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BACKGROUND: Legionnaire’s Disease (LD), a bacterial infection caused by Legionella species, is an important cause of pneumonia and hospitalization. LD is a reportable condition in Illinois, meaning that mandated reporters must report cases to the local health department within seven days. Surveillance of LD is captured by the Illinois National Electronic Disease Surveillance System (I-NEDSS), a web-based application that can be accessed by local health departments, healthcare providers, and laboratories throughout Illinois. The purpose of this surveillance system evaluation was to ensure that LD is being monitored efficiently and effectively in the state of Illinois. This evaluation involved an assessment of system attributes and includes recommendations for improving system quality, efficiency, and usefulness.
METHODS: This evaluation was modeled after the framework provided in CDC’s Updated Guidelines for Evaluating Public Health Surveillance Systems. I-NEDSS data from 2004 to 2013 were used to describe LD cases in Illinois and to assess surveillance system attributes. Local health departments were interviewed to identify attributes and characteristics that could be improved. Data quality was assessed by examining the completeness of surveillance records. System timeliness was evaluated by examining the time between disease onset, diagnosis date, and report date. To assess representativeness, the number of LD cases in I-NEDSS was compared to the number of cases in surrounding states.
RESULTS: Surveillance of LD in Illinois proved to be highly useful. The flexibility, acceptability, representativeness, and stability of the system were satisfactory, but the simplicity, data quality, and timeliness could be improved. From 2004 to 2013, 1,431 cases of LD were reported using the I-NEDSS system. Cases in Illinois increased considerably in 2012 and 2013, which was consistent with trends in surrounding states. Approximately 12% of cases were reported greater than seven days after the diagnosis date. Approximately 94% of cases submitted a urine specimen for laboratory testing.
CONCLUSIONS: Restructuring the surveillance module to include a list of potential exposures could improve the simplicity and data quality of the system. Local health departments should be encouraged to complete all fields of the surveillance module so that surveillance data can be useful for later analysis and investigation. Healthcare providers should be encouraged to order culture testing in addition to urinary antigen testing in order to compare human and environmental isolates and improve outbreak detection. Mandated reporters should be encouraged to report LD cases as soon as possible to improve the timeliness of the system.