Pneumonia is an infection of one or both lungs which is usually caused by bacteria, viruses, or fungi. Pneumonia can range from mild to life life-threatening. Antibiotics can treat most forms of pneumonia. Bronchitis is a respiratory disease in which the mucous membrane in the lungs' bronchial passages becomes inflamed. It is a common condition, usually developing due to a cold or other respiratory infection. If you have repeated bouts of bronchitis it can be COPD and you should speak to your health care provider about treatment options.