Pneumonia is a serious respiratory infection that can be caused by bacteria, viruses, or other microorganisms. It is a severe infection of the lungs that causes inflammation and fluid buildup in the lung tissue. Pneumonia can be treated with antibiotics, but it can lead to serious complications if left untreated. If you are experiencing symptoms such as fever, cough, chest pain, shortness of breath, or difficulty breathing, it is important to see a pulmonologist for an evaluation and diagnosis.