Pneumonia: Symptoms, Treatment and Prevention

What Is Pneumonia?

Hello, I am Dr. Emre Geçer. Pneumonia is an infectious inflammation of the alveoli (air sacs) and surrounding tissue of the lungs. As a result of the infection, the alveoli fill with inflammatory fluid, pus and cellular debris; this disrupts gas exchange, reducing oxygen uptake and impairing carbon dioxide elimination. Pneumonia is one of the most common causes of death from infectious disease worldwide and leads to significant mortality and morbidity, especially in children under 5 and adults over 65.

Types of Pneumonia

Pneumonia is classified according to where it was acquired and the patient's characteristics. This classification is critical for predicting the likely causative microorganisms and choosing the right treatment:

1. Community-Acquired Pneumonia (CAP)

Pneumonia that develops outside the hospital or within the first 48 hours of admission. It is the most common type of pneumonia. The most frequent causative agents are:

• Streptococcus pneumoniae (pneumococcus): The most common bacterial cause of community-acquired pneumonia. Classic lobar pneumonia with rust-colored sputum production is characteristic.
• Haemophilus influenzae: Common in people with COPD and chronic lung disease.
• Mycoplasma pneumoniae: Causes "atypical pneumonia" in young adults. A dry cough, headache and mild course are typical.
• Chlamydophila pneumoniae: Mild atypical pneumonia.
• Legionella pneumophila: Transmitted from contaminated water systems (air conditioning, showers). Can be severe; diarrhea, confusion and hyponatremia may accompany the illness.
• Viral agents: Influenza (flu virus), SARS-CoV-2, RSV, adenovirus. Viral pneumonias come to the fore especially during outbreaks.

2. Hospital-Acquired Pneumonia (HAP)

Pneumonia that develops 48 hours or more after hospital admission. It is caused by more resistant microorganisms than community-acquired pneumonia (MRSA, Pseudomonas aeruginosa, Klebsiella, Acinetobacter) and takes a more severe course. Mortality is high.

3. Ventilator-Associated Pneumonia (VAP)

Pneumonia that develops 48 hours or more after the start of mechanical ventilation. It is an important complication in intensive care units and is often caused by multidrug-resistant bacteria.

4. Aspiration Pneumonia

Aspiration pneumonia develops when oropharyngeal or gastric contents are aspirated into the lower airways. Patients with impaired consciousness, swallowing difficulty (dysphagia), GERD, alcoholism or stroke are at risk. Anaerobic bacteria are often involved.

Pathophysiology: What Happens in the Lungs?

Under normal conditions, the lungs are protected by several defense mechanisms: nasal hairs and mucus filter particles, the mucociliary system carries secretions upward, the cough reflex expels foreign matter and alveolar macrophages phagocytose microbes. Pneumonia develops when these defenses are overwhelmed or weakened.

When the causative agent reaches the alveoli, the inflammatory cascade begins: neutrophils and macrophages migrate to the area, cytokines are released, and edema and exudate (inflammatory fluid) accumulate in the alveoli. This process is described by the four classic pathological stages of pneumonia: congestion (day 1), red hepatization (days 2–3), gray hepatization (days 4–6) and resolution (healing).

Symptoms of Pneumonia

Typical Pneumonia Symptoms

• Fever and chills: Usually a high fever above 38.5 °C with shaking chills. Bacterial pneumonias tend to start abruptly with high fever.
• Cough: May be dry at first and become productive over time. Rusty-colored sputum is classic in pneumococcal pneumonia. Red, currant-jelly sputum may be seen in Klebsiella pneumonia.
• Shortness of breath (dyspnea): Ranges from mild to severe depending on the size of the affected lung area. Dyspnea may even occur at rest.
• Pleuritic chest pain: Sharp, stabbing chest pain that worsens with breathing and coughing. It is due to inflammation of the pleura (lung lining).
• Rapid breathing (tachypnea): Respiratory rate over 20 per minute.
• General malaise: Weakness, loss of appetite, muscle aches, headache.

Atypical Pneumonia Symptoms

Pneumonia caused by atypical agents such as Mycoplasma, Chlamydophila and Legionella often starts more insidiously:

• Dry, persistent cough (with little or no sputum)
• Low-grade fever
• Headache, muscle and joint pain
• Sore throat
• Physical examination findings may be milder than the widespread involvement seen on chest X-ray

Older Adults and Immunocompromised Individuals

In older adults, pneumonia may present not with classic fever and cough but with confusion (altered mental status), debility, loss of appetite and functional decline. The fever response may be blunted or absent. This can delay diagnosis.

Diagnostic Methods

Chest Radiograph (Chest X-ray)

The chest X-ray is the primary imaging modality for diagnosing pneumonia. Lobar consolidation (complete involvement of a lobe or segment), bronchopneumonia (patchy infiltrates) or interstitial pattern (in atypical pneumonias) may be seen. It is also valuable for showing complications (pleural effusion, abscess).

Laboratory Tests

• Complete blood count (CBC): Leukocytosis (elevated white cell count) and neutrophilia in bacterial pneumonia. White cell count may be normal or low in viral pneumonias.
• CRP (C-reactive protein): An inflammation marker; elevation supports infection.
• Procalcitonin: More specific than CRP for distinguishing bacterial from viral infection. It guides the start and stop of antibiotic therapy.
• Blood cultures: Taken in severe pneumonia to identify the organism and its antibiotic susceptibility.
• Sputum culture and Gram stain: For identifying the organism and detecting resistance.

Severity Scoring Systems

Scoring systems are used to decide whether to treat a patient as an outpatient, on a hospital ward or in intensive care:

• CURB-65 score: Confusion, Urea (>7 mmol/L), Respiratory rate (≥30/min), Blood pressure (systolic <90 or diastolic ≤60 mmHg) and age ≥65. Each parameter scores 1 point; 0–1 points outpatient, 2 points hospital admission, 3–5 points intensive care assessment.
• PSI (Pneumonia Severity Index): A more detailed scoring system including age, comorbidities, vital signs and laboratory values.

Treatment

Antibiotic Therapy

In bacterial pneumonia, empiric antibiotic therapy is started as soon as the diagnosis is made. The choice of treatment is determined by the type and severity of pneumonia and the patient's risk factors:

• Outpatient treatment (mild CAP): Amoxicillin alone or combined with a macrolide (azithromycin, clarithromycin). A macrolide or doxycycline may be preferred if an atypical pathogen is suspected.
• CAP requiring hospital admission: Beta-lactam (ampicillin–sulbactam or ceftriaxone) plus a macrolide, or monotherapy with a respiratory fluoroquinolone (moxifloxacin, levofloxacin).
• Severe CAP requiring intensive care: Beta-lactam plus macrolide, or beta-lactam plus fluoroquinolone. An anti-pseudomonal beta-lactam is added if there is a risk of Pseudomonas.
• Hospital-acquired pneumonia: Broad-spectrum empiric therapy covering anti-pseudomonal organisms and MRSA is started, then narrowed based on culture results.

Treatment duration is usually 5–7 days in community-acquired pneumonia and longer in complicated cases. Clinical improvement (fever defervescence, symptom relief) usually begins within 48–72 hours.

Supportive Treatment

• Adequate fluid intake and hydration
• Fever control (paracetamol, ibuprofen)
• Oxygen therapy (for hypoxemia)
• Adequate nutrition and rest
• Mechanical ventilation support in severe cases

Complications

Untreated or severe pneumonia can lead to serious complications:

• Parapneumonic effusion and empyema: Fluid (effusion) or pus (empyema) accumulation in the pleural space. Empyema usually requires chest tube drainage and prolonged antibiotic therapy.
• Lung abscess: Necrosis and pus collection within lung tissue. Anaerobic bacteria are common causes. Prolonged antibiotic therapy, sometimes surgical drainage, is required.
• Sepsis and septic shock: Infection spreading to the bloodstream, producing systemic inflammatory response syndrome and organ failure. Requires intensive care; mortality is high.
• ARDS (acute respiratory distress syndrome): Severe lung inflammation causing diffuse alveolar damage and profound hypoxemia. Requires mechanical ventilation and intensive care support.
• Bacteremia: Bacteria entering the bloodstream — can lead to distant infections such as meningitis and endocarditis.

Prevention

Pneumococcal Vaccine

Pneumococcal vaccination is one of the most effective ways to prevent pneumonia:

• PCV13 (conjugate vaccine): Provides protection against 13 pneumococcal serotypes. Routinely administered in the childhood vaccination program.
• PPSV23 (polysaccharide vaccine): Provides protection against 23 serotypes. Recommended for all adults over 65 and for at-risk groups with chronic disease.
• PCV20: A next-generation conjugate vaccine that provides broader serotype coverage.

Influenza (Flu) Vaccine

Annual flu vaccination is effective in preventing both primary viral pneumonia and post-influenza secondary bacterial pneumonia. It is particularly recommended for people over 65, those with chronic illness, healthcare workers and pregnant women.

General Preventive Measures

• Regular hand washing
• Smoking cessation (smoking impairs respiratory defense mechanisms)
• Oral hygiene (reduces the risk of aspiration pneumonia)
• Good control of chronic conditions (diabetes, COPD, heart failure)
• Adequate nutrition and sleep

Special Populations

Pneumonia in Older Adults

Pneumonia mortality in adults over 65 is markedly higher than in younger adults. Age-related decline in immune function (immunosenescence), a weaker cough reflex, swallowing difficulties and comorbidities increase the risk. Diagnosis may be delayed because of atypical presentation (absence of fever, confusion).

Pneumonia in Immunocompromised Individuals

Cancer patients on chemotherapy, organ transplant recipients, people living with HIV/AIDS and those on long-term immunosuppressive therapy are at risk of pneumonia from unusual organisms (Pneumocystis jirovecii, Aspergillus, CMV). Prophylactic treatment and close monitoring are important in this group.

Conclusion

Pneumonia is a serious lung infection that can largely be cured with correct, timely treatment but can become life-threatening if neglected. When symptoms such as fever, cough, sputum production, shortness of breath and chest pain develop, see a doctor without delay. Pneumococcal and influenza vaccines, smoking cessation, hand hygiene and healthy lifestyle habits are the cornerstones of pneumonia prevention. Older adults, those with chronic illness and those with weakened immunity should be especially careful and should not skip their vaccinations.

Wishing you healthy days.
Dr. Emre Geçer

References

• Murray & Nadel's Textbook of Respiratory Medicine, 7th Edition — Chapter: Pneumonia
• Harrison's Principles of Internal Medicine, 22nd Edition — Chapter: Pneumonia
• IDSA/ATS Consensus Guidelines on the Management of Community-Acquired Pneumonia in Adults, 2019
• Tintinalli's Emergency Medicine, 9th Edition