What causes pneumonia?

Inflammation can fill air sacs with fluid and make it harder for oxygen to move into the blood. Pneumonia may follow a respiratory infection or develop when germs reach the lungs in another way. COVID-19 and Influenza are viral illnesses that can cause pneumonia in some people.

Bacterial pneumonia can occur after a viral illness or begin on its own. Fungal causes are less common and depend on immune health and exposure. Inhaled saliva, food, or stomach contents can also irritate or infect the lungs. Age, chronic lung or heart disease, smoking, and a weakened immune system can increase vulnerability without being the direct cause.

Contact a clinician for a new cough with fever, chest discomfort, breathlessness, marked tiredness, or confusion. Assessment may include listening to the chest, checking oxygen levels, and arranging imaging or other tests. Treatment is selected according to the likely cause; antibiotics do not treat viral infections.

Rest, drink fluids if you can do so safely, avoid smoking, and follow the prescribed treatment. Do not use leftover antibiotics, and seek review if symptoms worsen or fail to improve as expected.

Seek emergency care for severe breathlessness, blue or grey lips, new confusion, fainting, severe chest pain, or inability to stay awake. Prompt assessment is also needed when a person with pneumonia is becoming weaker, cannot keep fluids down, or has worsening breathing after initial treatment.

Ask whether the pattern suggests a bacterial, viral, fungal, or aspiration cause; whether you need a chest scan or oxygen check; which treatment to take; and which breathing changes require emergency help.