What is the recommended treatment for patients diagnosed with influenza and pneumonia, particularly those at high risk of complications?

Treatment of Influenza and Pneumonia

For patients with influenza and pneumonia, initiate oseltamivir 75 mg orally twice daily for 5 days immediately upon diagnosis, combined with antibiotics targeting both typical and atypical pathogens—specifically co-amoxiclav or a tetracycline plus a macrolide for severe cases, or co-amoxiclav/tetracycline alone for non-severe cases. 1

Antiviral Therapy: Immediate Initiation

Oseltamivir should be started as soon as possible in all patients with influenza-related pneumonia, regardless of symptom duration. 1, 2

• Standard dosing is oseltamivir 75 mg orally every 12 hours for 5 days 1
• Reduce dose to 75 mg once daily if creatinine clearance is less than 30 mL/minute 1
• Severely ill hospitalized patients may benefit from antiviral treatment even when started more than 48 hours after symptom onset, particularly if immunocompromised 1, 2
• Immunocompromised patients and the very elderly may warrant treatment despite lack of documented fever 1

Critical pitfall: Do not delay antiviral therapy while awaiting virological confirmation in hospitalized patients with suspected influenza-related pneumonia. 3, 4

Antibiotic Selection: Severity-Based Approach

Non-Severe Influenza-Related Pneumonia

Most patients can be treated with oral antibiotics as outpatients. 1, 2

• First-line: Co-amoxiclav 625 mg three times daily OR doxycycline 200 mg loading dose, then 100 mg once daily 1
• Alternative (penicillin allergy): Clarithromycin 500 mg twice daily OR erythromycin 500 mg four times daily 1
• Levofloxacin or moxifloxacin are alternative fluoroquinolones with activity against S. pneumoniae and S. aureus 1
• Antibiotics must be administered within 4 hours of admission 1, 2

Severe Influenza-Related Pneumonia

Immediate parenteral combination therapy is mandatory for severe pneumonia. 1, 2, 3

• Preferred regimen: IV co-amoxiclav OR cefuroxime (2nd generation cephalosporin) OR cefotaxime (3rd generation cephalosporin) PLUS IV clarithromycin or erythromycin 1, 3
• Alternative: IV levofloxacin (the only IV fluoroquinolone licensed in the UK) plus a broad-spectrum β-lactamase stable antibiotic or macrolide 1
• Administer antibiotics immediately after diagnosis—do not delay 1, 2, 3

Rationale for combination therapy: Influenza-related pneumonia requires coverage for S. pneumoniae, S. aureus (including methicillin-susceptible strains), H. influenzae, and atypical pathogens (Mycoplasma, Chlamydophila). 1, 2

Antibiotic Duration and De-escalation

• Switch from IV to oral antibiotics once clinically improving and afebrile for 24 hours, with no contraindication to oral route 1, 3
• Total antibiotic duration: 7 days for non-severe pneumonia; 10 days for severe pneumonia 1, 3

High-Risk Populations Requiring Aggressive Treatment

Patients at high risk of complications should receive both antivirals and antibiotics even with lower respiratory features alone (without confirmed pneumonia). 1

High-risk groups include: 1

• Children aged <2 years (especially <6 months)
• Adults aged ≥65 years
• Pregnant or postpartum women (within 2 weeks of delivery)
• Chronic pulmonary disease (including asthma), cardiovascular disease (except hypertension alone), renal, hepatic, hematologic, metabolic (including diabetes), or neurologic conditions
• Immunosuppression (medication-induced or HIV)

Monitoring and Follow-Up

Patients should be reviewed 24 hours prior to discharge. 1 Consider continued hospitalization if ≥2 of the following unstable factors are present: 1

• Temperature >37.8°C
• Heart rate >100/min
• Respiratory rate >24/min
• Systolic blood pressure <90 mmHg
• Oxygen saturation <90%
• Inability to maintain oral intake
• Abnormal mental status

Follow-up clinical review is essential for all patients who suffered significant complications or worsening of underlying disease 1, 2, 4

Common Pitfalls to Avoid

• Do not withhold antibiotics in previously well adults with influenza-related pneumonia—they require empiric bacterial coverage 1
• Do not use antibiotics routinely for uncomplicated influenza (acute bronchitis without pneumonia) in previously well adults 1
• Do not delay treatment in severe cases—antibiotics should be given immediately, not within 4 hours 1, 2, 3
• Monitor for secondary bacterial pneumonia, which typically develops 4-5 days after initial influenza symptoms and may require adjustment of antibiotic coverage 2
• S. aureus is more common in influenza-related pneumonia than in routine community-acquired pneumonia, justifying broader empiric coverage 1, 2