Wikipedia has more on Nosophobia
Nosophobia is the fear of becoming ill.
This phobia is sometimes caused by a negative experience with illness, such as a loved one dying from a fatal disease. If a person is genetically predisposed to a disease that killed their loved one, they are even more likely to become nosophobic. Gruesome portrayals of illness in TV and movies may also cause one to develop the phobia.
Those who suffer from nosophobia constantly worry about falling ill. They may try to prevent themselves from getting sick by eating food and/or taking vitamins to strengthen their immune system, such as those that contain Vitamin C. They may also avoid germs and wash their hands frequently, in a similar manner to a germophobe. If they believe that they may be ill, they may show signs of a panic attack, such as trembling, nausea, and shortness of breath. These signs resemble symptoms of real illnesses, causing them to panic even more in a vicious cycle.
Nosophobia is often comorbid with hypochondriasis and/or obsessive-compulsive disorder (OCD).