Of The Data Layer

An evaluator can study an entire system, a subsystem, or a component of a biosurveillance system. The following example is a pilot study conducted by Tsui et al. (2005) of the "data-layer" (subsystem) of a biosurveillance system. This subsystem encompassed computers located in hospitals, the Internet, and computers in a biosurveillance facility that received and stored the data.

This study compared the time latency, reliability, data loss, implementation cost, and effort for two subsystems that collected surveillance data from hospitals: one using direct connections to hospital HL7 message routers and the other batch transfer of files. The evaluators studied direct (54) and batch (2) data feeds from 56 hospitals in Pennsylvania and Utah to the RODS Public Health Data Center (PHDC). The data being transmitted were registration records containing patient chief complaints.

They measured time latency as the delay between patient registration and receipt of registration information by the PHDC; reliability, as the number of investigations of malfunctioning data feeds per connection-month; and data loss

table 37-2 Characteristics of Real-Time and Batch Feeds


Real Time


Median time latency (hours)

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