Illustration of a moderate stenosis (narrowing) of the aortic valve caused by rheumatic fever. The merging of a commissure (left, centre) can be seen as well as the beginning of the merger of the other flaps. This prevents the outflow of blood from the ventricle into the aorta. Rheumatic fever is a disease that can develop after a bacterial infection, causing painful joints and heart problems. It can affect the heart, joints, brain and skin. Some symptoms of rheumatic fever include a high temperature, breathlessness and a fast heart rate.