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id.influenza.core.v1PRODUCTION
id.influenza.core.v1

Influenza (acute)

infectious_diseaseacuteadult
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12/12 authored

Canonical 12-phase frame with authored status for this dossier.

Current phase

Frame

Detailed

Confirm acute influenza context: ILI during influenza season, symptom onset time documented — scope includes diagnosis, antiviral treatment, and complication management; excludes avian influenza (H5N1) and pandemic strains requiring separate protocols (IDSA 2018; CDC 2024)

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Influenza suspected and onset timing established

Patient inputs (13)

Age ≥65 is high-risk for complications; age determines antiviral dosing (IDSA 2018; CDC 2024)

Antiviral benefit greatest ≤48h of symptom onset; oseltamivir and baloxavir most effective if started early (IDSA 2018; Hayden NEJM 2018; Dobson Lancet 2015)

Rapid molecular assay preferred (sensitivity 95-99%); RIDT sensitivity only 50-70% — negative RIDT does not exclude influenza (IDSA 2018; CDC 2024)

Pregnancy is high-risk for severe influenza; oseltamivir preferred antiviral; baloxavir contraindicated in pregnancy — insufficient data (IDSA 2018; CDC 2024)

Immunocompromised patients may have prolonged viral shedding; consider extended oseltamivir course and ID consultation (IDSA 2018; CDC 2024)

Mild outpatient vs severe/progressive (dyspnea, persistent fever, hemodynamic instability) determines setting (IDSA 2018)

Pregnancy, immunocompromised, age ≥65, chronic cardiopulmonary/renal/hepatic/metabolic disease, morbid obesity BMI ≥40, nursing home residents — all warrant empiric antiviral regardless of testing (IDSA 2018; CDC 2024)

SpO2 <94% on room air = severe influenza warranting hospitalization (IDSA 2018; WHO 2024)

CXR if hypoxia, dyspnea, or suspected pneumonia — bilateral infiltrates suggest primary viral pneumonia vs focal consolidation for bacterial superinfection (IDSA 2018)

Procalcitonin helps distinguish primary viral pneumonia (low) from bacterial superinfection (elevated >0.25) — guides antibiotic decision (IDSA 2018)

Prior influenza vaccination does not exclude diagnosis; vaccinated patients may have milder disease (IDSA 2018; CDC 2024)

Leukopenia, lymphopenia, thrombocytopenia common in severe influenza; leukocytosis suggests bacterial superinfection (IDSA 2018)

Renal function for oseltamivir dose adjustment (CrCl <30: 75mg daily); hepatic function (IDSA 2018)

* = hard-required. Engine cannot meaningfully run until these are filled.

Severity triggers (9)

9 need judgement
  • informationallife_threateningcritical_influenza_pneumonia — IDSA 2018
    Influenza pneumonia with ARDS (PaO2/FiO2 ≤300), bilateral infiltrates, requiring supplemental oxygen or mechanical ventilation (IDSA 2018; WHO 2024)
    Trigger could not be auto-evaluated — needs clinician judgement.
  • informationallife_threateningards_progression — IDSA 2018
    Influenza pneumonia + bilateral infiltrates + PaO2/FiO2 < 200 (moderate ARDS per Berlin definition) — ICU transfer + ARDSnet lung-protective ventilation (Vt 4-8 mL/kg PBW, plateau pressure ≤ 30 cm H2O, driving pressure ≤ 15) + prone positioning if PaO2/FiO2 < 150 (PROSEVA Guérin NEJM 2013) + VV-ECMO consideration if refractory hypoxemia in young patient; routes to pulm.ards.core.v1 (IDSA 2018; WHO 2024)
    Trigger could not be auto-evaluated — needs clinician judgement.
  • informationalseverebacterial_superinfection — IDSA 2018
    Secondary bacterial pneumonia — biphasic illness with recurrent fever, focal consolidation, leukocytosis, elevated procalcitonin; S. aureus (including MRSA), S. pneumoniae, S. pyogenes most common (IDSA 2018)
    Trigger could not be auto-evaluated — needs clinician judgement.
  • informationalsevereinfluenza_in_pregnancy — IDSA 2018
    Pregnant patient with confirmed/suspected influenza at any gestational age — increased risk of hospitalization, ICU admission, and death (IDSA 2018; CDC 2024)
    Trigger could not be auto-evaluated — needs clinician judgement.
  • informationalsevereimmunocompromised_prolonged_shedding — IDSA 2018
    Immunocompromised patient with influenza — risk of prolonged viral shedding, antiviral resistance emergence, progressive viral pneumonia (IDSA 2018)
    Trigger could not be auto-evaluated — needs clinician judgement.
  • informationalseverehigh_risk_outpatient_without_antiviral — IDSA 2018
    High-risk outpatient with ILI not yet on antiviral therapy: pregnancy / age ≥ 65 / chronic cardiopulm/renal/hepatic/metabolic disease / immunocompromise / morbid obesity BMI ≥ 40 / nursing-home resident / age < 2 years — start oseltamivir immediately even if symptom onset > 48 h (IDSA 2018; CDC ACIP 2025-2026)
    Trigger could not be auto-evaluated — needs clinician judgement.
  • informationalseverebacterial_superinfection_features — IDSA 2018
    Biphasic illness pattern (initial improvement → recurrent fever) + new productive cough + new focal infiltrate on CXR + leukocytosis OR procalcitonin > 0.25 ng/mL — add empiric anti-MRSA + anti-pseudomonal coverage; route bacterial component to pulm.cap.core.v1 or id.sepsis.core.v1 for shock; S. aureus including MRSA + S. pneumoniae + S. pyogenes most common (IDSA 2018)
    Trigger could not be auto-evaluated — needs clinician judgement.
  • informationalsevereinfluenza_encephalitis_features — IDSA 2018
    Altered mental status + fever in confirmed/suspected influenza + viral-pattern CSF (lymphocytic pleocytosis, normal-to-mildly-elevated protein, normal glucose, negative bacterial culture and Gram-stain) — neurology consult + empiric IV acyclovir 10 mg/kg q8h until HSV PCR result + continue oseltamivir + MRI brain for influenza-associated necrotizing encephalopathy pattern + EEG if seizures (IDSA 2018)
    Trigger could not be auto-evaluated — needs clinician judgement.
  • informationalsevereinfluenza_myocarditis_features — IDSA 2018
    Chest pain + new ECG changes (ST changes, new conduction block) + elevated troponin in setting of confirmed/suspected influenza ± new HF features (EF drop on echo, regional wall-motion abnormalities, new pulmonary edema) — echocardiography + cardiology consult + telemetry + standard HF therapy (guideline-directed but cautious diuresis to avoid hypotension) + continue oseltamivir + consider CMR if available (IDSA 2018)
    Trigger could not be auto-evaluated — needs clinician judgement.

Workflow calculators

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RISK_STRATIFICATIONoptionalDrives risk stratification
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Recommended regimen

Antiviral therapy — uncomplicated outpatient influenza ≤48h (IDSA 2018; CDC 2024)
axis: antiviral_uncomplicated_outpatient
Selected axis "Antiviral therapy — uncomplicated outpatient influenza ≤48h (IDSA 2018; CDC 2024)" by default fallback (first axis)
  • oseltamivir
    first line
    neuraminidase_inhibitor
    75 mg • PO • BID × 5 days
    triggers: ili_any_severity_high_risk, ili_le_48h_any_patient, hospitalized_empiric
    First-line antiviral for all patients warranting treatment; IPD meta-analysis: 25% reduction in time to first alleviation of symptoms in adults (Dobson Lancet 2015); 1-day median reduction symptom duration; reduces hospitalization in high-risk (IDSA 2018; CDC 2024)
    rxcui 260101
  • baloxavir marboxil
    first line
    cap_dependent_endonuclease_inhibitor
    40 mg (<80 kg) or 80 mg (≥80 kg) • PO • single dose
    triggers: uncomplicated_le_48h_age_ge_12, high_risk_outpatient_le_48h
    Single-dose convenience; CAPSTONE-1: median time to symptom improvement 26.5h faster vs placebo, viral load reduction significantly greater than oseltamivir (Hayden NEJM 2018); FDA-approved for high-risk patients (IDSA 2018; CDC 2024)
    rxcui 2099995
  • peramivir
    second line
    neuraminidase_inhibitor
    600 mg • IV • single dose
    triggers: unable_to_tolerate_oral_or_enteral
    IV alternative when oral/enteral not feasible; single 600mg dose non-inferior to 5d oseltamivir for uncomplicated influenza (IDSA 2018; CDC 2024)
    rxcui 619693

outpatient playbook — drug actions (3)

  1. 1. oseltamivir 75 mg BID × 5d
    75 mg • PO • BID
    trigger: High-risk patient with ILI regardless of symptom duration or test result (IDSA 2018)
    First-line antiviral; 25% symptom duration reduction (Dobson Lancet 2015); reduces hospitalization in high-risk (IDSA 2018)
  2. 2. baloxavir 40-80 mg single dose
    40-80 mg weight-based • PO • single dose
    trigger: Uncomplicated influenza ≤48h, age ≥12, alternative to oseltamivir (Hayden NEJM 2018)
    Single-dose convenience; superior viral load reduction vs oseltamivir (CAPSTONE-1 — Hayden NEJM 2018)
  3. 3. acetaminophen 500-1000 mg q6h PRN
    500-1000 mg • PO • q6h PRN
    trigger: Fever, myalgia, headache (IDSA 2018)
    Symptomatic relief; preferred over NSAIDs in pregnancy (IDSA 2018)

Auto-drafted A&P note

outpatient

Subjective

- Possible entry pathways: Influenza-like illness: acute onset fever ≥100F + cough or sore throat during influenza season (IDSA 2018; CDC 2024); Positive rapid influenza diagnostic test (RIDT), rapid molecular assay, or RT-PCR (IDSA 2018); Close contact with confirmed influenza case in high-risk individual — post-exposure prophylaxis consideration (IDSA 2018; CDC 2024).

Objective

- No vitals, labs, or imaging entered for this encounter.

Assessment

**Influenza (acute)** (id.influenza.core.v1).
Phenotype framing: Distinguish influenza from: COVID-19 (co-testing recommended — IDSA 2018; CDC 2024), RSV (older adults, immunocompromised), bacterial pneumonia, other viral URI, early sepsis — multiplex respiratory panels discriminate (IDSA 2018)
Scope: Confirm acute influenza context: ILI during influenza season, symptom onset time documented — scope includes diagnosis, antiviral treatment, and complication management; excludes avian influenza (H5N1) and pandemic strains requiring separate protocols (IDSA 2018; CDC 2024)

No severity triggers fired against current inputs.

Plan

Regimen axis: **Antiviral therapy — uncomplicated outpatient influenza ≤48h (IDSA 2018; CDC 2024)**.
1. oseltamivir 75 mg PO BID × 5 days (neuraminidase_inhibitor, first line) — First-line antiviral for all patients warranting treatment; IPD meta-analysis: 25% reduction in time to first alleviation of symptoms in adults (Dobson Lancet 2015); 1-day median reduction symptom duration; reduces hospitalization in high-risk (IDSA 2018; CDC 2024)
2. baloxavir marboxil 40 mg (<80 kg) or 80 mg (≥80 kg) PO single dose (cap_dependent_endonuclease_inhibitor, first line) — Single-dose convenience; CAPSTONE-1: median time to symptom improvement 26.5h faster vs placebo, viral load reduction significantly greater than oseltamivir (Hayden NEJM 2018); FDA-approved for high-risk patients (IDSA 2018; CDC 2024)
3. peramivir 600 mg IV single dose (neuraminidase_inhibitor, second line) — IV alternative when oral/enteral not feasible; single 600mg dose non-inferior to 5d oseltamivir for uncomplicated influenza (IDSA 2018; CDC 2024)

Setting playbook (outpatient) — Diagnose influenza, risk-stratify, initiate antiviral within 48h for eligible patients, and provide return precautions (IDSA 2018; CDC 2024)
4. oseltamivir 75 mg BID × 5d 75 mg PO BID — High-risk patient with ILI regardless of symptom duration or test result (IDSA 2018) (First-line antiviral; 25% symptom duration reduction (Dobson Lancet 2015); reduces hospitalization in high-risk (IDSA 2018))
5. baloxavir 40-80 mg single dose 40-80 mg weight-based PO single dose — Uncomplicated influenza ≤48h, age ≥12, alternative to oseltamivir (Hayden NEJM 2018) (Single-dose convenience; superior viral load reduction vs oseltamivir (CAPSTONE-1 — Hayden NEJM 2018))
6. acetaminophen 500-1000 mg q6h PRN 500-1000 mg PO q6h PRN — Fever, myalgia, headache (IDSA 2018) (Symptomatic relief; preferred over NSAIDs in pregnancy (IDSA 2018))

Non-pharmacologic actions:
- Rapid molecular influenza testing (IDSA 2018)
- COVID-19 co-testing during respiratory illness season (CDC ACIP 2025-2026)
- Isolation until afebrile ≥24h without antipyretics (CDC ACIP 2025-2026)
- Hand hygiene and respiratory etiquette education (CDC ACIP 2025-2026)
- Return precautions: worsening dyspnea, persistent fever >3d, inability to hydrate, biphasic-fever pattern (suggesting bacterial superinfection), new chest pain or troponin-suspicion features (myocarditis), altered mental status (encephalitis) (IDSA 2018)
- Post-exposure prophylaxis for high-risk household contacts: oseltamivir 75 mg PO daily × 7d OR baloxavir single dose (BLOCKSTONE Ikematsu NEJM 2020) (IDSA 2018; CDC ACIP)
- Influenza vaccination reconciliation for next season if unvaccinated — ensure ACIP-current quadrivalent (or trivalent 2024-2025+) flu vaccine + PPSV23/PCV20 pneumococcal vaccine status review per ACIP current schedule (CDC ACIP 2025-2026)
- High-risk patients (pregnancy, age ≥ 65, chronic comorbidity, immunocompromised, morbid obesity BMI ≥ 40, nursing-home resident, age < 2 years): start oseltamivir immediately even if symptom onset > 48 h per IDSA 2018 strong recommendation (do NOT wait for test result)

AVOID / contraindication checks:
- Oseltamivir_dose_reduce_to_75mg_daily_if_crcl_lt_30 (IDSA 2018)
- Baloxavir_not_recommended_pregnancy_insufficient_data (CDC 2024)
- Baloxavir_not_recommended_immunocompromised_limited_data (IDSA 2018)
- Baloxavir_avoid_with_polyvalent_cation_containing_products (Hayden NEJM 2018)
- Peramivir_dose_reduce_if_renal_impairment (IDSA 2018)

Monitoring

Regimen monitoring:
- clinical improvement expected within 48 72h of antiviral start (IDSA 2018)
- if no improvement by day 3 5 reassess diagnosis and resistance (IDSA 2018)
- do not wait for test results to start antiviral in high risk (IDSA 2018; CDC 2024)

Setting (outpatient) monitoring:
- Symptom resolution expected 3-7 days (IDSA 2018)
- Return if worsening after initial improvement — suspect bacterial superinfection (IDSA 2018)
- Phone follow-up in 48-72h for high-risk patients (IDSA 2018)

Follow-up plan: Post-influenza: ensure vaccination for next season if unvaccinated (ACIP 2025); household prophylaxis with oseltamivir 75mg daily × 7d for high-risk close contacts (IDSA 2018; CDC 2024); patient education on hand hygiene, respiratory etiquette, isolation until afebrile ≥24h (CDC 2024); report to public health if institutional outbreak (CDC 2024)
- Close-out criterion: Follow-up plan documented and prophylaxis considered

Monitoring phase: Outpatient: symptom resolution expected 3-7 days; return if worsening dyspnea, persistent high fever >3d, inability to hydrate (IDSA 2018; CDC 2024). Inpatient: daily assessment of respiratory status, SpO2, clinical improvement expected by day 3-5 of oseltamivir; if no improvement consider antiviral resistance testing, extended course, or alternative diagnosis (IDSA 2018). ICU: ventilator management per ARDS protocol, daily viral shedding assessment in immunocompromised (IDSA 2018)

Disposition

Current setting: outpatient — Diagnose influenza, risk-stratify, initiate antiviral within 48h for eligible patients, and provide return precautions (IDSA 2018; CDC 2024)

Disposition criteria:
- Discharge home if SpO2 ≥94%, adequate oral intake, reliable follow-up (IDSA 2018)
- Admit if high-risk with progressive symptoms despite antiviral (IDSA 2018)
- Refer to ED if severe symptoms, hemodynamic instability (IDSA 2018)

Escalation triggers (move to higher acuity):
- SpO2 <94% → hospitalize (IDSA 2018; WHO 2024)
- Persistent fever >3 days → reassess for bacterial superinfection (IDSA 2018)
- Dyspnea at rest or worsening → ED evaluation and CXR (IDSA 2018)
- Dehydration with inability to maintain oral intake → IV fluids, consider admission (IDSA 2018)
- Altered mental status → emergent evaluation (IDSA 2018)

Earlier-Return Triggers

Return-precaution thresholds (watch for):
- [LIFE_THREATENING] Influenza pneumonia with ARDS (PaO2/FiO2 ≤300), bilateral infiltrates, requiring supplemental oxygen or mechanical ventilation (IDSA 2018; WHO 2024)
- [LIFE_THREATENING] Influenza pneumonia + bilateral infiltrates + PaO2/FiO2 < 200 (moderate ARDS per Berlin definition) — ICU transfer + ARDSnet lung-protective ventilation (Vt 4-8 mL/kg PBW, plateau pressure ≤ 30 cm H2O, driving pressure ≤ 15) + prone positioning if PaO2/FiO2 < 150 (PROSEVA Guérin NEJM 2013) + VV-ECMO consideration if refractory hypoxemia in young patient; routes to pulm.ards.core.v1 (IDSA 2018; WHO 2024)
- [SEVERE] Secondary bacterial pneumonia — biphasic illness with recurrent fever, focal consolidation, leukocytosis, elevated procalcitonin; S. aureus (including MRSA), S. pneumoniae, S. pyogenes most common (IDSA 2018)

Citations

- IDSA 2018 Clinical Practice Guidelines for Seasonal Influenza (Uyeki Clin Infect Dis 2019) + CDC 2024 antiviral guidance + WHO 2024 [PMID:30566567](https://pubmed.ncbi.nlm.nih.gov/30566567/)
- Cited evidence (PMID 25640810) [PMID:25640810](https://pubmed.ncbi.nlm.nih.gov/25640810/)
- Cited evidence (PMID 30184455) [PMID:30184455](https://pubmed.ncbi.nlm.nih.gov/30184455/)

Last reconciled with current guidelines: 2026-05-22.
References
  • IDSA 2018 Clinical Practice Guidelines for Seasonal Influenza (Uyeki Clin Infect Dis 2019) + CDC 2024 antiviral guidance + WHO 2024 — PMID:30566567
  • Cited evidence (PMID 25640810) — PMID:25640810
  • Cited evidence (PMID 30184455) — PMID:30184455