A significant challenge in this SARS-CoV-2 (COVID-19) epidemic is properly allocating limited medical resources to the overwhelming numbers of patients presenting with symptoms. Even after a positive test for the COVID-19 virus, it is difficult to quickly and accurately predict whether a patient will suffer a severe course of illness and require hospitalization, or a mild course, and be safely cared for at home.This determination is particularly challenging with patients older than 60 or those with underlying diseases. Our previous studies on the SARS-CoV outbreak in 2002-2003, and on the influenza pandemic in 2009, demonstrated that biomarkers and leukocyte gene expression could be used for differentiating between mild and severe SARS at the molecular level. This current initiative will undertake retrospective and prospective biomarker studies on COVID-19 patients in Canada, China, the United States and in Spain, as well as in low and middle income countries using a 60-biomarker platform along with RNA sequencing and single cell sequencing of COVID-19 patients. By identifying and quantifying such biomarkers in relation to the progress and severity of COVID-19 illness, we will develop and contribute to rapid and reliable patient assessment tools, protocols and Point of Care Devices, which utilize biomarkers identified in this work. Further to this, the prospective nature of the study along with RNAseq and single cell sequencing will provide a clear picture of host immunity over the course of COVID-19 illness in mild, severe and critical outcome patients. Lastly, this research will identify correlates of protection in trials of candidate SARS-CoV-2 vaccines. These concepts will be implemented in partnership with the Nova Scotia Health Authority along with other jurisdictions across Canada and around the world as described in the following section.