Using incidence rates and spatial analyses to identify areas for targeted interventions of La Crosse encephalitis in West Virginia, 2003 – 2007

In an effort to determine areas for targeted interventions by public health officials we calculated incidence rates and conducted spatial analyses at various geographic scales and using three population sets from La Crosse encephalitis case data gathered by the West Virginia Department of Health from 2003 -2007. We showed that incidence rates increased as geographic scales decreased – county to census tract level, and that using the population 15 years and under provided the best population sub-set to use for this disease. Using the sub-set population 15 years and under at the census tract level for those census tracts reporting cases we were able to determine incidence rates ranging from 42 – 506 per 100,000. Clustering of disease was detected at both the county and census tract levels using all population sets. Using both global and local spatial statistics we detected 4 clusters at the county level and 36 at the census tract level, for all population sets. Using smaller geographic scales for cluster detection will reduce the risk of missing focal clusters involving a small number of cases.