Patient handout

Influenza (acute)

PRODUCTION

1. Your condition

This handout is for influenza (acute). Your care team identified this based on: influenza-like illness: acute onset fever ≥100f + cough or sore throat during influenza season (idsa 2018; cdc 2024).

Other reasons your team may use this plan: 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); hospitalized patient with suspected or confirmed influenza — empiric oseltamivir pending testing (idsa 2018).

2. Your medications

Take these medications exactly as prescribed. Do not stop or change a dose without talking to your provider.

Medication	Starting dose	How	When	What it does
oseltamivir	75 mg	PO	BID × 5 days	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)
baloxavir marboxil	40 mg (<80 kg) or 80 mg (≥80 kg)	PO	single dose	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)
peramivir	600 mg	IV	single dose	IV alternative when oral/enteral not feasible; single 600mg dose non-inferior to 5d oseltamivir for uncomplicated influenza (IDSA 2018; CDC 2024)

Plan: Antiviral therapy — uncomplicated outpatient influenza ≤48h (IDSA 2018; CDC 2024)

3. When to call your provider

Contact your care team if any of the following happen:

oxygen level (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)

4. When to seek emergency care

Call 911 or go to the nearest emergency room right away if you have:

Influenza pneumonia with ARDS (PaO2/FiO2 ≤300), bilateral infiltrates, requiring supplemental oxygen or mechanical ventilation (IDSA 2018; WHO 2024)(life-threatening)
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)
Pregnant patient with confirmed/suspected influenza at any gestational age — increased risk of hospitalization, ICU admission, and death (IDSA 2018; CDC 2024)
Immunocompromised patient with influenza — risk of prolonged viral shedding, antiviral resistance emergence, progressive viral pneumonia (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)
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)
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)(life-threatening)
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)
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)

5. Follow-up

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)

6. Sources

Guideline: IDSA 2018 Clinical Practice Guidelines for Seasonal Influenza (Uyeki Clin Infect Dis 2019) + CDC 2024 antiviral guidance + WHO 2024