Classification of pneumonia

Pneumonia is an inflammatory condition of the lung primarily affecting the small air sacs known as alveoli. Typically, symptoms include some combination of productive or dry cough, chest pain, fever, and trouble breathing. Severity is variable. Pneumonia is usually caused by infection with viruses or bacteria and less commonly by other microorganisms, certain medications, or conditions such as autoimmune diseases.

Classification

Pneumonia can be classified in several ways, most commonly by where it was acquired (community, hospital, or health care associated), by the causative organism, and by the area of lung affected.

By Acquisition

• Community-Acquired Pneumonia (CAP): This is the most common type of pneumonia. It occurs outside of hospitals or other health care facilities. It is commonly caused by bacteria, with Streptococcus pneumoniae being the most common.
• Hospital-Acquired Pneumonia (HAP): This type of pneumonia occurs 48 hours or more after admission to a hospital and was not present at the time of admission. It is often more serious because the bacteria involved may be more resistant to antibiotics.
• Ventilator-Associated Pneumonia (VAP): A subset of HAP, this occurs in people who are on mechanical ventilation through an endotracheal or tracheostomy tube.
• Healthcare-Associated Pneumonia (HCAP): This type occurs in people who have been in other health care facilities, like nursing homes or dialysis centers, within the last 90 days.

By Causative Organism

• Bacterial Pneumonia: Caused by bacteria, the most common being Streptococcus pneumoniae. Other bacteria include Haemophilus influenzae and Legionella pneumophila.
• Viral Pneumonia: Caused by various viruses, including influenza, respiratory syncytial virus (RSV), and SARS-CoV-2, the virus responsible for COVID-19.
• Fungal Pneumonia: More common in individuals with weakened immune systems, fungal pneumonia can be caused by organisms such as Pneumocystis jirovecii, Cryptococcus neoformans, and Histoplasma capsulatum.

By Area of Lung Affected

• Lobar Pneumonia: Involves a specific lobe or lobes of the lung.
• Bronchopneumonia: Affects patches throughout both lungs.

Diagnosis

Diagnosis of pneumonia often involves a combination of physical signs, chest X-rays, and a person's sputum being tested with culture or antigen detection tests. Blood tests and CT scans are also sometimes used to diagnose pneumonia or to determine the severity of the disease.

Treatment

Treatment depends on the underlying cause of pneumonia. Bacterial pneumonia is treated with antibiotics. Viral pneumonia may require antiviral medication, though in many cases, treatment is supportive. Fungal pneumonia is treated with antifungal agents.

Prevention

Preventative measures include vaccination, appropriate hand hygiene, and smoking cessation. Vaccines are available for some causes of bacterial and viral pneumonia.

Prognosis

The prognosis for pneumonia varies widely depending on the type of pneumonia, the treatment received, and the patient's underlying health conditions. While most people recover from pneumonia, it can be life-threatening, particularly for the elderly, infants, and those with weakened immune systems or chronic diseases.