Symptoms and Treatment of Influenza
Influenza is characterized by the sudden onset of constitutional and respiratory symptoms including fever, myalgia, headache, malaise, nonproductive cough, sore throat, and rhinitis, typically with fever. 1 These classic symptoms develop abruptly and can cause significant morbidity and mortality if not properly managed.
Clinical Presentation of Influenza
Core Symptoms
- Fever: Often high (>38°C/100°F), sudden onset
- Respiratory symptoms:
- Nonproductive cough
- Sore throat
- Runny nose (rhinitis)
- Systemic symptoms:
- Myalgia (muscle aches)
- Headache
- Malaise/fatigue
- Chills/sweats
The typical incubation period for influenza is 1-4 days (average: 2 days) 1, and uncomplicated influenza typically resolves after 3-7 days, although cough and malaise can persist for more than 2 weeks 2.
Symptom Severity by Patient Group
- Children: May present with higher fevers, more prominent gastrointestinal symptoms including nausea and vomiting 1
- Elderly: May present with less pronounced fever but more severe complications
- Immunocompromised: May have prolonged viral shedding for weeks or months 2
Diagnosis
Diagnosis is primarily clinical, based on symptoms and knowledge of local influenza prevalence 1. Laboratory confirmation is not necessary for most outpatient cases but may be useful in:
- Hospitalized patients
- Patients where diagnosis will change treatment decisions
- During early influenza season to confirm circulation
Rapid molecular assays are the preferred diagnostic tests when testing is indicated 3.
Treatment Options
Antiviral Medications
Neuraminidase inhibitors should be started within 48 hours of symptom onset, preferably within 24 hours for maximum benefit. 1, 4
Oseltamivir (Tamiflu):
- Adults: 75 mg twice daily for 5 days
- Reduces duration of illness by approximately 1-1.3 days 4
- Dosage adjustment needed for renal impairment (CrCl <30 ml/min)
Zanamivir:
- Alternative option when oseltamivir is not appropriate
- Most effective when started within 30 hours of symptom onset 1
Treatment priority groups:
- High-risk patients (pregnant women, elderly, chronic medical conditions)
- Patients with severe or progressive illness
- Immunocompromised individuals
Symptomatic Treatment
For uncomplicated influenza, symptomatic treatment includes:
- Antipyretics/analgesics (acetaminophen or ibuprofen) for fever and pain
- Rest and adequate hydration
- Avoiding smoking
- Topical decongestants, throat lozenges, or saline nasal drops may provide relief 1
Management of Complications
Respiratory Complications
- Secondary bacterial pneumonia: Requires antibiotic therapy
- Oral co-amoxiclav or tetracycline for non-severe cases
- IV antibiotics for severe cases 1
Special Considerations
- Severe influenza: Characterized by persistent high fever >3 days, severe cough, dyspnea, altered mental status, or dehydration 1
- Immunocompromised patients: May require longer treatment courses and closer monitoring
Prevention
Annual influenza vaccination is the most effective preventive strategy 5. For high-risk individuals exposed to influenza:
- Chemoprophylaxis with oseltamivir or zanamivir can be considered 1
- Standard and droplet precautions for hospitalized patients 2
When to Seek Medical Care
Patients should seek medical attention if they experience:
- Persistent high fever beyond 3 days
- Difficulty breathing or shortness of breath
- Pain or pressure in the chest
- Sudden dizziness or confusion
- Severe or persistent vomiting
- Symptoms that improve but then return with worse fever/cough
Return to Normal Activities
Individuals should not return to work or school until:
- Fever has resolved for at least 24 hours without fever-reducing medications
- Most acute symptoms have improved
- They can perform normal activities without excessive fatigue 2
Early recognition of symptoms and prompt initiation of appropriate treatment are crucial for reducing the duration and severity of influenza illness and preventing complications.