Cluster analysis
A cluster analysis was done using a regression tree analysis (Salford Predictive Modeler®, Version 8.2, Salford Systems, San Diego, California, USA). The median overall weighted score (median OWSDri ) being a continuous variable, the aim was to obtain groups of drivers with minimal within-group variance, with comparable likelihood to play a role in the emergence of COVID-19 in pets (e.g. very high importance, high importance, moderate importance and low importance). In addition, the statistical difference between medians after grouping drivers in clusters was assessed using a non-parametric Kruskal-Wallis equality-of-populations rank test. Indeed, each driver is characterised by a median (based on all experts’ answers), then drivers are grouped. The test allows highlighting potential significant differences between groups, in terms of driver medians, after clustering.