Evaluation of a West Nile virus risk-assessment tool used at a local health unit

Abstract

In Ontario, public health units collect surveillance data on vector-borne diseases (VBD) to determine emerging trends and develop VBD management strategies. Risk-assessment tools that are simple and easily applied can provide public health practitioners with objective evaluations of the risk of West Nile virus (WNV) activity in their jurisdiction. This study was conducted to evaluate an existing WNV risk-assessment tool used by a public health unit in southern Ontario. The purpose of this study was to: (i) describe the trends for WNV in mosquito and human cases in the Region of Peel, Ontario, Canada, and (ii) investigate the ability of the risk-assessment tool to predict positive human cases and positive mosquito traps in the following weeks. Data were collected from 2011 to 2016 and analysed using simple descriptive statistics and Fisher’s exact tests. This study found the tool includes variables that are not significant in predicting WNV activity in the following weeks. The current tool should be revised to remove variables that are not significant in predicting risk and add additional variables that have been shown to be effective predictors in other studies, such as rainfall and human WNV cases in the previous year.