An observable finding or state that persists over time and tends to require intervention or management, and, therefore, distinguished from an Observation made at a point in time; may exist before an Observation of the Condition is made or after interventions to manage the Condition are undertaken. Examples: equipment repair status, device recall status, a health risk, a financial risk, public health risk, pregnancy, health maintenance, chronic illness

A public health case is an Observation representing a condition or event that has a specific significance for public health. Typically it involves an instance or instances of a reportable infectious disease or other condition. The public health case can include a health-related event concerning a single individual or it may refer to multiple health-related events that are occurrences of the same disease or condition of interest to public health. An outbreak involving multiple individuals may be considered as a type of public health case. A public health case definition (Act.moodCode = "definition") includes the description of the clinical, laboratory, and epidemiologic indicators associated with a disease or condition of interest to public health. There are case definitions for conditions that are reportable, as well as for those that are not. There are also case definitions for outbreaks. A public health case definition is a construct used by public health for the purpose of counting cases, and should not be used as clinical indications for treatment. Examples include AIDS, toxic-shock syndrome, and salmonellosis and their associated indicators that are used to define a case.

An outbreak represents a series of public health cases. The date on which an outbreak starts is the earliest date of onset among the cases assigned to the outbreak, and its ending date is the last date of onset among the cases assigned to the outbreak.