What is the recommended management of viral pneumonia in an adult?

Management of Viral Pneumonia in Adults

For adults with confirmed or suspected viral pneumonia, supportive care remains the cornerstone of management, with antiviral therapy reserved for specific pathogens—primarily influenza and varicella-zoster virus—when initiated early in the disease course.

---

Diagnostic Approach and Pathogen Identification

• Obtain respiratory specimens for viral testing (nasopharyngeal swab, sputum, or bronchoalveolar lavage) using rapid antigen detection or nucleic acid amplification tests (PCR) to identify influenza, respiratory syncytial virus (RSV), adenovirus, parainfluenza, human metapneumovirus, and coronaviruses. 1, 2
• Blood cultures and sputum Gram stain/culture should be collected before initiating antibiotics in all hospitalized patients to exclude bacterial superinfection or co-infection, which occurs in 18–38% of severe viral pneumonia cases. 1
• Chest radiography is mandatory to confirm pneumonia and assess severity; viral pneumonias typically show bilateral interstitial or patchy infiltrates, though radiographic patterns alone cannot reliably distinguish viral from bacterial etiologies. 1
• Consider influenza testing during winter months in patients presenting with high-grade fever, myalgias, cough, and respiratory symptoms, especially during peak influenza activity. 3
• RSV should be suspected in elderly patients with coryza, wheezing, low-grade fever, and patchy infiltrates during winter months, particularly if rapid influenza testing is negative. 3

---

Antiviral Therapy for Specific Viral Pathogens

Influenza Virus

• Initiate oseltamivir 75 mg orally twice daily within 48 hours of symptom onset for confirmed or suspected influenza A or B in hospitalized patients, as early treatment reduces lower respiratory tract complications and antibiotic usage rates. 1
• Oseltamivir is preferred over zanamivir in hospitalized patients due to its broad influenza spectrum, low resistance risk, and lack of bronchospasm risk. 1
• Continue oseltamivir for 5 days as the standard course; for hospitalized patients with influenza pneumonia, treatment may be extended beyond 48 hours of symptom onset to reduce viral shedding (median duration 4 days after hospitalization) from an infection-control standpoint. 1
• Do not use amantadine or rimantadine for influenza A treatment or prophylaxis in the United States, as circulating strains demonstrate widespread resistance to M2 inhibitors. 1
• Add empiric antibacterial therapy targeting Streptococcus pneumoniae and Staphylococcus aureus (the most common causes of secondary bacterial pneumonia after influenza) using cefotaxime, ceftriaxone, or a respiratory fluoroquinolone. 1

Avian Influenza A (H5N1)

• For suspected H5N1 infection (illness compatible with influenza plus known poultry exposure in endemic areas), initiate oseltamivir 75 mg twice daily for 5 days plus antibacterial agents targeting S. pneumoniae and S. aureus. 1
• Implement droplet precautions and respiratory isolation (N-95 respirators during aerosol-generating procedures) until H5N1 infection is ruled out. 1
• H5N1 strains are susceptible to neuraminidase inhibitors (oseltamivir and zanamivir) but resistant to adamantanes. 1

Varicella-Zoster Virus and Herpes Simplex Virus

• Administer intravenous acyclovir for varicella-zoster virus pneumonia or herpes simplex virus pneumonia in adults. 1

Respiratory Syncytial Virus, Parainfluenza, Adenovirus, and Other Viruses

• No antiviral treatment of proven value is available for RSV, parainfluenza virus, adenovirus, human metapneumovirus, SARS-associated coronavirus, or hantavirus pneumonia in immunocompetent adults. 1
• Ribavirin has been used for RSV and adenovirus in immunocompromised patients, but efficacy is not established in immunocompetent adults; it appears ineffective for hantavirus infection. 1, 4
• Supportive care remains the primary management strategy for these viral pneumonias, with close monitoring for bacterial superinfection. 1, 4, 5

---

Supportive Care and Monitoring

• Provide supplemental oxygen to maintain PaO₂ >8 kPa (60 mmHg) and SaO₂ >92%; high-flow oxygen is safe in uncomplicated viral pneumonia without chronic obstructive pulmonary disease. 1, 6
• Assess volume status and administer intravenous fluids as needed for dehydration or hemodynamic instability. 1, 6
• Monitor temperature, respiratory rate, pulse, blood pressure, mental status, and oxygen saturation at least twice daily in hospitalized patients to detect early deterioration. 1, 6, 7
• Nutritional support should be provided in prolonged illness. 1, 6
• Analgesics (paracetamol) should be used for pleuritic pain relief. 1

---

Management of Bacterial Superinfection

• Maintain a high clinical suspicion for bacterial superinfection in all patients with viral pneumonia, as secondary bacterial pneumonia is a major cause of morbidity and mortality. 1, 3
• Bacterial etiologies after influenza include S. pneumoniae, S. aureus (including MRSA), Haemophilus influenzae, and group A streptococci; Legionella, Chlamydophila, and Mycoplasma species are not important causes of post-influenza bacterial pneumonia. 1
• Empiric antibacterial therapy should include cefotaxime, ceftriaxone, or a respiratory fluoroquinolone to cover typical bacterial pathogens when superinfection is suspected. 1
• Add vancomycin or linezolid if MRSA is suspected (post-influenza pneumonia, cavitary infiltrates, prior MRSA infection/colonization, or recent hospitalization with IV antibiotics). 1

---

Duration of Therapy and Transition to Oral Agents

• Treat influenza with oseltamivir for 5 days as the standard course; extend to 14–21 days only for specific bacterial superinfections caused by Legionella, S. aureus, or Gram-negative enteric bacilli. 1, 6, 7
• Switch from IV to oral antibiotics (if bacterial superinfection is being treated) when the patient is hemodynamically stable, clinically improving, afebrile for 48–72 hours, able to ingest medications, and has normal gastrointestinal function—typically by hospital day 2–3. 1, 6, 7

---

Follow-Up and Prevention

• Schedule clinical review at 6 weeks for all hospitalized patients; obtain chest radiograph only if symptoms persist, physical signs remain abnormal, or the patient has high risk for underlying malignancy (smokers >50 years). 1, 6, 7
• Administer annual influenza vaccination to all patients, especially those with chronic medical illnesses and healthcare workers, to prevent influenza-related viral pneumonia. 1
• Pneumococcal polysaccharide vaccine should be offered to all adults ≥65 years and those with high-risk conditions to reduce the risk of bacterial superinfection. 1
• Smoking cessation should be a goal for all patients hospitalized with viral pneumonia who smoke. 1

---

Critical Pitfalls to Avoid

• Do not delay oseltamivir beyond 48 hours of symptom onset in outpatients with uncomplicated influenza, as efficacy is limited after this window; however, hospitalized patients with influenza pneumonia may benefit from treatment even beyond 48 hours. 1
• Do not use amantadine or rimantadine for influenza A in the United States due to widespread resistance. 1
• Do not assume viral pneumonia is self-limited; bacterial superinfection is common and requires empiric antibacterial therapy targeting S. pneumoniae and S. aureus. 1, 3
• Do not withhold antibacterial therapy in patients with confirmed viral pneumonia who develop new fever, worsening respiratory status, or radiographic progression, as these findings suggest bacterial superinfection. 1, 5
• Do not use ribavirin routinely for RSV or adenovirus pneumonia in immunocompetent adults, as efficacy is not established and the drug is reserved for compassionate use in immunocompromised patients. 1, 4