Periodic clinical evaluation of an individual who is at increased risk of developing a condition (compared with the general population) aimed at detecting new or recurrent disease. In public health, surveillance may also refer to the systematic collection of information regarding the incidence, prevalence, and mortality related to various medical conditions or health-related events. or In medicine, closely watching a patient’s condition but not treating it unless there are changes in test results. Surveillance is also used to find early signs that a disease has come back. It may also be used for a person who has an increased risk of a disease, such as cancer. During surveillance, certain exams and tests are done on a regular schedule. In public health, surveillance may also refer to the ongoing collection of information about a disease, such as cancer, in a certain group of people. The information collected may include where the disease occurs in a population and whether it affects people of a certain gender, age, or ethnic group.