Influenza: Symptoms, Treatment, and Recovery
Typical Symptoms
Influenza presents with abrupt onset of fever (>38°C), cough, chills or sweats, myalgias, and malaise 1. The hallmark is the sudden nature of symptom onset, distinguishing it from other respiratory infections 2, 3.
Key clinical features include:
- Fever (>38°C) - though immunocompromised and very elderly patients may not mount adequate febrile response
- Respiratory symptoms: nonproductive cough, sore throat
- Systemic symptoms: myalgias, headache, malaise, chills
- Duration: Clinical symptoms typically last 6-8 days in otherwise healthy adults 4
Important caveat: Lassitude, cough, and small-airways disease may persist for weeks even after acute symptoms resolve 3. In young children, laryngotracheobronchitis, pneumonia, and unexplained fever are prominent manifestations requiring hospitalization 3.
Treatment Approach
Antiviral Therapy
For patients presenting within 48 hours of symptom onset with fever >38°C and acute influenza-like illness, oseltamivir 75 mg every 12 hours for 5 days should be initiated 5. This represents the most established treatment based on guideline evidence.
Treatment algorithm by severity:
Non-severe influenza:
- High-risk patients (elderly, immunocompromised, pregnant, chronic medical conditions): Start oseltamivir or baloxavir within 48 hours 6, 7
- Previously healthy adults: Antivirals can be considered if initiated within 48 hours, though benefit is primarily reducing illness duration by approximately 24 hours 1
- Dose adjustment: Reduce oseltamivir to 75 mg once daily if creatinine clearance <30 ml/min 5
Severe influenza (hospitalized patients):
- Start oseltamivir immediately, even if >48 hours from symptom onset, particularly in immunocompromised patients 5, 8
- Evidence from observational studies suggests therapeutic benefit beyond 48 hours in hospitalized and high-risk patients 8
Antibiotic Use
Previously well adults with uncomplicated influenza do NOT routinely require antibiotics 5. This is a critical point to avoid inappropriate antibiotic use.
Antibiotics should be considered when:
- Worsening symptoms develop (recrudescent fever or increasing dyspnea) 5
- Influenza-related pneumonia is present
- High-risk patients develop lower respiratory features
For non-severe pneumonia: Co-amoxiclav or tetracycline orally 5
Alternative regimens: Macrolides (clarithromycin/erythromycin) or fluoroquinolones active against S. pneumoniae and S. aureus for penicillin-intolerant patients 5
Adjunctive Therapies
Strong recommendation AGAINST:
- Corticosteroids in severe influenza - associated with increased mortality and bacterial superinfection 8, 6
- Antibiotics in non-severe uncomplicated influenza 6
- Macrolides, mTOR inhibitors, NSAIDs, passive immune therapy as adjunctive treatments 6
Supportive care includes:
- Assessment for volume depletion and cardiac complications 5
- Nutritional support in severe or prolonged illness 5
- Monitoring vital signs at least twice daily (temperature, respiratory rate, pulse, blood pressure, mental status, oxygen saturation) 5
Recovery Timeline
Expect 6-8 days of clinical symptoms with 4-5 days of sick leave in otherwise healthy adults 4.
Convalescence recommendations:
- Standard cases: 7 days from symptom onset 4
- Mild cases with brief symptoms: Minimum 4 days convalescence 4
- Shorter durations are NOT recommended due to transmission risk
Transmission considerations: Viral spread occurs primarily during the initial 4 days of illness 4. Patients remain contagious during this period and should avoid contact with high-risk individuals.
Hospital Discharge Criteria
Patients should be reviewed 24 hours before discharge. Keep hospitalized if ≥2 of the following are present 5:
- Temperature >37.8°C
- Heart rate >100/min
- Respiratory rate >24/min
- Systolic blood pressure <90 mmHg
- Oxygen saturation <90%
Follow-up: Clinical review should be arranged for all patients with significant complications or worsening of underlying disease 5.
Key Clinical Pitfalls
- Don't wait for laboratory confirmation in outpatient settings - diagnosis is clinical 1
- Don't withhold antivirals in severely ill hospitalized patients even if >48 hours from symptom onset 5, 8
- Don't prescribe antibiotics reflexively - only when bacterial superinfection is suspected 5, 6
- Don't use corticosteroids in severe influenza despite their use in other respiratory conditions 8, 6
- Don't underestimate recovery time - patients may have persistent symptoms for weeks despite acute illness resolution 3