Causes and Risk Factors
Pneumonia develops when germs get past the body's defenses and infect the lungs:- Bacteria: Streptococcus pneumoniae (pneumococcus) is the most common bacterial cause in adults; "atypical" bacteria such as Mycoplasma cause a milder walking pneumonia.
- Viruses: Influenza, COVID-19, RSV, and other respiratory viruses can cause pneumonia directly or open the door to a bacterial infection.
- Aspiration: Food, liquid, or stomach contents inhaled into the lungs can trigger infection, especially in people with swallowing problems.
- Higher-risk groups: Risk rises with age over 65, smoking, and chronic conditions such as COPD, asthma, bronchiectasis, diabetes, heart disease, and weakened immunity.
Symptoms
- Cough: Often producing yellow, green, or rust-colored phlegm.
- Fever, chills, and sweats: Sometimes with shaking chills; older adults may instead have confusion or a low body temperature.
- Shortness of breath: With everyday activity or even at rest.
- Chest pain: Sharp pain that worsens with deep breathing or coughing.
- Fatigue and poor appetite: Weakness can linger for weeks after treatment.
Diagnosis
Your doctor listens for crackles in the lungs and typically confirms the diagnosis with a chest X-ray. Pulse oximetry checks oxygen levels, and blood tests or sputum cultures may identify the germ; rapid swabs can detect influenza and COVID-19 when a virus is suspected. Severity scoring based on age, vital signs, and lab results helps decide whether treatment at home is safe or hospital care is needed — most otherwise-healthy adults can be treated at home.Treatment
- Antibiotics: Bacterial pneumonia is treated with oral antibiotics such as amoxicillin-clavulanate, azithromycin, or doxycycline, chosen based on age, health conditions, and local resistance patterns; respiratory fluoroquinolones such as levofloxacin are reserved for selected patients. Most people improve within a few days of starting treatment.
- Supportive care: Rest, fluids, and fever reducers help recovery; viral pneumonia may also be treated with antivirals when appropriate.
- Hospital care: Needed when oxygen levels are low, blood pressure drops, or the infection is severe.