What is the diagnosis and treatment for an adult patient with acute flu-like symptoms, including headache, earache, sore throat, yellow phlegm, and a blocked nose, who needs a medical certificate for work?

Diagnosis and Management of Acute Flu-Like Illness

Clinical Diagnosis

This patient most likely has an acute influenza-like illness (ILI), which is clinically defined as fever with new cough of acute onset in the context of community influenza circulation. 1 The presence of headache, earache, sore throat, productive cough with yellow phlegm, and nasal congestion are all consistent with this diagnosis, though the productive cough suggests possible secondary bacterial infection or acute bronchitis. 1, 2

Key Diagnostic Features Present

• Acute onset (symptoms began yesterday) with rapid worsening is characteristic of influenza 1
• Headache occurs in approximately 65% of ILI cases 1, 2
• Sore throat is present in approximately 50% of cases 1, 2
• Cough occurs in approximately 85% of ILI cases, and while typically dry, up to 40% may be productive 1
• Coryzal symptoms (blocked nose) occur in approximately 60% of cases 1, 2

Important Differential Considerations

The yellow phlegm production and earache warrant careful attention, as these may indicate:

• Acute bronchitis complicating influenza (common, especially in those with chronic conditions) 1
• Secondary bacterial infection (typically occurs 4-5 days after onset, but this patient is only at day 2) 1
• Otitis media (common complication, though more frequent in children) 1

Other respiratory pathogens can present identically to influenza, including RSV, adenovirus, rhinovirus, parainfluenza virus, Mycoplasma pneumoniae, Streptococcus pneumoniae, Chlamydia pneumoniae, and Legionella species. 1

Immediate Management Approach

Clinical Assessment Required

Assess for features suggesting complications or severe illness:

• Temperature measurement (fever typically 38-40°C in influenza) 1
• Respiratory rate (tachypnea suggests pneumonia) 3
• Oxygen saturation (SpO2 <92% requires urgent evaluation) 3
• Chest examination for crackles, wheeze, or signs of consolidation 1
• Mental status (confusion indicates severe illness) 3
• Blood pressure and heart rate (hypotension or tachycardia suggest sepsis) 3

Red Flags Requiring Immediate Hospital Referral

Any of the following mandate urgent hospital evaluation:

• Oxygen saturation <92% on room air 3
• Respiratory rate ≥30 breaths/min 3
• Systolic blood pressure <90 mmHg 3
• Confusion or altered mental status 3
• New or worsening dyspnea 3
• Inability to maintain oral intake 1

Treatment Plan

Symptomatic Management

For uncomplicated ILI without pneumonia, treatment is primarily supportive:

• Antipyretics and analgesics for fever, headache, and myalgias 4, 5
• Adequate hydration (oral fluids) 1
• Rest until symptoms resolve 5

Antiviral Therapy Consideration

Oseltamivir 75 mg twice daily for 5 days should be considered if ALL of the following criteria are met:

1. Acute influenza-like illness present 1
2. Fever >38°C documented 1
3. Symptomatic for ≤48 hours (this patient qualifies at day 2) 1, 4

The benefit is greatest when started within 24 hours of symptom onset, reducing illness duration by approximately 24 hours and potentially decreasing risk of complications. 4, 5 Since this patient is at day 2 and worsening, antiviral therapy is reasonable if influenza is circulating in the community. 1, 4

Antibiotic Therapy Decision

For this patient with productive yellow phlegm and earache:

• Previously healthy adults with acute bronchitis complicating influenza do NOT routinely require antibiotics in the absence of pneumonia 1
• However, antibiotics should be considered if the patient develops worsening symptoms (recrudescent fever or increasing dyspnea) 1
• Given the earache, examine the tympanic membranes - if otitis media is confirmed, antibiotics are indicated 1

If antibiotics are warranted, preferred oral choices include:

• Co-amoxiclav (first-line) 1
• Doxycycline (alternative) 1
• Macrolide (clarithromycin or erythromycin) if penicillin-intolerant 1

When to Initiate Antibiotics

Start antibiotics if any of the following develop:

• Clinical evidence of pneumonia on examination 1, 3
• Confirmed otitis media 1
• Failure to improve after 3-5 days 3
• Worsening after initial improvement 3
• Patient has high-risk conditions (chronic lung disease, heart disease, diabetes, immunosuppression, age ≥65) 1

Follow-Up and Safety Netting

Expected Clinical Course

Uncomplicated influenza typically resolves in 7 days, though cough, malaise, and fatigue may persist for weeks. 1, 5

Return Precautions - Advise Patient to Return Immediately If:

• Persistent fever beyond 5 days 3
• Worsening dyspnea or chest pain 3
• Confusion or altered mental status 3
• Inability to maintain hydration 1
• No improvement after 3-5 days 3

Medical Certificate

A medical certificate for work absence is appropriate given the acute infectious nature of this illness. Influenza is highly contagious, with viral shedding typically lasting around 5 days but potentially up to 10 days. 5 Recommend work absence until fever-free for 24 hours without antipyretics and symptoms are improving.

Critical Pitfalls to Avoid

• Do not assume all productive cough requires antibiotics - most acute bronchitis complicating influenza is viral 1
• Do not miss secondary bacterial pneumonia - examine chest carefully and have low threshold for chest X-ray if dyspnea or focal findings present 3
• Do not delay antiviral therapy if indicated - benefit decreases significantly after 48 hours 1, 4
• Do not dismiss severe headache - while common in influenza, persistent severe headache warrants consideration of rare complications like sinusitis with intracranial extension 6