Viral Pneumonia

1. History

• Key HPI questions: Onset and duration of cough (productive vs. dry), dyspnea, fever/chills, pleuritic chest pain, sputum character, hemoptysis
• Symptom characterization: Viral pneumonia typically presents with gradual onset of dry cough, low-grade fever (<38.5°C), myalgias, and malaise, often preceded by upper respiratory prodrome (rhinorrhea, sore throat)[1-2]
• Timing/triggers: Seasonal patterns — RSV and influenza peak in late autumn/winter; rhinovirus in autumn/spring. Ask about sick contacts, recent travel, congregate living[2]
• Associated symptoms: Rhinorrhea, headache, myalgias, anosmia/ageusia (suggestive of COVID-19), wheezing, diarrhea (some viral etiologies)[1]
• Important negatives: Absence of purulent sputum, rigors, and pleuritic chest pain makes bacterial etiology less likely; however, clinical features alone cannot reliably distinguish viral from bacterial pneumonia[2]

2. Alarm Features

• SpO₂ <93% on room air, respiratory rate >30 breaths/min, or severe respiratory distress[3]
• Hemodynamic instability (SBP <90 mmHg) or need for vasopressors[4]
• Altered mental status / new confusion[4-5]
• Multilobar infiltrates on imaging[4]
• Signs of organ dysfunction: oliguria, thrombocytopenia (platelets <100,000), leukopenia (WBC <4,000)[4]
• ATS/IDSA severe CAP criteria: 1 major criterion (mechanical ventilation or septic shock requiring vasopressors) OR ≥3 minor criteria warrants ICU admission[4-5]
• Rapid clinical deterioration despite supportive care
• Hemoptysis or signs of secondary bacterial superinfection (new purulent sputum, rising procalcitonin)

3. Medications

Influenza-specific antivirals

• Oseltamivir 75 mg PO BID × 5 days — first-line for influenza A/B; most benefit within 48 hours of symptom onset, but still recommended in severe/hospitalized cases beyond 48 hours[6-7]
• Baloxavir marboxil (Xofluza) — single-dose oral; FDA-approved for uncomplicated influenza within 48 hours in patients ≥5 years[8]
• Peramivir 600 mg IV single dose — option when oral/inhaled routes not feasible[8]
• Zanamivir inhaled — alternative, especially if oseltamivir resistance suspected[2]

COVID-19 antivirals

• Remdesivir (Veklury) — FDA-approved for hospitalized patients and high-risk outpatients with mild-to-moderate COVID-19[8]
• Nirmatrelvir/ritonavir (Paxlovid) for high-risk outpatients within 5 days of symptom onset
• RSV/other viruses: Largely supportive; ribavirin (aerosolized or IV) considered in immunocompromised patients with RSV, hMPV, or parainfluenza. Cidofovir for severe adenovirus in immunocompromised. Acyclovir for varicella pneumonia[2][4]
• Corticosteroids: Dexamethasone reduces mortality in severe COVID-19 requiring supplemental O₂; role in non-COVID viral pneumonia is controversial and not routinely recommended[1-2]
• Antibiotics: Should be deferred if viral etiology is confirmed and bacterial coinfection is low suspicion (procalcitonin ≤0.25 ng/mL); IDSA suggests antiviral therapy alone in this setting[9]
• Contraindicated/cautions: Avoid unnecessary antibiotics — up to 20% of hospitalized patients receiving antibacterials experience adverse events, and each additional day increases resistant organism risk by ~7%[9]

4. Diet

• Hydration: Adequate oral fluid intake is essential; IV fluids for patients unable to maintain oral intake or with hemodynamic compromise
• Nutritional support: Malnourished and elderly patients benefit from individualized nutritional intervention programs (high protein 1.2–1.5 g/kg/day, energy 25–30 kcal/kg/day), which have been shown to reduce pneumonia readmission rates by up to 77% in malnourished older adults[10-11]
• Micronutrients: Vitamin C supplementation may have modest benefit in patients with deficiency; vitamins C and D, zinc, and selenium highlighted as potentially beneficial in respiratory viral infections, though supplementation has not been linked to prevention[12-13]
• Acute phase: Small, frequent, calorie-dense meals; avoid aspiration risk in patients with altered mental status or severe dyspnea

5. Review of Systems

• Respiratory: Cough (dry vs. productive), dyspnea, wheezing, chest tightness, hemoptysis
• Constitutional: Fever, chills, rigors, fatigue, myalgias, night sweats, weight loss
• ENT: Rhinorrhea, sore throat, anosmia, ageusia, sinus congestion
• GI: Nausea, vomiting, diarrhea (common with COVID-19, adenovirus)
• Cardiac: Chest pain, palpitations (screen for myocarditis complication)
• Neurologic: Confusion, headache, altered mental status
• Skin: Rash (consider measles, varicella, adenovirus)

6. Collateral History and Family History

• Collateral: Vaccination status (influenza, COVID-19, pneumococcal), sick contacts, daycare/school/nursing home exposure, recent travel (MERS-endemic areas, avian influenza regions), occupational exposures (healthcare workers, poultry workers)
• Family history: Immunodeficiency syndromes, household members with respiratory illness
• Social context: Congregate living (shelters, dormitories, military barracks — adenovirus outbreaks), smoking status, substance use, ability to comply with outpatient treatment, home support adequacy[14]

7. Risk Factors

• Age extremes: Elderly (≥65 years) and young children at highest risk[1][9]
• Immunosuppression: Transplant recipients, chemotherapy, HIV/AIDS, chronic corticosteroid use — at risk for severe disease and broader viral etiologies (CMV, HSV, adenovirus reactivation)[4][15]
• Chronic lung disease: COPD, asthma, bronchiectasis, cystic fibrosis[9]
• Smoking[9]
• Comorbidities: Diabetes, heart failure, chronic kidney disease, liver disease, obesity
• Unvaccinated status against influenza, COVID-19, or measles
• Pregnancy
• Nursing home/long-term care facility residence

8. Differential Diagnosis

• Bacterial pneumonia (S. pneumoniae, H. influenzae, S. aureus) — higher fever, rigors, purulent sputum, lobar consolidation, elevated procalcitonin[2][16]
• Atypical pneumonia (Mycoplasma, Chlamydophila, Legionella) — subacute onset, younger patients, extrapulmonary symptoms; procalcitonin may be normal with Mycoplasma[16-17]
• Acute bronchitis — cough without radiographic infiltrate
• Pulmonary embolism — pleuritic chest pain, dyspnea, tachycardia, risk factors for VTE
• Heart failure exacerbation — bilateral infiltrates, elevated BNP, orthopnea, peripheral edema
• Hypersensitivity pneumonitis / eosinophilic pneumonia — exposure history, peripheral eosinophilia
• Fungal pneumonia (Coccidioides, Histoplasma, Pneumocystis) — geographic/immune risk factors[9]
• Tuberculosis — chronic cough, night sweats, weight loss, upper lobe cavitary disease, endemic exposure
• COVID-19 — cannot-miss; test all patients with CAP when circulating in community[9]

9. Past Medical History

• Prior pneumonia episodes and hospitalizations
• Chronic respiratory disease (COPD, asthma, ILD)
• Immunosuppressive conditions or medications
• Prior intubation/mechanical ventilation
• Vaccination history (influenza, COVID-19, pneumococcal, measles)
• Recent antibiotic use (risk for resistant organisms)
• Splenectomy (encapsulated organism risk)
• Swallowing dysfunction or aspiration risk

10. Physical Exam

• Vital signs: Temperature (fever or hypothermia <36°C), tachypnea (RR >30 is a minor severity criterion), tachycardia, hypotension, SpO₂ (critical for severity assessment)[4][18]
• Pulmonary: Crackles/rales, rhonchi, decreased breath sounds, egophony, dullness to percussion (consolidation), wheezing (more common in viral)[16][18]
• General: Assess work of breathing, accessory muscle use, ability to speak in full sentences
• Cardiac: Tachycardia, new murmur, gallop (concern for myocarditis)
• Skin: Cyanosis, mottling (shock), rash (varicella, measles)
• Neurologic: Mental status assessment — confusion is a severity criterion[4]
• Expected vs. concerning: Diffuse bilateral crackles with wheezing more typical of viral; focal consolidation with bronchial breath sounds more suggestive of bacterial, though significant overlap exists[2]

11. Lab Studies

Recommended initial labs (hospitalized patients)

• CBC with differential — lymphopenia common in viral pneumonia; leukocytosis with left shift suggests bacterial[2]
• BMP (BUN, creatinine — severity scoring and organ dysfunction)
• Procalcitonin — low levels (<0.25 ng/mL) support viral etiology and may allow deferral of antibiotics; >0.5 ng/mL supports bacterial infection, though NPV is more reliable than PPV[9][16]
• CRP — elevated in both viral and bacterial, but higher levels (>30 mg/L) strengthen pneumonia diagnosis[18]
• Lactate (if sepsis concern)
• Blood cultures × 2 (before antibiotics if bacterial coinfection suspected)
• Hepatic function panel, troponin (if myocarditis concern)

Microbiologic testing

• Respiratory viral panel (multiplex PCR) — identifies influenza, RSV, SARS-CoV-2, adenovirus, parainfluenza, hMPV, rhinovirus[15][19]
• Rapid influenza and COVID-19 testing for all patients with CAP when these viruses are circulating[9]
• Sputum culture if bacterial coinfection suspected
• Urine antigens (Legionella, S. pneumoniae) in hospitalized patients
• Monitoring: Serial procalcitonin can guide antibiotic de-escalation[16]

12. Imaging

• First-line: Chest X-ray (PA and lateral) — required to confirm pneumonia diagnosis; viral pneumonia classically shows bilateral, diffuse interstitial or ground-glass opacities rather than focal lobar consolidation[20-21]
• CT chest: More sensitive than CXR; indicated when CXR is negative but clinical suspicion remains high, or for complications (abscess, empyema, PE). Ground-glass opacity (GGO) is an independent predictor of viral etiology (OR 4.68)[5][16][21]
• Lung ultrasound: Pooled sensitivity 92%, specificity 89% — superior to CXR; useful at bedside in ED/ICU; dynamic air bronchograms are pathognomonic for pneumonia[5]
• Imaging patterns by virus: Influenza — bilateral GGO and consolidation; COVID-19 — peripheral, bilateral GGO with crazy-paving; RSV — peribronchial thickening, air trapping; adenovirus — multifocal consolidation[20]
• When imaging is unnecessary: Low-risk outpatients with classic viral URI symptoms and no hypoxia or exam findings of consolidation may not require imaging[18]

13. Special Tests

Severity scoring systems

• Low risk: consider outpatient treatment. Patients with a CURB-65 score of 0 or 1 generally have a low risk of mortality and may be suitable for outpatient management.[22-23] However, clinical judgment should be used as additional factors such as hypoxemia, failure of outpatient therapy, or cardiovascular events may necessitate hospitalization.[22]
• PSI (Pneumonia Severity Index): Preferred by ATS/IDSA for site-of-care decisions; classes I–III generally safe for outpatient management[9][14]
• SMART-COP: Predicts need for intensive respiratory or vasopressor support[5]
• Point-of-care testing: Rapid antigen tests for influenza and COVID-19; POCT procalcitonin
• Multiplex respiratory PCR panels — gold standard for viral pathogen identification[15][19]
• Bronchoscopy with BAL: Consider in immunocompromised patients or when upper respiratory sampling is negative but clinical suspicion remains high[19]

14. ECG

• Indications: Obtain ECG in patients with chest pain, tachycardia, palpitations, or hemodynamic instability to evaluate for myocarditis or other cardiac complications
• Viral pneumonia-associated myocarditis findings: Sinus tachycardia, diffuse ST-segment elevation (without reciprocal changes), T-wave inversions (especially inferior/lateral leads), PR depression, low QRS voltage, new conduction abnormalities[24-25]
• Dangerous patterns: New AV block (2nd or 3rd degree), wide QRS ≥120 ms, ventricular tachycardia, prolonged QT — raise suspicion for giant cell myocarditis or fulminant myocarditis requiring urgent cardiology consultation[25-26]
• COVID-19 specific: QT prolongation (especially if on QT-prolonging medications), atrial fibrillation, ventricular arrhythmias[27]
• Sinus tachycardia alone is common and nonspecific in febrile pneumonia patients

15. Assessment

• Viral pneumonia accounts for up to 40% of CAP cases with an identified pathogen; influenza, rhinovirus, and SARS-CoV-2 are the most common viral etiologies[9][17]
• No clinical algorithm reliably distinguishes viral from bacterial pneumonia; the combination of rhinorrhea, GGO on imaging, lower procalcitonin, and lymphocyte-predominant differential favors viral etiology[2][21]
• Severity stratification should use CURB-65 or PSI supplemented by clinical judgment; ATS/IDSA severe CAP criteria guide ICU admission[4-5][16]
• Typical presentation: Gradual onset, dry cough, low-grade fever, bilateral interstitial infiltrates, preceded by URI prodrome
• Atypical/severe presentations: Rapid progression to ARDS (especially influenza H1N1, COVID-19, adenovirus type 14), secondary bacterial superinfection (S. aureus with influenza), invasive aspergillosis in severe viral pneumonia on steroids[5]
• Complications: ARDS, sepsis, myocarditis, secondary bacterial pneumonia, empyema, multiorgan dysfunction
• The following figure illustrates the pathogenesis of CAP from inflammatory response to organ dysfunction, including the ATS/IDSA criteria for severe CAP:

16. Treatment Plan

• Initial stabilization: Supplemental O₂ to maintain SpO₂ ≥92% (≥95% in pregnancy); high-flow nasal cannula or NIV for moderate-severe hypoxemia; intubation for refractory respiratory failure

Antiviral therapy

• Influenza → oseltamivir 75 mg PO BID × 5 days (start empirically if influenza suspected, do not wait for test results in severe illness)[6-7]
• COVID-19 → remdesivir (hospitalized), nirmatrelvir/ritonavir (high-risk outpatients)
• Other viruses → primarily supportive; ribavirin or cidofovir in select immunocompromised patients[2][4]
• Antibiotics: Defer if confirmed viral etiology with low procalcitonin (≤0.25 ng/mL) and low suspicion for bacterial coinfection. If bacterial coinfection cannot be excluded, treat empirically per ATS/IDSA guidelines with early de-escalation when bacterial infection is ruled out[5][9]
• Corticosteroids: Dexamethasone 6 mg daily × 10 days for COVID-19 requiring supplemental O₂; systemic corticosteroids within 24 hours may reduce 28-day mortality in severe CAP. Not routinely recommended for non-COVID viral pneumonia[1-2][9]
• Supportive care: IV fluids (avoid overhydration), antipyretics, VTE prophylaxis in hospitalized patients, nutritional support for malnourished patients[10-11]

17. Disposition

• Outpatient management: CURB-65 score 0–1 or PSI class I–III, SpO₂ >92% on room air, able to tolerate oral medications, adequate home support, no alarm features[9][14][16]
• Admission criteria: CURB-65 ≥2, PSI class IV–V, hypoxemia requiring supplemental O₂, inability to maintain oral intake, significant comorbidities, failed outpatient therapy, inadequate home support or social determinants precluding safe discharge[9][14]
• ICU admission: 1 major ATS/IDSA criterion (vasopressor requirement or mechanical ventilation) OR ≥3 minor criteria[4][28]
• Observation: Consider for borderline cases (CURB-65 = 2, PSI class III) — reassess within 24 hours
• Specialist consultation triggers: Pulmonology for refractory hypoxemia or ARDS; infectious disease for immunocompromised patients or unusual viral pathogens; cardiology if myocarditis suspected

18. Follow Up / Return Precautions

• Follow-up timing: Outpatients should be reassessed within 48–72 hours if not improving; follow-up CXR at 6–8 weeks to confirm radiographic resolution (especially in smokers and patients >50 years to exclude underlying malignancy)
• Clinical stability criteria for discharge: Temperature <37.8°C, HR <100, RR <24, SBP ≥90, SpO₂ ≥90% on room air, normal mental status, tolerating oral intake[17]
• Return precautions — instruct patients to return immediately for:
• Worsening shortness of breath or inability to catch breath at rest
• Persistent or worsening fever >72 hours despite treatment
• Chest pain, lightheadedness, or syncope
• Confusion or altered mental status
• Inability to keep down fluids
• Coughing up blood
• Expected recovery: Fever typically resolves within 2–4 days; cough may persist 2–4 weeks; fatigue may last several weeks. Failure to improve by 72 hours should prompt reassessment for complications, resistant organisms, or alternative diagnoses[17]
• Patient counseling: Hand hygiene, respiratory etiquette, isolation precautions during acute illness, smoking cessation, vaccination (influenza annually, COVID-19, pneumococcal per guidelines)

References

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23. Performance of the CURB-65 Score in Predicting Critical Care Interventions in Patients Admitted With Community-Acquired Pneumonia. — Ilg A, Moskowitz A, Konanki V, et al. Annals of Emergency Medicine. 2019.

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25. 2024 ACC Expert Consensus Decision Pathway on Strategies and Criteria for the Diagnosis and Management Of Myocarditis: A Report of the American College of Cardiology Solution Set Oversight Committee. — Drazner MH, Bozkurt B, Cooper LT, et al. Journal of the American College of Cardiology. 2025.

26. Recognition and Initial Management of Fulminant Myocarditis: A Scientific Statement From the American Heart Association. — Kociol RD, Cooper LT, Fang JC, et al. Circulation. 2020.

27. 2022 ACC Expert Consensus Decision Pathway on Cardiovascular Sequelae of COVID-19 in Adults: Myocarditis and Other Myocardial Involvement, Post-Acute Sequelae of SARS-CoV-2 Infection, and Return to Play: A Report of the American College of Cardiology Solution Set Oversight Committee. — Gluckman TJ, Bhave NM, Allen LA, et al. Journal of the American College of Cardiology. 2022.

28. Community-Acquired Pneumonia: Updated Recommendations From the ATS and IDSA. — Armstrong C. American Family Physician. 2020.