What is the recommended treatment and management after flu exposure to symptom onset?

Management After Flu Exposure to Symptom Onset

For patients who develop influenza-like illness after known flu exposure, initiate oseltamivir 75 mg twice daily for 5 days if they present within 48 hours of symptom onset, have fever >38°C, and meet criteria for acute influenza-like illness. 1, 2

Immediate Assessment Upon Symptom Development

When symptoms appear after flu exposure, evaluate for three critical criteria that determine antiviral eligibility 1, 3:

• Acute influenza-like illness (cough, fever/feverishness, plus headache, myalgia, or sore throat) 3
• Fever >38°C (documented temperature) 1
• Symptomatic for ≤48 hours (treatment window) 1, 2

Common pitfall: Patients unable to mount adequate febrile response (immunocompromised, very elderly) may still qualify for antiviral treatment despite lack of documented fever. 1

Antiviral Treatment Algorithm

Standard Patients (Immunocompetent)

If all three criteria above are met:

• Oseltamivir 75 mg orally twice daily for 5 days 1, 2
• Adjust to 75 mg once daily if creatinine clearance <30 mL/min 1, 2
• Greatest benefit occurs when started within 24 hours of symptom onset 4

High-Risk or Severely Ill Patients

Consider treatment even beyond 48 hours for: 1, 3

• Hospitalized patients with severe illness 1
• Immunocompromised patients 1
• Patients with significant comorbidities (asthma, COPD, cardiac disease) 5

Critical consideration: Hospitalized and severely ill patients may benefit from oseltamivir even when started >48 hours after symptom onset, particularly if immunocompromised, though evidence for benefit beyond this window is limited. 1, 3

Post-Exposure Prophylaxis vs. Early Treatment

Key distinction: If the patient is still asymptomatic after exposure, prophylaxis dosing differs from treatment 1, 2:

• Prophylaxis (asymptomatic): Oseltamivir 75 mg once daily for 10 days following close contact 1, 2
• Treatment (symptomatic): Oseltamivir 75 mg twice daily for 5 days 1, 2

For solid organ transplant recipients or recent transplant patients: Counsel to watch for early symptoms and provide prescription with treatment doses to initiate immediately when symptoms develop. 1

Antibiotic Management: When to Add

Do NOT routinely prescribe antibiotics for uncomplicated influenza. 1, 3

Add antibiotics only if: 1, 3

• Worsening symptoms after initial improvement (recrudescent fever, increasing dyspnea) 1
• High-risk patients develop lower respiratory tract features 1
• Clinical or radiographic evidence of bacterial pneumonia 1, 3

Antibiotic Selection When Indicated

For non-severe influenza-related pneumonia: 1, 3

• First-line oral: Co-amoxiclav or tetracycline 1, 3
• Alternative: Macrolide (clarithromycin) or respiratory fluoroquinolone (levofloxacin, moxifloxacin) 1

For severe influenza-related pneumonia requiring hospitalization: 1, 3

• IV co-amoxiclav or 2nd/3rd generation cephalosporin (cefuroxime, cefotaxime) PLUS macrolide (clarithromycin or erythromycin) 1, 3
• Administer within 4 hours of admission 1

Critical pitfall: Staphylococcus aureus (including MRSA) is an important cause of secondary bacterial pneumonia during influenza season with high mortality; ensure empiric coverage addresses this pathogen in severe cases. 6

Monitoring for Complications

Reassess urgently if: 7

• No improvement after 3-5 days of illness 7
• Deterioration after initial improvement 7
• New or worsening dyspnea, productive cough, chest pain 7
• Oxygen saturation <92% 7
• Persistent fever beyond 5 days 7

These indicators suggest pneumonia development or bacterial coinfection requiring chest radiograph and possible antibiotic therapy. 7

Special Populations

Immunocompromised Patients

• May require extended antiviral therapy if viral replication persists beyond 7-10 days 1
• Consider antiviral resistance testing if symptoms persist despite treatment 1
• Prophylaxis may be extended up to 12 weeks during community outbreaks 1, 2

Patients with Asthma or COPD

• Never prescribe zanamivir (inhaled neuraminidase inhibitor) due to risk of fatal bronchospasm 5
• Oseltamivir is the only appropriate neuraminidase inhibitor for patients with underlying airways disease 5

Supportive Care Measures

All patients should receive: 3

• Antipyretics for fever control (avoid aspirin in children due to Reye's syndrome risk) 3
• Adequate hydration 1
• Nutritional support in severe or prolonged illness 1

Critical Red Flags Requiring Immediate Hospitalization

Transfer to hospital immediately if: 7

• Oxygen saturation <92% on room air 7
• Respiratory rate ≥30 breaths/min 7
• Systolic blood pressure <90 mmHg 7
• Confusion or altered mental status 7
• Evidence of septic shock or organ dysfunction 7