What are the key considerations for treating and preventing common infectious diseases such as pneumonia, tuberculosis, and influenza?

Key Considerations for Treating and Preventing Common Infectious Diseases

Community-Acquired Pneumonia (CAP)

Outpatient Treatment

For previously healthy patients with non-severe CAP, oral amoxicillin is the recommended first-line therapy. 1

• Macrolide monotherapy (azithromycin, clarithromycin) should only be used in areas with documented low pneumococcal resistance rates 1
• For patients with risk factors or comorbidities, combination therapy with a β-lactam plus macrolide or a respiratory fluoroquinolone alone is preferred 1
• The first antibiotic dose must be administered in the emergency department before discharge to ensure prompt treatment initiation and improve outcomes 2

Hospitalized Non-ICU Patients

Two equally effective regimens exist: respiratory fluoroquinolone monotherapy OR β-lactam plus macrolide combination. 1, 3

• For penicillin-allergic patients, a respiratory fluoroquinolone is the preferred alternative 1
• Doxycycline can substitute for macrolides when combined with a β-lactam 1
• Switch to oral therapy when the patient is hemodynamically stable, clinically improving, afebrile for 24-48 hours, and able to take oral medications 1

Severe CAP (ICU Patients)

Immediate parenteral antibiotics with a β-lactam PLUS either azithromycin or a respiratory fluoroquinolone is mandatory. 1, 3

• For Pseudomonas risk factors, use an antipneumococcal, antipseudomonal β-lactam plus ciprofloxacin or levofloxacin 3
• For community-acquired MRSA risk, add vancomycin or linezolid 3
• Mortality in ICU patients approaches 40%, making aggressive early treatment critical 3

Duration and Special Pathogens

• Non-severe CAP: 5-7 days of therapy 1
• Severe CAP without identified pathogen: 10 days 1
• Legionella pneumonia requires 10-21 days of treatment (shorter for azithromycin due to long half-life), with azithromycin or fluoroquinolones (moxifloxacin, gatifloxacin, levofloxacin) recommended for severe disease 4

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Influenza

Antiviral Treatment

Neuraminidase inhibitors (oseltamivir, zanamivir) are the only recommended antivirals, as M2 inhibitors (amantadine, rimantadine) face widespread resistance. 4

• Treatment must begin within 48 hours of symptom onset to be effective 4
• Oseltamivir 75 mg twice daily for 5 days is the standard regimen 4
• Treatment beyond 48 hours is not recommended for uncomplicated influenza but may reduce viral shedding in hospitalized patients 4
• Early antiviral treatment reduces lower respiratory tract complications and antibiotic usage 4

Bacterial Superinfection

Empiric antibacterial therapy must target S. pneumoniae, S. aureus, and H. influenzae—the most common secondary pathogens. 4

• Appropriate agents include cefotaxime, ceftriaxone, respiratory fluoroquinolones, or amoxicillin-clavulanate 4
• Reserve vancomycin or linezolid for confirmed CA-MRSA or compatible clinical presentation (shock, necrotizing pneumonia) 4
• Legionella, Chlamydophila, and Mycoplasma are NOT important causes of post-influenza bacterial pneumonia 4

Avian Influenza (H5N1)

• Patients with influenza-like illness and poultry exposure in H5N1-endemic areas require testing 4
• Use droplet precautions and N-95 respirators until H5N1 is ruled out 4
• Treat with oseltamivir plus antibacterials targeting S. pneumoniae and S. aureus 4

Prevention

Annual influenza vaccination is the cornerstone of prevention, particularly for elderly persons and those with chronic cardiopulmonary disease. 4

• Influenza causes an average of 36,155 respiratory and circulatory deaths annually in the United States, with 80-90% occurring in persons ≥65 years 4
• High-risk groups include elderly, immunosuppressed, and those with chronic diseases 4

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Tuberculosis (TB)

Clinical Recognition

TB remains a social disease inextricably linked with poverty and requires a holistic approach beyond biomedical treatment. 4

• Acute tuberculous pneumonia can mimic community-acquired pneumonia, leading to dangerous treatment delays 5
• Rapid and accurate diagnosis is crucial to prevent transmission and deterioration 5
• Consider TB in patients with persistent pneumonia despite appropriate antibiotics, especially with risk factors (diabetes, immunosuppression, endemic exposure) 6

Treatment Considerations

• Standard four-drug therapy (isoniazid, rifampicin, ethambutol, pyrazinamide) is required 6
• Be vigilant for TB reactivation in patients receiving corticosteroids for severe pneumonia, even when antibiotics are administered 6
• Social determinants (poverty, housing, healthcare access) must be addressed for effective TB control 4

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Viral Pneumonias (Other)

Specific Viral Pathogens

Parenteral acyclovir is indicated for varicella-zoster virus or herpes simplex virus pneumonia. 4

• No proven antiviral treatment exists for parainfluenza, RSV, adenovirus, metapneumovirus, SARS, or hantavirus pneumonias 4
• Maintain high suspicion for bacterial superinfection in all viral pneumonias 4
• RSV antigen tests are insensitive in adults and not generally recommended 4

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Nosocomial Pneumonia Prevention

Key Prevention Strategies

Traditional measures include decreasing aspiration, preventing cross-contamination via hand hygiene, appropriate disinfection of respiratory devices, and vaccination. 4

• Mechanically ventilated patients are at highest risk for nosocomial pneumonia 4
• Most bacterial nosocomial pneumonias occur by aspiration of colonizing bacteria from the oropharynx 4
• Legionella and Aspergillus pneumonias often result from inhalation of contaminated aerosols 4
• RSV transmission occurs via contaminated hands touching conjunctivae or nasal mucosa 4

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Critical Pitfalls to Avoid

• Never delay antibiotics in CAP patients—administer the first dose in the ED 2
• Do not use amantadine or rimantadine for influenza due to widespread resistance 4
• Do not assume atypical pathogens are covered—always include macrolide or fluoroquinolone coverage for hospitalized CAP patients 1, 3
• Do not miss TB in patients with persistent pneumonia, especially those receiving steroids 6
• Do not empirically cover MRSA or Pseudomonas unless validated risk factors are present 3