What are the recommended treatments for influenza (flu) versus the common cold in an otherwise healthy adult?

Treatment of Influenza vs Common Cold in Healthy Adults

For influenza, treat with oseltamivir 75 mg twice daily for 5 days if the patient presents within 48 hours of symptom onset with fever >38°C; for the common cold, use only symptomatic treatment with analgesics, zinc, or nasal decongestants—antibiotics are not indicated for either condition unless bacterial complications develop.

Key Distinction: Influenza Has Specific Antiviral Treatment, Common Cold Does Not

The fundamental difference in management is that influenza is caused by influenza virus and has effective antiviral medications, while the common cold (caused by rhinoviruses and other viruses) has no specific antiviral therapy and requires only symptomatic management 1, 2.

Influenza Treatment Algorithm

When to Treat with Antivirals

Antiviral treatment criteria (all three must be present) 3, 4:

• Acute influenza-like illness (fever, cough, myalgias, malaise)
• Fever >38°C
• Symptomatic for ≤48 hours

Oseltamivir dosing: 75 mg every 12 hours for 5 days 3, 4, 5

• Reduce to 75 mg once daily if creatinine clearance <30 mL/min
• Greatest benefit when started within 24 hours of symptom onset 2

Important Caveats for Antiviral Use

Exceptions to the 48-hour rule 3, 4:

• Immunocompromised or very elderly patients may benefit even without documented fever
• Severely ill hospitalized patients may benefit from treatment started >48 hours after onset, though evidence is limited

Do NOT routinely use antivirals for uncomplicated influenza in otherwise healthy adults who present after 48 hours—the benefit is minimal 2.

When Antibiotics Are Indicated for Influenza

Previously well adults with influenza do NOT routinely require antibiotics unless pneumonia develops 3, 4.

Consider antibiotics when 3, 5:

• Worsening symptoms develop (recrudescent fever or increasing dyspnea)
• Severe disease at presentation (extensive pneumonia, respiratory failure, hypotension)
• Patient deteriorates after initial improvement

Antibiotic choices for influenza-related pneumonia 3, 4:

• Non-severe pneumonia: Co-amoxiclav or tetracycline orally
• Severe pneumonia: IV co-amoxiclav or 2nd/3rd generation cephalosporin (cefuroxime/cefotaxime) PLUS macrolide (clarithromycin/erythromycin)
• Administer within 4 hours of admission for pneumonia

Common Cold Treatment

No antiviral medications are effective for the common cold 1, 6.

Effective Symptomatic Treatments for Adults

Proven effective 1, 6:

• Over-the-counter analgesics (acetaminophen, NSAIDs) for pain and fever
• Zinc (acetate or gluconate lozenges) started within 24 hours—modestly reduces duration
• Nasal decongestants (pseudoephedrine, phenylephrine) for congestion
• Intranasal ipratropium for rhinorrhea

Probably effective 6:

• Echinacea purpurea preparations
• Nonsteroidal anti-inflammatory drugs

Ineffective Treatments to Avoid

Do NOT use 1, 6:

• Antibiotics (strong recommendation against—no benefit, potential harm)
• Antihistamines alone
• Intranasal corticosteroids
• Codeine for cough
• Steam inhalation
• Echinacea angustifolia (different from E. purpurea)

Critical Clinical Pitfalls

Antibiotic Misuse

The most common error is prescribing antibiotics for viral upper respiratory infections. There is a strong recommendation against antibiotics for uncomplicated influenza or common cold 3, 4, 5, 1. Only use antibiotics when bacterial complications are suspected based on clinical deterioration, persistent high fever, or evidence of pneumonia.

Distinguishing Influenza from Common Cold Clinically

Influenza characteristics 2:

• Abrupt onset of high fever (>38°C)
• Prominent systemic symptoms (myalgias, chills, severe malaise)
• More severe illness overall

Common cold characteristics 1:

• Gradual onset
• Predominantly nasal symptoms (congestion, rhinorrhea)
• Mild or absent fever
• Less severe systemic symptoms

Timing Is Critical for Influenza Treatment

Antiviral benefit diminishes rapidly after 48 hours of symptom onset. The greatest benefit occurs when treatment starts within 24 hours 2. Do not delay treatment waiting for laboratory confirmation in high-risk situations.

Laboratory Testing Considerations

For most outpatient influenza cases, clinical diagnosis is sufficient and laboratory testing is not necessary 2. Reserve testing for hospitalized patients, those requiring treatment decisions, or when diagnosis is uncertain 5.