Pneumonia is a serious infection for everyone.  However, the elderly and immunocompromised such as those with AIDS or on chemotherapy have a much harder time recovering from pneumonia than healthy individuals.  Children often recover more quickly from pneumonia than the groups already mentioned.  However, some will go on to develop fluid or pus surrounding their lungs.  These patients become very ill and usually have to have the pus drained from the lung.  Also, it is often necessary to give these sicker patients oxygen because their lungs are not functioning well enough to keep the patient adequately oxygenated.  It is important that patients with fever and cough be evaluated and treated promptly to hopefully keep from developing a more serious pneumonia.