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Participation in symptom surveillance and SARS-CoV-2 serology and virology testing over time. Blue bars represent number of negative serology results. Yellow bars represent number of positive serology results. Gray bars represent number of negative virology results. Red bars represent number of positive virology results. The solid brown line represents number of daily symptom surveys completed. Abbreviation: SARS-CoV-2, severe acute respiratory syndrome coronavirus 2.
