Pneumonia
An infection that inflames the air sacs in one or both lungs
Table of Contents
Overview
Pneumonia is an infection that inflames the air sacs (alveoli) in one or both lungs. The air sacs may fill with fluid or pus, causing cough with phlegm or pus, fever, chills, and difficulty breathing. Various organisms, including bacteria, viruses, and fungi, can cause pneumonia.
Pneumonia can range in seriousness from mild to life-threatening. It is most serious for infants and young children, people older than age 65, and people with health problems or weakened immune systems. Each year in the United States, about 1 million people are hospitalized with pneumonia, and about 50,000 people die from the disease.
The infection can be acquired in various settings, each with different implications for treatment. Community-acquired pneumonia is the most common type, occurring outside of hospitals or other healthcare facilities. Hospital-acquired pneumonia, which occurs during a hospital stay, can be more serious because the bacteria causing it may be more resistant to antibiotics and because the people who get it are already sick.
Types of Pneumonia
By Causative Agent
Bacterial Pneumonia
The most common cause of pneumonia in adults. Streptococcus pneumoniae (pneumococcus) is the most common bacterial cause. Other bacteria include Haemophilus influenzae, Mycoplasma pneumoniae, and Legionella pneumophila.
Viral Pneumonia
Common in children and can be caused by respiratory viruses including influenza, respiratory syncytial virus (RSV), and coronaviruses (including SARS-CoV-2 that causes COVID-19). Usually milder than bacterial pneumonia but can become serious.
Fungal Pneumonia
Most common in people with chronic health problems or weakened immune systems. Caused by fungi from soil or bird droppings. Examples include Pneumocystis jirovecii, Cryptococcus, and Histoplasma.
Aspiration Pneumonia
Occurs when food, drink, vomit, or saliva is breathed into the lungs. More likely if something disturbs your normal gag reflex, such as brain injury, swallowing problems, or excessive alcohol or drug use.
By Location Acquired
Community-Acquired Pneumonia (CAP)
The most common type, acquired outside of hospitals or healthcare facilities. Can be caused by bacteria, viruses, or fungi.
Hospital-Acquired Pneumonia (HAP)
Develops 48 hours or more after hospital admission. Often more serious due to antibiotic-resistant bacteria and patients' underlying conditions.
Healthcare-Associated Pneumonia (HCAP)
Occurs in people who have been in nursing homes, dialysis centers, or outpatient clinics. Similar organisms to HAP.
Ventilator-Associated Pneumonia (VAP)
Develops in people on mechanical ventilation. Has high mortality rates and often involves resistant organisms.
Symptoms
Pneumonia symptoms can vary from mild to severe, depending on factors such as the type of germ causing the infection, your age, and overall health:
Common Respiratory Symptoms
Systemic Symptoms
Upper Respiratory Symptoms
Age-Specific Symptoms
In Infants and Children
- Fast breathing or trouble breathing
- Grunting sounds when breathing
- Decreased appetite
- Irritability or restlessness
- Dehydration
In Older Adults
- Lower than normal body temperature
- Confusion or changes in mental awareness
- May have fewer or milder symptoms
- Sudden worsening of chronic conditions
Seek Emergency Care If:
- Difficulty breathing or shortness of breath
- Chest pain
- Confusion or changes in mental awareness
- Persistent fever above 102°F (39°C)
- Coughing up blood
- Bluish color to lips or fingernails
Causes and Risk Factors
Many germs can cause pneumonia. Understanding the causes and risk factors helps in prevention and treatment:
Common Causative Agents
Bacteria
- Streptococcus pneumoniae: Most common bacterial cause
- Haemophilus influenzae: Often in people with COPD
- Mycoplasma pneumoniae: Causes "walking pneumonia"
- Legionella pneumophila: From contaminated water systems
- Staphylococcus aureus: Including MRSA strains
- Klebsiella pneumoniae: Often in alcoholics and diabetics
Viruses
- Influenza viruses
- Respiratory syncytial virus (RSV)
- Coronaviruses (including SARS-CoV-2)
- Adenovirus
- Parainfluenza viruses
- Human metapneumovirus
Risk Factors
Age Groups at Higher Risk
- Children younger than 2 years
- Adults 65 years and older
Health Conditions
- Chronic diseases: COPD, asthma, heart disease, diabetes
- Weakened immune system: HIV/AIDS, cancer treatment, organ transplant
- Neurological conditions: That affect swallowing or coughing
- Recent respiratory infection: Cold or flu
- Malnutrition: Poor nutritional status
Lifestyle and Environmental Factors
- Smoking: Damages lung's natural defenses
- Alcohol abuse: Increases aspiration risk
- Hospitalization: Especially ICU or ventilator use
- Exposure to chemicals: Toxic fumes or pollutants
- Crowded living conditions: Nursing homes, prisons
Diagnosis
Diagnosing pneumonia involves a combination of medical history, physical examination, and diagnostic tests:
Initial Assessment
- Medical history: Symptoms, duration, risk factors, recent travel
- Physical examination: Listening to lungs with stethoscope for abnormal sounds
- Vital signs: Temperature, blood pressure, heart rate, oxygen saturation
Diagnostic Tests
Chest X-ray
Primary imaging test to confirm pneumonia diagnosis, showing location and extent of infection. May show infiltrates, consolidation, or fluid in lungs.
Blood Tests
- Complete blood count: Checks for elevated white blood cells
- Blood cultures: Identifies specific bacteria in bloodstream
- Arterial blood gas: Measures oxygen levels
- Inflammatory markers: C-reactive protein, procalcitonin
Sputum Tests
Analysis of mucus coughed up from lungs to identify causative organism and guide antibiotic selection.
CT Scan
More detailed than X-ray, used when diagnosis is unclear or to evaluate complications.
Pulse Oximetry
Non-invasive test measuring oxygen saturation in blood. Helps determine need for oxygen therapy.
Additional Tests
- Bronchoscopy: For severe cases or when diagnosis unclear
- Pleural fluid analysis: If fluid around lungs present
- Urine antigen tests: For specific bacteria like pneumococcus or Legionella
- PCR tests: For viral causes including COVID-19
Treatment
Treatment for pneumonia depends on the type and severity of pneumonia, age, and overall health status:
Antibiotic Treatment
Community-Acquired Pneumonia
- Outpatient: Macrolides (azithromycin) or doxycycline
- Outpatient with comorbidities: Fluoroquinolones or beta-lactam plus macrolide
- Inpatient: Beta-lactam plus macrolide or fluoroquinolone alone
- ICU: Beta-lactam plus either macrolide or fluoroquinolone
Hospital-Acquired Pneumonia
Requires broad-spectrum antibiotics covering resistant organisms. Often includes combinations like piperacillin-tazobactam, carbapenems, or cephalosporins with coverage for MRSA if needed.
Antiviral Treatment
Influenza Pneumonia
Oseltamivir (Tamiflu) or other neuraminidase inhibitors if started within 48 hours of symptom onset.
COVID-19 Pneumonia
Treatment may include antivirals, corticosteroids, and monoclonal antibodies depending on severity and patient factors.
Supportive Care
Oxygen Therapy
For patients with low oxygen levels. Can range from nasal cannula to mechanical ventilation in severe cases.
Fluid Management
IV fluids for dehydration, careful monitoring to avoid fluid overload.
Symptom Management
- Fever reducers (acetaminophen, ibuprofen)
- Cough suppressants (use cautiously)
- Bronchodilators for wheezing
- Pain management for pleuritic chest pain
Hospitalization Criteria
Factors indicating need for hospital admission:
- Confusion or altered mental status
- Low blood pressure
- Rapid breathing (>30 breaths/minute)
- Low oxygen saturation
- Multiple lobes affected on chest X-ray
- Inability to maintain oral intake
- Significant comorbidities
Recovery and Care
Recovery from pneumonia varies depending on severity, age, and overall health. Most people start feeling better within a few days of starting treatment:
Recovery Timeline
- 1-3 days: Fever should break with antibiotic treatment
- 1 week: Significant improvement in symptoms
- 2-4 weeks: Most symptoms resolved, but fatigue may persist
- 6-8 weeks: Full recovery for most people
- 3-6 months: Complete recovery for severe cases
Home Care Guidelines
- Rest: Get plenty of sleep and avoid overexertion
- Hydration: Drink plenty of fluids to help loosen secretions
- Medication compliance: Complete full course of antibiotics
- Breathing exercises: Deep breathing to prevent complications
- Humidified air: Use humidifier to ease breathing
- Avoid smoke: Stay away from cigarette smoke and pollutants
Follow-up Care
- Medical appointments: Usually within 2-3 days for severe cases
- Chest X-ray: May be repeated in 6-8 weeks to ensure clearing
- Monitoring: Watch for worsening symptoms or complications
- Gradual activity: Slowly increase activity as tolerated
When to Return to Doctor
- Fever returns after initial improvement
- Breathing becomes more difficult
- Chest pain worsens
- Coughing up blood
- No improvement after 2-3 days of antibiotics
- New confusion or dizziness
Prevention
Many cases of pneumonia can be prevented through vaccination and healthy lifestyle practices:
Vaccinations
Pneumococcal Vaccines
- PCV13 (Prevnar 13): For children under 2 and adults 65+
- PPSV23 (Pneumovax 23): For adults 65+ and younger people with risk factors
- PCV20 (Prevnar 20): Newer vaccine for adults
Annual Flu Vaccine
Prevents influenza, which can lead to viral pneumonia or secondary bacterial pneumonia.
COVID-19 Vaccine
Reduces risk of COVID-19 pneumonia and severe disease.
Other Vaccines
- Hib vaccine for children
- Pertussis vaccine
- Measles vaccine
- Varicella vaccine
Lifestyle Measures
- Hand hygiene: Wash hands frequently with soap and water
- Don't smoke: Smoking damages lung defenses
- Good health habits: Adequate sleep, healthy diet, regular exercise
- Avoid sick people: Limit exposure during cold and flu season
- Cover coughs: Use elbow or tissue, not hands
- Clean surfaces: Disinfect frequently touched surfaces
High-Risk Groups
People who should take extra precautions:
- Adults 65 years and older
- Children younger than 5 years
- People with chronic medical conditions
- Immunocompromised individuals
- Residents of long-term care facilities
- Smokers
Complications
While most people recover from pneumonia without lasting effects, serious complications can occur:
Respiratory Failure
Severe pneumonia can cause lungs to fail at providing enough oxygen to the blood, requiring mechanical ventilation.
Sepsis
Infection spreads to bloodstream causing body-wide inflammation. Can lead to septic shock and organ failure.
Lung Abscess
Pus-filled cavity in the lung that may require drainage or prolonged antibiotic therapy.
Pleural Effusion
Fluid accumulation between lung and chest wall. May require drainage if large or infected (empyema).
Acute Respiratory Distress Syndrome (ARDS)
Severe lung inflammation and fluid accumulation preventing adequate oxygen exchange.
Kidney Failure
Can occur due to severe infection, low blood pressure, or certain antibiotics.
Long-term Effects
- Reduced lung function
- Increased susceptibility to future infections
- Chronic fatigue
- Cognitive impairment in elderly
- Worsening of chronic conditions