What is the management approach for influenza, upper respiratory tract (URT) and lower respiratory tract (LRT) infections?

Management of Influenza, Upper Respiratory Tract (URT) and Lower Respiratory Tract (LRT) Infections

Initial Assessment and Triage

The critical first decision is determining whether the patient requires hospital admission or can be safely managed at home, based on specific clinical, biological, and radiological severity criteria. 1

Criteria for Hospital Referral

Immediate severity indicators requiring hospital admission include: 1

• Temperature <35°C or ≥40°C
• Heart rate ≥125 beats/min
• Respiratory rate ≥30 breaths/min
• Cyanosis
• Blood pressure <90/60 mmHg
• Confusion, drowsiness, or altered mental status
• Chest pain

Additional risk factors necessitating hospital consideration: 1

• Age >65 years
• Comorbidities (COPD, cardiovascular disease, diabetes, chronic liver/renal failure)
• Recent hospitalization within previous year
• Inability to manage at home (vomiting, social isolation, poor compliance likelihood)
• Failure of first-line antibiotic therapy

Laboratory/radiological criteria for hospital management: 1

• Leukopenia (<4,000 WBC/mL) or severe leukocytosis (>20,000 WBC/mL)
• PaO₂ <60 mmHg or PaCO₂ >50 mmHg on room air
• Acidosis (pH <7.3)
• Renal impairment (creatinine >1.2 mg/dL)
• Multilobar involvement, pleural effusion, or cavitation on chest radiograph

Management of Upper Respiratory Tract Infections (URIs)

Most URIs are viral and self-limiting; antibiotics should NOT be prescribed as they are ineffective and contribute to resistance. 2

Symptomatic Treatment for URIs

• Acetaminophen or ibuprofen for pain, fever, and inflammation 2
• Adequate hydration and rest as supportive measures 2
• Saline nasal irrigation for minor improvement in nasal symptoms 2
• Oral decongestants if no contraindications exist 2

Critical Pitfall to Avoid

Discolored nasal discharge alone does NOT indicate bacterial infection—it reflects inflammation, not bacterial etiology. 2 Antibiotics should not be prescribed based on this finding alone.

Safety Netting for Home-Managed URIs

Patients should return if: 2

• Symptoms persist beyond 3 weeks
• Fever exceeds 4 days
• Dyspnea worsens
• Patient stops drinking or consciousness decreases

Management of Lower Respiratory Tract Infections (LRTIs)

Home Management of LRTIs

For patients without severity criteria, aminopenicillin (amoxicillin 500-1000 mg every 8 hours) is the first-choice antibiotic for 5-7 days. 1, 3 This must always cover Streptococcus pneumoniae, the most common bacterial pathogen. 1, 3

Alternative antibiotics for home management: 1, 3

• Amoxicillin-clavulanate for patients with risk factors for beta-lactamase producing organisms (chronic lung disease, recent antibiotic use, high local resistance)
• Macrolides (clarithromycin 250-500 mg twice daily) for penicillin allergy or suspected atypical pathogens
• Tetracyclines (doxycycline 100 mg twice daily) for penicillin allergy
• Third-generation quinolones reserved for treatment failures or complicated cases

Important caveat: Many LRTIs are viral and self-limiting; antibiotics should only be used when bacterial infection is suspected based on clinical features (purulent sputum, focal chest signs, systemic inflammatory response). 1, 3

Hospital Management of LRTIs

For hospitalized patients not requiring ICU: 3

• Second-generation cephalosporins (IV cefuroxime 750-1500 mg every 8 hours)
• Third-generation cephalosporins (IV cefotaxime 1 g every 8 hours or IV ceftriaxone 1 g daily)
• IV benzylpenicillin or IV amoxicillin (1 g every 6 hours)

For ICU patients with severe LRTI: 3

• Combination therapy with second or third-generation cephalosporin PLUS either a second-generation quinolone OR a macrolide

Investigations for Hospitalized LRTI Patients

Routine investigations: 1

• Chest radiograph (posteroanterior in all patients)
• Peripheral blood white cell count
• Serum biochemistry (sodium, potassium, glucose, urea, creatinine)
• Arterial blood gases or pulse oximetry

Additional investigations for specific scenarios: 1

• Sputum sampling (after mouth-washing) for patients able to expectorate purulent samples who have not received prior antibiotics—results valid only with >25 polymorphonuclear cells and <10 squamous epithelial cells per high-power field 1
• Blood cultures for patients with temperature >38°C or suspected severe infection 1
• Endotracheal aspirate for mechanically ventilated patients 1

Management of Influenza

Antiviral Treatment

For severe influenza requiring hospitalization, oseltamivir 75 mg twice daily for 5 days is conditionally recommended and should be initiated as soon as possible. 4, 5, 6 Observational studies demonstrate that earlier initiation of antiviral treatment in critically ill patients is associated with survival benefit. 6

For non-severe influenza with high risk of severe illness (age >65, comorbidities, immunosuppression), baloxavir is conditionally recommended. 5 Antivirals are not recommended if risk is low. 5

For prophylaxis in asymptomatic persons exposed to seasonal influenza who would be at very high risk of hospitalization, baloxavir or oseltamivir are conditionally recommended. 5

Oxygen Therapy for Influenza Patients

Continuous oxygen therapy is indicated for: 1

• PaO₂ <8 kPa (60 mmHg)
• Hypotension with systolic BP <100 mmHg
• Metabolic acidosis with bicarbonate <18 mmol/L
• Respiratory distress with respiratory rate >30/min

Target oxygen saturation: Maintain PaO₂ >8 kPa or SaO₂ >92%. 1 High concentrations of oxygen (≥35%) are indicated unless complicated by severe COPD with CO₂ retention. 1

For COPD patients with potential CO₂ retention: Start with low oxygen concentrations (24-28%) and titrate based on repeated arterial blood gas measurements, keeping SaO₂ >90% without arterial pH falling below 7.35. 1

Antibiotic Use in Influenza

There is a strong recommendation AGAINST routine antibiotic use in influenza if bacterial co-infection is unlikely. 5 Antibiotics are over-prescribed in influenza patients even without bacterial infection signs. 7

Antibiotics should only be prescribed for influenza patients when bacterial co-infection is suspected, based on: 1

• Purulent sputum production
• Focal chest signs on examination
• Radiographic evidence of pneumonia
• Failure to improve or clinical deterioration after initial viral phase

Common bacterial co-pathogens in influenza: 1, 7

• Streptococcus pneumoniae (most common)
• Staphylococcus aureus
• Haemophilus influenzae
• Gram-negative enteric bacilli (in institutionalized elderly)

Corticosteroids in Influenza

Adjunctive corticosteroid treatment is NOT recommended for hospitalized influenza patients, including critically ill patients, unless clinically indicated for another reason (asthma/COPD exacerbation, septic shock). 6 Observational data suggest potential harms. 6

Diagnostic Testing for Influenza

Molecular tests (RT-PCR, nucleic acid amplification tests) are recommended for influenza testing in hospitalized patients. 5, 6 Antigen detection assays are not recommended in critically ill patients due to lower sensitivity. 6

For critically ill patients with lower respiratory tract disease, test endotracheal aspirate (preferentially) or bronchoalveolar lavage fluid by molecular assay, as upper respiratory tract specimens may be falsely negative despite ongoing lower respiratory tract viral replication. 6

Common Pitfalls to Avoid

• Prescribing antibiotics for viral URIs or uncomplicated influenza (ineffective and promotes resistance) 2, 5, 7
• Assuming purulent nasal discharge indicates bacterial infection (it reflects inflammation only) 2
• Using antigen detection assays in critically ill patients (insufficient sensitivity; use molecular tests) 6
• Routine corticosteroid use in influenza (observational data suggest harm) 6
• Overuse of fluoroquinolones (reserve for treatment failures or complicated cases to prevent resistance) 3
• Delaying antiviral therapy in severe influenza (earlier initiation associated with greater benefit) 6
• Failing to reassess patients within 48-72 hours if not improving on initial therapy 2