[1] Symptom onset is defined as the date on which symptoms first began, including non-respiratory symptoms.[2] PCR testing is defined as the use of an RT-PCR assay to detect the presence of SARS-CoV-2 RNA..: From Wölfel et al., demonstrating declining viral burden in upper respiratory specimens as illness progresses and decreasing capacity to isolate replication-competent virus from these same specimens as the number of patients with detectable IgM and IgG increases.: From Midgley et al., demonstrating inability to recover replication-competent virus from specimens collected more than 9 days after illness onset.