Table 1 Surveillance attributes considered in the analysis

Acceptability

The willingness of persons and organizations to participate in the surveillance system.

Cost-effectiveness

Relationship between the expected outcomes (such as the number of lives saved) and the costs of surveillance required to achieve this. May be expressed as a measure of efficiency, whereby the system operates at the least possible cost or makes the best use of available resources.

Data quality

Completeness and validity of the data recorded.

Flexibility

Ability to adapt to changing information needs or operating conditions with little additional time, personnel or allocated funds. Flexible systems can accommodate new health-related events, changes in case definitions or technology, and variations in funding or reporting sources.

Positive predictive value

The proportion of reported cases that actually have the infection/condition of interest.

Representativeness

The extent to which features of the population of interest (e.g. herd size, age, location) are reflected in the surveillance data that are collected.

Sensitivity

For endemic diseases, sensitivity refers to the proportion of cases of a disease detected by the surveillance system (this usually requires a gold standard test to indicate the actual number of cases). For non-endemic diseases, sensitivity refers to the ability of a surveillance system to detect disease outbreaks.

Simplicity

Refers to the surveillance system structure, ease of operation and flow of data through the system.

Stability

Reliability (function without failure) and availability (operational when needed)

Timeliness

Speed between steps in a surveillance system. For outbreak detection, timeliness refers to the time between exposure to the infectious agent and the initiation of interventions to control infection.