Multi-site disease analytics with applications to estimating COVID-19 undetected cases in Canada

Even with daily case counts, the true scope of the COVID-19 pandemic in Canada is unknown due to undetected cases. We estimate the pandemic scope through a new multi-site model using publicly available disease count data including detected cases, recoveries among detected cases, and total deaths. These counts are used to estimate the case detection probability, the infection fatality rate through time, as well as the probability of recovery, and several important population parameters including the rate of spread, and importation of external cases. We also estimate the total number of active COVID-19 cases per region of Canada for each reporting interval. We applied this multi-site model Canada-wide to all provinces and territories, providing an estimate of the total COVID-19 burden for the 90 weeks from 23 Apr 2020 to 6 Jan 2022. We also applied this model to the five Health Authority regions of British Columbia, Canada, describing the pandemic in B.C. over the 31 weeks from 2 Apr 2020 to 30 Oct 2020.