This study is to evaluate of the accuracy of biomarkers (i.e. circulating endothelial and immune activation markers) that indicate progression to severe disease in patients with suspected COVID-19 in the Emergency Department. It is a prospective observational study of patients presenting to emergency departments with a clinical suspicion of COVID19. All participants will have plasma samples collected for biomarker analysis, and will be tested for SARS-CoV-2 infection with a nasopharyngeal swab. Participants will be managed according to the best local practices.

Inclusion Criteria:

• Patients presenting with clinical suspicion of COVID-19 infection, as per UHN case definition at the time of presentation
• Age >18 years
• Ability to provide verbal informed consent

Exclusion Criteria:

• Patients who are not suspected of COVID-19 infection, as per UHN definition at the time of presentation

This study aims to enroll patients 18 years or older, presenting to Emergency Rooms or COVID-19 Assessment Centers with clinical suspicion of COVID-19 infection.