Nosophobia is the irrational fear of having a specific disease. It is related to hypochondriasis, but there are several important differences between the two conditions. The most important difference is specificity.
A person with hypochondriasis has several physical symptoms that he or she fears may be caused by illness. Someone with nosophobia, however, is afraid of a specific disease and becomes convinced that he or she has the symptoms of that particular disease.
Nosophobia appears to be more common among students and researchers who spend a great deal of time reading about specific diseases. These conditions are often called "medical student’s disease" and "cyberchondria," respectively.