Incidence is the number of new cases of a condition, symptom, death, or injury that develop during a specific time period, such as a year. The number is often expressed as a percentage of a population. For example, 25% of Americans were diagnosed with the flu in 2002.

Incidence shows the likelihood that a person in that population will be affected by the condition.

Review Date: 05/02/2009
Reviewed By: Linda J. Vorvick, MD, Medical Director, MEDEX Northwest Division of Physician Assistant Studies, University of Washington, School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org)