Zika Virus in Ontario: Evaluating a Rapid Risk Assessment Tool for Emerging Infectious Disease Threats

To determine the Ontario-specific risk of local and travel-related Zika virus transmission in the context of a public health emergency of international concern, Public Health Ontario (PHO) completed a rapid risk assessment (RRA) on January 29, 2016, using a newly developed RRA guidance tool. The RRA concluded that risk of local mosquito-borne transmission was low, with a high risk of imported cases through travel. The RRA was updated 3 times based on predetermined triggers. An independent evaluation assessed both the application of the RRA guidance tool (process evaluation) and the usefulness of the RRA (outcome evaluation). We conducted face-to-face, semi-structured interviews with 7 individuals who participated in the creation or review of the Zika virus RRA and 4 end-users at PHO and the Ministry of Health and Long-Term Care. An inductive thematic analysis of responses was undertaken, whereby themes were directly informed by the data. The process evaluation determined that most steps outlined in the RRA guidance tool were adhered to, including forming a cross-functional writing team, clarifying the scope and describing context, completing the RRA summary report, and updating the RRA based on predefined triggers. The outcome evaluation found that end-users judged the Zika virus RRA as evidence-informed, useful, consistent, and timely. The evaluation established that the locally tailored guidance tool, adapted from national and international approaches to RRAs, facilitated a systematic, evidence-informed, and timely formal RRA process at PHO for the Zika virus RRA, which met the needs of end-users. Based on the evaluation, PHO will modify future RRAs by incorporating some flexibility into the literature review process to support timeliness of the RRA, explicitly describing the limitations of studies used to inform the RRA, and refining risk algorithms to better suit emerging infectious disease threats. It is anticipated that these refinements will improve upon the timely assessment of novel or reemerging infectious diseases.