Comments on 'some methodological issues in biosurveillance'.

We greatly appreciate the opportunity to comment on this interesting and thought-provoking paper. Dr Fricker has brought up many important issues with respect to biosurveillance, primarily in the very challenging context of syndromic surveillance and other types of public health surveillance with many input data streams. Similar to Dr Fricker, we have backgrounds in industrial statistical process control (SPC). Our study of public health surveillance and health-care monitoring issues began roughly 6 years ago. Some of what we learned was summarized in two review papers, Woodall [1] and Tsui et al. [2], aimed primarily toward industrial SPC researchers and practitioners. We have studied several public health surveillance topics, including sets methods [3], temporal scan approaches [4--6], and spatiotemporal methods [7--10] [Tsui et al. 2010; submitted]. Although there are no fundamental points of disagreement between Dr Fricker’s views and ours, we would like to elaborate on a few topics and share our experience with respect to industrial SPC methods and ideas and how they relate to public health surveillance.