![[ Visit Client Website ]](images/banner.jpg)
BACKGROUND: In the 14-year period from 1993 to 2006, New York State (NYS) accounted for over one-quarter (27.1%) of all confirmed Lyme disease (LD) cases in the United States. During that time period, a nine-county area in southeast NYS reported 90.6% of the LD cases in the state. Based on concern voiced by local health department (LHD) staff in this area regarding the burden of traditional LD surveillance, the NYS Department of Health (DOH) sought to develop an alternative to traditional surveillance that would reduce the investigative workload while maintaining the ability to track LD trends. Thus, a surveillance system was developed and implemented in 2007 to estimate county-level LD cases based on a twenty-percent random sample of positive laboratory reports.
METHODS: A random number generator was used to generate and assign an investigative indicator to 20% of all laboratory reports reported to the NYSDOH. The records assigned the investigative indicator were forwarded to LHDs for investigation. Estimates were calculated by multiplying the number of confirmed and probable cases resulting from LHD investigation of laboratory reports by five and adding cases with no associated laboratory report (primarily physician-reported erythema migrans cases). The estimates were compared to the number of cases using the traditional surveillance methodology in nine instances over the seven-year period that sampling estimation has been conducted. The representativeness of demographic and symptom variables were also examined.
RESULTS: Four counties with high LD investigative burden agreed to conduct sampling estimation in 2007. The number of counties (outside of New York City) using the sampling methodology grew to 19 (33.3%) by 2013. Significant differences between actual and estimated case counts were found in three of the nine evaluations conducted. Few (5.1%) significant differences were found when comparing proportions of demographic and symptom variables for the sampling estimation versus traditional surveillance.
CONCLUSIONS: Overall, sampling estimation was efficient and accurate in estimating LD cases at the county level and reduced investigative burden. Use of case estimates for LD should be considered as a useful surveillance alternative by health decision makers in states with endemic LD.