Technical description of RODS: a real-time public health surveillance system

Abstract

This report describes the design and implementation of the Real-time Outbreak and Disease Surveillance (RODS) system, a computer-based public health surveillance system for early detection of disease outbreaks. Hospitals send RODS data from clinical encounters over virtual private networks and leased lines using the Health Level 7 (HL7) message protocol. The data are sent in real time. RODS automatically classifies the registration chief complaint from the visit into one of seven syndrome categories using Bayesian classifiers. It stores the data in a relational database, aggregates the data for analysis using data warehousing techniques, applies univariate and multivariate statistical detection algorithms to the data, and alerts users of when the algorithms identify anomalous patterns in the syndrome counts. RODS also has a Web-based user interface that supports temporal and spatial analyses. RODS processes sales of over-the-counter health care products in a similar manner but receives such data in batch mode on a daily basis. RODS was used during the 2002 Winter Olympics and currently operates in two states-Pennsylvania and Utah. It has been and continues to be a resource for implementing, evaluating, and applying new methods of public health surveillance.

Figure 1.

Data communication to RODS system from various health systems. (HSRC, health system resident component; VPN, virtual private network).

Figure 2.

Sample HL7 admission, discharge, and transfer (ADT) message from an emergency department. The circled fields are age, gender, home zip code, admitted date and time, and free-text chief complaint, respectively.

Figure 3.

Health care registrations view in the Main screen of RODS. The Main screen alternates views every 2 minutes among data types available in the public health jurisdiction. The figure shows eight plots of health care registration data—total visits, botulinic, constitutional, gastrointestinal (GI), hemorrhagic, neurological, rash, and respiratory. After 2 minutes, over-the-counter data will be displayed. The Main screen can be used as a “situation room” display.

Figure 4.

Epiplot screen of RODS. The six graphs are user-selected time-series plots of emergency department visits and sales of over-the-counter (OTC) products in Pennsylvania—OTC all categories, OTC cough/cold, OTC thermometers, clinic total visits, clinic constitutional, and clinic respiratory—between January 1, 2003, and February 1, 2003. Users can view a mixture of different syndromes and OTC product categories for any geographic region (state, county, or zip code), and for any time interval. Users can select types of data from the pick-list on the left of the screen. The Download data button retrieves raw count data for the selected graphs to a compressed comma-separated file. The Get Cases button shows a list of records containing chief complaint, age in decile, gender, and patient home zip code within the specified time interval and the geographic region. The lower, red line in the OTC plots represents nonpromoted sales.

Figure 5.

Mapplot screen of RODS shows spatial distribution of respiratory cases in part of Utah. Olympic venues are labeled.

Figure 6.

Look-back function of RODS. The user has selected one patient to investigate using the screen that is in the background and partly hidden by overlap. RODS has logged the user into the results-review function of an electronic medical record and requested that patient's chart, which is shown on the screen in the foreground.