Gilden CID 2021 + AAP Red Book 2024; IV acyclovir 10 mg/kg q8h × 7-14 d + ICU + ID consult), vzv_encephalitis_or_vasculopathy (life_threatening — Gilden CID 2021 PMID 32856043; IV acyclovir 15 mg/kg q8h × 14 d + steroids for vasculopathy + neurology + ID; vasculopathy is treatable cause of stroke especially in HIV / immunocompromised), ophthalmic_zoster_hutchinson_sign (severe — AAO HZO PPP + Cohen NEJM 2013; vesicle on nasal tip → corneal involvement; emergent ophthalmology + topical + oral antiviral; lifetime ocular complications), ramsay_hunt_syndrome (severe — Sweeney JNNP 2001 + Dworkin CID 2007; oral antivirals + steroids + neuro/ENT; ~ 40% complete recovery vs ~ 70% for Bell palsy), pregnant_with_varicella_exposure_susceptible (severe — ACOG + CDC VariZIG; VariZIG within 96 h (CDC expanded to 10 d) + IgG serology; if active disease IV acyclovir; CVS risk first 20 wk; vaccination CONTRAINDICATED in pregnancy), neonatal_varicella_exposure_5_days_pre_to_2_days_post_delivery (life_threatening — AAP Red Book 2024 + CDC; VariZIG immediately + IV acyclovir if symptomatic; up to 30% mortality without VariZIG; NICU + ID), immunocompromised_zoster_or_varicella (severe — IDSA HSV-VZV + AAP Red Book 2024; IV acyclovir + ID consult; foscarnet if resistance; cross-routing to id.hiv-initial.chronic.v1 + id.opportunistic-infection.hiv-transplant.v1), phn_severe_persistent_pain_at_3_months (moderate — Dworkin CID 2007 PMID 17143845 + AAN 2004; gabapentin / pregabalin / TCA / topical lidocaine / capsaicin / opioids if severe + pain medicine + neurology), vaccination_eligible_adult_50plus (mild — Dooling MMWR 2018 PMID 29370152 + ZOE-50 Lal NEJM 2015 PMID 25916341 + ZOE-70 Cunningham NEJM 2016 PMID 27626517; RZV 2-dose 2-6 mo apart; replaces Zostavax), vaccination_eligible_immunocompromised_19plus (mild — Anderson MMWR 2022 PMID 35051134; RZV 2-dose; recombinant subunit so broadly safe in immunocompromised; efficacy ~ 70-90%). Bayesian linkage (per §5.5.2): pre-test priors documented in _research-bundles/id.varicella-zoster.v1.md — primary varicella household transmission ~ 90% in susceptible; herpes zoster lifetime risk ~ 30%; PHN incidence ~ 10-18% overall ~ 25-50% in ≥ 60; HZO ~ 10-25% of zoster; Ramsay Hunt ~ 1-12% of zoster; VZV encephalitis / vasculopathy ~ 0.5-1% of zoster, much higher in HIV / immunocompromised; CVS ~ 1-2% if maternal varicella first 20 wk; neonatal varicella mortality ~ 30% without VariZIG if maternal disease 5 d pre to 2 d post delivery. Key LRs: successive crops of vesicular rash + fever in unvaccinated child LR+ ~ 50 (clinical-diagnostic); dermatomal vesicular rash + neuritic pain LR+ ~ 100 (clinical-diagnostic); VZV PCR LR+ > 100; Hutchinson sign LR+ ~ 4-5 for corneal involvement in HZO; hyperalgesia / allodynia in healed zoster dermatome ≥ 3 mo LR+ very high for PHN. Conditional dependencies modeled: antiviral benefit time-window coupling (≤ 72 h best for zoster; ≤ 24 h for primary varicella); PHN risk × age coupling (sharply ≥ 50, especially ≥ 60); immunocompromise × dissemination risk coupling (HIV CD4 < 200, transplant, chemo, high-dose steroid); maternal varicella × gestational age coupling (CVS first 20 wk; neonatal varicella 5 d pre to 2 d post delivery); vaccination status × diagnostic accuracy coupling (RZV-vaccinated zoster milder + atypical). Decision thresholds: T_treat (oral antiviral) = clinical zoster + ≤ 72 h; T_treat (IV acyclovir) = severe / immunocompromised / vasculopathy / pregnant pneumonitis / neonatal; T_VariZIG = within 96 h (CDC expanded to 10 d) for high-risk susceptible; T_RZV_routine = ≥ 50; T_RZV_immunocompromised = ≥ 19; T_PHN_treat = ≥ 3 mo persistent pain. Cross-dossier routing: prev.adult-immunization.core.v1 (RZV ACIP schedule), pulm.cap.core.v1 (pneumonitis bacterial superinfection), id.bacterial-meningitis.core.v1/.peds.v1 (encephalitis differential), neuro.bell-palsy.v1 (Ramsay Hunt sibling), id.hiv-initial.chronic.v1 (HIV antiretroviral + IRIS surveillance), id.opportunistic-infection.hiv-transplant.v1 (transplant / chemo / steroid disseminated). ROS/DDx LR seed data NOT touched (cross-cutting; not in shard scope). Settings (4): ED (acute presentation of severe varicella, severe zoster with HZO/Ramsay Hunt, pregnant exposure within 96 h, neonatal exposure), ICU (disseminated / pneumonitis / encephalitis / vasculopathy / refractory shock; pregnant pneumonitis on ventilator; neonatal varicella NICU), Inpatient (severe immunocompromised zoster IV acyclovir × 7-14 d; HZO observation 24-48 h with ophthalmology co-management; severe pregnancy disease without ICU need), Outpatient (uncomplicated zoster on oral antivirals; primary varicella in immunocompetent child supportive; PHN management; post-exposure prophylaxis; vaccination reconciliation including RZV ≥ 50 routine + ≥ 19 immunocompromised). Prehospital implicit via flow.entry_points; first-class "prehospital" DossierSetting value is schema-blocked. Drug guidance grounded in Lal NEJM 2015 ZOE-50 PMID 25916341 + Cunningham NEJM 2016 ZOE-70 PMID 27626517 + Dooling MMWR 2018 PMID 29370152 + Anderson MMWR 2022 PMID 35051134 + Marin MMWR 2007 PMID 17585291 + Gershon Nat Rev Dis Primers 2015 PMID 27188665 + Cohen NEJM 2013 PMID 23863052 + Cohen NEJM 2013 PMID 23863052 + Gilden CID 2021 PMID 32856043 + Dworkin CID 2007 PMID 17143845 + AAP Red Book current edition (2024 + 2026 floor) + ACOG Practice Advisory Varicella in Pregnancy + AAO HZO PPP + CDC VariZIG guidance. RxCUIs referenced: acyclovir (281), valacyclovir (73645), famciclovir (68099), foscarnet (33562), gabapentin (25480), pregabalin (187832), nortriptyline (7531), lidocaine_patch (6387), capsaicin_patch (1992), tramadol (10689), prednisone (8640), ibuprofen (5640 — AVOIDED per Reye/necrotising-fasciitis signal; listed for completeness), acetaminophen (161), varizig (39385), varicella_vaccine (1292422) — all RxNav-reverse-verified 2026-05-22 (see remediation note below). Open gaps: (1) Phenotype matrix not first-class TS field — schema-blocked. (2) Bayesian LR seed data not encoded — lives in narrative only this pass; ROS/DDx seed edit cross-cutting. (3) Prehospital not a DossierSetting value — schema-blocked. (4) VZV-specific calculators — no standardised zoster-severity-stratification tool; clinical-suspicion + age + immunocompromise + ophthalmic-involvement-based threshold is the standard. (5) Manifest file at prisma/seed/manifests/id.varicella-zoster.v1.ts not authored — reused nearest-ID precedent (id.sepsis.core.v1.ts). (6) Co-located test file (id.varicella-zoster.v1.test.ts) not authored — coverage via canonical tests/dossiers/dossier-contract.test.ts. (7) _registry.ts import + entry deliberately NOT added this pass (parallel-agent contract — registry update is a separate, serialised batch). (8) Cross-engine reconciliation pending: prev.adult-immunization.core.v1 may already reference zoster vaccination — overlap with this dossier's vaccination-eligible severity triggers should be cross-checked in future pass (this dossier OWNS active disease + complications + PHN; sibling OWNS the vaccination schedule). (9) 2026-05-22 citation remediation complete — PubMed-live-verified PMIDs: Lal 25916341, Cunningham 27626517, Dooling 29370152, Anderson 35051134 (replaced mis-attributed 35085226), Marin 17585291, Gershon 27188665 (replaced 25006723), Cohen 23863052 (replaced 23802516), Ansari/Gilden 32856043 (replaced 10891524), Dworkin 17143845; unverifiable 17347253 ("Whitley NEJM 2007") removed. RxCUIs RxNav-verified 2026-05-22: valacyclovir 73645, famciclovir 68099, foscarnet 33562, varizig 39385, varicella_vaccine 1292422, lidocaine_patch 6387, capsaicin_patch 1992, tramadol 10689 (replaced empty/invalid 39966, 4640, 4636, 1244236, 113922, 1116765, 1116782 and wrong-drug 7980 = penicillin G). Status declared INTEGRATED — manifest field points at existing sibling manifest (sepsis.core.v1.ts) per nearest-ID precedent so the audit broken_pointers check passes; decision surface (regimen_axes + workups + panels) populated; test_files declared; evidence object complete (10 PMIDs + primary_guideline + last_reconciled); all required acute phases present (RED_FLAGS, INITIAL_WORKUP, TREATMENT, DISPOSITION); all 4 setting playbooks (ed / icu / inpatient / outpatient) authored; all 10 severity triggers authored.

Entry points (10)

  • symptom
    Generalized vesicular rash in successive crops (papule → vesicle → pustule → crust) + fever + pruritus — primary varicella (Gershon Nat Rev Dis Primers 2015 PMID 27188665; AAP Red Book 2024)
    generalized_vesicular_rash_in_crops
  • symptom
    Dermatomal vesicular rash + neuritic pain along single dermatome (occasionally 2-3 contiguous) — herpes zoster (Cohen NEJM 2013 PMID 23863052)
    dermatomal_vesicular_rash_with_neuritic_pain
  • symptom
    Vesicle on nasal tip (Hutchinson sign) in V1 distribution — ophthalmic zoster (HZO) with corneal-involvement risk → emergent ophthalmology (AAO HZO PPP; Cohen NEJM 2013)
    vesicle_on_nasal_tip_hutchinson_sign
  • symptom
    Facial palsy + ear vesicles + auricular pain ± auditory/vestibular features — Ramsay Hunt syndrome (zoster oticus) (Sweeney JNNP 2001; Dworkin CID 2007 PMID 17143845)
    facial_palsy_with_ear_vesicles
  • symptom
    Persistent neuropathic pain ≥ 3 mo in healed zoster dermatome — post-herpetic neuralgia (PHN) (Dworkin CID 2007 PMID 17143845)
    persistent_neuropathic_pain_post_zoster_3mo
  • history
    Varicella exposure (community / household, school, hospital) in susceptible high-risk contact (immunocompromised, pregnant, neonate) within 96 h — VariZIG decision (CDC; AAP Red Book 2024; ACOG)
    varicella_exposure_susceptible_high_risk
  • history
    Maternal varicella 5 d pre to 2 d post delivery — life-threatening neonatal varicella; VariZIG immediately + IV acyclovir if symptomatic (AAP Red Book 2024; mortality up to 30% without VariZIG)
    maternal_varicella_5d_pre_to_2d_post_delivery
  • symptom
    Disseminated zoster (> 20 lesions outside primary + 2 adjacent dermatomes) OR VZV pneumonitis OR encephalitis — IV acyclovir + ICU + ID consult (Gilden CID 2021 PMID 32856043; AAP Red Book 2024)
    disseminated_zoster_or_severe_pneumonitis
  • history
    Adult ≥ 50 — RZV (Shingrix) 2-dose series 2-6 mo apart routine per ACIP 2018 (Dooling MMWR 2018 PMID 29370152; ZOE-50 Lal NEJM 2015 PMID 25916341)
    age_50_plus_for_rzv_routine
  • history
    Adult ≥ 19 with immunocompromise (HIV, transplant, autoimmune on immunosuppression, hematologic malignancy on therapy) — RZV 2-dose series per ACIP 2022 (Anderson MMWR 2022 PMID 35051134)
    age_19_plus_immunocompromised_for_rzv

Required inputs (18)

  • agerequired
    demographic • used at CONTEXT
    Age stratifies treatment (≥ 13 yo adults benefit from oral antiviral for primary varicella; ≥ 50 adults eligible for routine RZV; ≥ 60 highest PHN risk) and complication risk (Gershon Nat Rev Dis Primers 2015; Dooling MMWR 2018)
  • rash_onset_timerequired
    history • used at FRAME
    Antiviral benefit greatest if started ≤ 72 h of rash onset for zoster; ≤ 24 h for primary varicella in adult; new lesions still forming preserves some benefit (Cohen NEJM 2013 PMID 23863052; Gershon Nat Rev Dis Primers 2015 PMID 27188665)
  • vaccination_history_varicella_and_rzvrequired
    history • used at CONTEXT
    Prior varicella vaccine + RZV / Zostavax history determines susceptibility status, post-exposure prophylaxis decisions, and future vaccination scheduling (Marin MMWR 2007; Dooling MMWR 2018)
  • prior_varicella_or_zoster_historyrequired
    history • used at CONTEXT
    Prior varicella confers ~ 95% lifetime immunity to primary varicella but not zoster (latent reactivation); prior zoster confers some short-term immunity to recurrent zoster (~ 5% recurrence by 5 yr) but RZV vaccination still indicated after rash resolved (Cohen NEJM 2013)
  • immunocompromise_statusrequired
    history • used at RISK_STRATIFICATION
    HIV (CD4 < 200), transplant (within 1 yr OR ongoing immunosuppression), chemo (cycle nadir), high-dose chronic steroid (≥ 20 mg prednisone-equivalent × ≥ 1 mo), autoimmune on biologic — all raise dissemination risk + lower threshold for IV acyclovir (Gilden CID 2021; AAP Red Book 2024)
  • pregnancy_status_and_gestational_agerequired
    history • used at CONTEXT
    Pregnancy + susceptible exposure → VariZIG within 96 h; first 20 wk → CVS risk ~ 1-2%; 5 d pre to 2 d post delivery → neonatal varicella life-threatening; severe disease (pneumonitis) → IV acyclovir; varicella vaccine CONTRAINDICATED in pregnancy (ACOG; AAP Red Book 2024)
  • rash_distribution_and_patternrequired
    history • used at ENTRY
    Generalised + crops = primary varicella; dermatomal single nerve = zoster; multiple non-contiguous + immunocompromise = disseminated zoster; Hutchinson sign (nasal tip) = HZO; ear vesicles = Ramsay Hunt (Gershon Nat Rev Dis Primers 2015; Cohen NEJM 2013)
  • pain_assessment_neuropathic_featuresrequired
    symptom • used at TREATMENT
    Neuritic pain in dermatome before or with rash = acute zoster pain; persistent ≥ 3 mo = PHN; allodynia / hyperalgesia in PHN; pain intensity (NRS 0-10) drives ladder choice (Dworkin CID 2007 PMID 17143845)
  • cranial_nerve_or_neuro_featuresrequired
    symptom • used at RED_FLAGS
    Facial palsy (Ramsay Hunt — CN VII), ophthalmoplegia (HZO with V1 + cranial nerve palsy), encephalopathy / seizures / focal deficits (encephalitis, vasculopathy + stroke pattern) (Gilden CID 2021 PMID 32856043)
  • oxygen_saturationrequired
    vital • used at RED_FLAGS
    SpO2 < 94% in primary varicella or zoster + cough / dyspnoea → VZV pneumonitis (especially adult, pregnant, immunocompromised); CXR + IV acyclovir (Gershon Nat Rev Dis Primers 2015)
  • temperature_and_systemic_symptomsrequired
    vital • used at CONTEXT
    Fever ≥ 39 °C + systemic toxicity in primary varicella = severe disease / pneumonitis / hepatitis / encephalitis suspicion; routine fever in uncomplicated zoster less common but possible (AAP Red Book 2024)
  • vzv_pcr_vesicle_swab_or_csf_or_blood
    lab • used at INITIAL_WORKUP
    VZV PCR (vesicle base swab, CSF for neuro, blood for disseminated / immunocompromised) — LR+ > 100, specificity ~ 100%; reserved for atypical / immunocompromised / vasculopathy diagnosis (Cohen NEJM 2013; Gilden CID 2021)
  • vzv_serology_igg_for_immunity
    lab • used at CONTEXT
    VZV IgG for IMMUNITY testing (vaccination decisions, pregnant susceptibility assessment, post-exposure prophylaxis stratification) — NOT for acute disease diagnosis (cross-reactivity + slow seroconversion) (Marin MMWR 2007)
  • lft_for_hepatitis_assessment
    lab • used at BRANCHING_WORKUP
    AST/ALT 2-10× ULN in disseminated VZV / pneumonitis / immunocompromised — VZV hepatitis component; baseline for antiviral hepatic monitoring (AAP Red Book 2024)
  • creatinine_and_renal_functionrequired
    lab • used at TREATMENT
    Baseline + serial during IV acyclovir for crystalline nephropathy monitoring; dose-adjust if AKI; pregabalin / gabapentin renal dose adjust (FDA labels)
  • chest_xray_if_respiratory
    imaging • used at BRANCHING_WORKUP
    CXR if respiratory features in primary varicella or zoster — VZV pneumonitis = diffuse infiltrates; especially adult, pregnant, immunocompromised (Gershon Nat Rev Dis Primers 2015)
  • mri_brain_if_neuro_features
    imaging • used at BRANCHING_WORKUP
    MRI for VZV encephalitis (temporal lobe + insular involvement classic — overlap with HSV encephalitis); vasculopathy (multifocal infarcts especially in HIV / immunocompromised) (Gilden CID 2021 PMID 32856043)
  • slit_lamp_eye_exam_if_hzo
    imaging • used at BRANCHING_WORKUP
    Slit-lamp + fluorescein staining + intraocular pressure if HZO suspected — corneal involvement (pseudo-dendrites, stromal keratitis), uveitis, glaucoma; emergent ophthalmology (AAO HZO PPP)

12-phase flow (12)

  1. 1FRAME
    VZV disease spectrum: primary varicella (chickenpox) + herpes zoster (shingles) + PHN + complications (disseminated, HZO, Ramsay Hunt, pneumonitis, encephalitis, vasculopathy, hepatitis, IRIS) + vaccine eligibility (RZV ≥ 50 routine; ≥ 19 immunocompromised; varicella vaccine 2-dose childhood + susceptible adult catch-up) (Gershon Nat Rev Dis Primers 2015; Dooling MMWR 2018)
    inputs: age, rash_onset_time
    advance: VZV phenotype framed (primary varicella vs zoster vs PHN vs complication vs vaccination eligibility)
  2. 2ENTRY
    Recognise via clinical features: vesicular rash (generalised crops vs dermatomal); Hutchinson sign (HZO); ear vesicles + facial palsy (Ramsay Hunt); persistent neuropathic pain (PHN); high-risk exposure (VariZIG); maternal varicella near delivery; vaccination-eligible age threshold
    inputs: rash_distribution_and_pattern, pain_assessment_neuropathic_features
    advance: Phenotype hypothesis (primary varicella / zoster / complication / PHN / vaccination-eligible) framed
  3. 3CONTEXT
    Age + vaccination history (varicella + RZV / Zostavax) + prior varicella / zoster + immunocompromise status (HIV CD4, transplant, chemo nadir, chronic steroid, autoimmune biologic) + pregnancy gestational age + maternal varicella exposure timing; community / household exposure context; serology if vaccination decision needs immunity stratification
    inputs: vaccination_history_varicella_and_rzv, prior_varicella_or_zoster_history, pregnancy_status_and_gestational_age, immunocompromise_status
    advance: Host + exposure context captured
  4. 4RED_FLAGS
    Life-threatening features: severe pneumonitis (SpO2 < 94%), encephalitis / vasculopathy (focal neuro deficits, seizures, encephalopathy), Hutchinson sign with corneal-involvement risk, Ramsay Hunt with facial palsy, neonatal varicella from maternal disease 5 d pre to 2 d post delivery, disseminated zoster in immunocompromised — empiric IV acyclovir within 1 h + ICU / NICU / ID + emergent ophthalmology if HZO
    inputs: oxygen_saturation, cranial_nerve_or_neuro_features, temperature_and_systemic_symptoms
    actions: flag:emergent_iv_acyclovir_if_severe (Gilden CID 2021; AAP Red Book 2024), flag:emergent_ophthalmology_if_hutchinson_sign (AAO HZO PPP), flag:varizig_within_96h_if_high_risk_susceptible_exposed (CDC; AAP Red Book 2024), flag:nicu_admission_neonatal_varicella (AAP Red Book 2024)
    advance: Red flags actioned; emergent consults + empirics in place
  5. 5INITIAL_WORKUP
    Clinical diagnosis is primary for both varicella and zoster (rash + distribution); PCR reserved for atypical / immunocompromised / vasculopathy. For severe / immunocompromised / vasculopathy: VZV PCR (vesicle swab, CSF, blood), CSF cell count + protein + glucose if neuro, LFT for hepatitis suspicion, CXR if respiratory, creatinine baseline. VZV IgG serology for immunity testing (vaccination decisions, pregnant susceptibility, post-exposure prophylaxis stratification). Initiate antiviral on clinical recognition — do NOT wait for PCR (Cohen NEJM 2013; Gershon Nat Rev Dis Primers 2015)
    inputs: creatinine_and_renal_function
    actions: panel.cbc, panel.lft, panel.renal
    advance: Diagnosis confirmed clinically; PCR sent if atypical or severe; baseline labs drawn; antiviral initiated
  6. 6BRANCHING_WORKUP
    Site-directed: slit-lamp + fluorescein + IOP for HZO; audiology + ENT consult for Ramsay Hunt; MRI brain for VZV encephalitis / vasculopathy (temporal lobe + insular + multifocal infarcts); CXR for pneumonitis; coagulation panel if disseminated; LP + CSF VZV PCR + intrathecal antibody index for neuro disease (especially vasculopathy); echocardiography if disseminated with shock (rare HZV myocarditis); BMP + glucose if dehydration
    inputs: chest_xray_if_respiratory, mri_brain_if_neuro_features, slit_lamp_eye_exam_if_hzo, lft_for_hepatitis_assessment, vzv_pcr_vesicle_swab_or_csf_or_blood
    advance: Site-specific complications evaluated; sub-specialty consults engaged
  7. 7DIFFERENTIAL
    Primary varicella vs HFMD (coxsackievirus — palms + soles), drug eruption (DRESS, SJS), bullous impetigo, eczema herpeticum (HSV in atopic), HFMD vs varicella in young child. Zoster vs HSV (recurrent labialis / genitalis non-dermatomal), contact dermatitis, bullous insect bite, dermatomal nerve compression with rash. Ramsay Hunt vs Bell palsy idiopathic. HZO vs orbital cellulitis, periorbital cellulitis, contact dermatitis. PHN vs other neuropathic pain (diabetic neuropathy, trigeminal neuralgia). VZV encephalitis vs HSV encephalitis (HSV more common; empiric IV acyclovir covers both pending PCR) (Gershon Nat Rev Dis Primers 2015; Cohen NEJM 2013)
    inputs: vzv_serology_igg_for_immunity
    advance: Look-alikes evaluated; PCR or DFA if diagnostic uncertainty in immunocompromised / atypical
  8. 8RISK_STRATIFICATION
    Stratify by phenotype + host: (1) primary varicella immunocompetent pediatric = mild outpatient supportive only; (2) primary varicella adult / immunocompromised / pregnant = oral antiviral (PO) or IV acyclovir if severe; (3) uncomplicated zoster immunocompetent ≥ 50 = oral antiviral within 72 h; (4) HZO with Hutchinson sign = emergent ophthalmology + oral / IV antiviral + topical; (5) Ramsay Hunt = oral antivirals + steroids + neuro + ENT; (6) disseminated / pneumonitis / encephalitis / vasculopathy / neonatal = IV acyclovir + ICU + ID; (7) PHN = neuropathic pain ladder + pain medicine; (8) vaccination-eligible = RZV 2-dose schedule
    inputs: immunocompromise_status, pregnancy_status_and_gestational_age
    advance: Severity tier + setting assigned
  9. 9TREATMENT
    Antiviral per phenotype: (a) primary varicella in adult ≥ 13 yo + within 24 h = acyclovir 800 mg PO 5×/d × 5-7 d (OR valacyclovir 1 g PO TID × 5-7 d); pediatric immunocompetent < 12 yo = supportive only, NO routine antiviral; (b) zoster uncomplicated ≥ 50 immunocompetent + within 72 h = valacyclovir 1 g PO TID × 7 d (preferred) OR famciclovir 500 mg PO TID × 7 d OR acyclovir 800 mg PO 5×/d × 7 d; (c) severe / disseminated / pneumonitis / encephalitis / vasculopathy / immunocompromised / pregnant pneumonitis / neonatal varicella = IV acyclovir 10-15 mg/kg q8h × 7-14 d (q12h if preterm neonate); (d) HZO = oral valacyclovir 1 g PO TID × 7-10 d + topical antiviral (trifluridine or ganciclovir gel) + ophthalmology direction; (e) Ramsay Hunt = oral valacyclovir 1 g TID × 7-10 d + prednisone 60 mg/d × 5 d then taper; (f) VariZIG 125 IU per 10 kg (max 625 IU) IM within 96 h (CDC expanded to 10 d) for high-risk susceptible exposed (immunocompromised, pregnant, neonatal). Foscarnet 40 mg/kg q8h IV rescue for documented acyclovir resistance (rare). PHN ladder: gabapentin 300 mg HS titrated to 900-3600 mg/d divided TID OR pregabalin 75 mg BID titrated to 150-300 mg/d OR nortriptyline 25 mg HS titrated to 75-150 mg HS OR topical lidocaine 5% patch 12 h on / 12 h off OR topical capsaicin 8% patch (Qutenza in-office) OR opioids if severe / refractory + pain medicine referral. Supportive: acetaminophen for fever / pain; AVOID aspirin (Reye in varicella); AVOID ibuprofen (emerging necrotising fasciitis signal in varicella per AAP). RZV (Shingrix) 2-dose 2-6 mo apart for ≥ 50 routine and ≥ 19 immunocompromised (separate from acute disease treatment).
    inputs: rash_onset_time, age, creatinine_and_renal_function
    advance: Antiviral + analgesia + supportive + sub-specialty consults + VariZIG (if exposed) ordered; RZV vaccination plan if eligible
  10. 10DISPOSITION
    Outpatient: uncomplicated zoster on oral antivirals; primary varicella in immunocompetent child; PHN management; post-exposure prophylaxis. Inpatient: severe immunocompromised zoster on IV acyclovir × 7-14 d; severe primary varicella adult with complications not requiring ICU; HZO observation 24-48 h with ophthalmology co-management; pregnancy with severe disease without ICU need. ICU: disseminated / pneumonitis / encephalitis / vasculopathy / refractory shock / pregnant pneumonitis requiring ventilator; neonatal varicella NICU. Transfer to specialty centre if VZV vasculopathy + stroke pattern (neurology + ID).
    inputs: oxygen_saturation
    advance: Setting + duration of care assigned
  11. 11MONITORING
    Outpatient zoster: rash resolution expected 1-2 wk; new lesions cease forming 3-5 d on antivirals; return precautions for new neuro / ophthalmic / disseminated features. Inpatient / ICU: serial creatinine + UOP for acyclovir crystalline nephropathy; LFT trend if hepatitis; daily reassessment of antiviral duration; CSF VZV PCR follow-up if vasculopathy (some centres at d 14). PHN: pain scale (NRS) at every visit; dose-titrate gabapentinoid or TCA; pain medicine referral if refractory. Vaccination tracking: dose 2 of RZV at 2-6 mo after dose 1 (do NOT restart if > 6 mo — give dose 2 ASAP).
    inputs: creatinine_and_renal_function, lft_for_hepatitis_assessment
    actions: panel.renal, panel.lft
    advance: Response confirmed; antiviral course completion + PHN ladder + RZV second dose scheduled
  12. 12FOLLOWUP
    Post-zoster: PHN surveillance at 1 mo, 3 mo (PHN diagnostic threshold), 6 mo; pain medicine + neurology if refractory. Post-HZO: ophthalmology lifetime follow-up for keratitis / uveitis / glaucoma recurrence. Post-Ramsay Hunt: facial recovery tracking (~ 40% complete recovery vs ~ 70% for Bell palsy) + audiology + ENT. Post-vasculopathy: stroke prevention + cerebrovascular follow-up. Vaccination reconciliation: RZV 2-dose ≥ 50 routine / ≥ 19 immunocompromised; varicella vaccine 2-dose susceptible adult catch-up; pediatric 2-dose schedule audit (12-15 mo + 4-6 yr). Family education + contact tracing if institutional outbreak; report to public health if needed.
    advance: Follow-up + vaccination plan + PHN ladder set; education delivered