Inclusion Criteria:  To participate in this Study, individuals must:  Have access to an iPhone 6s or later with compatible iOS as defined by the Apple App Store. Have regular and reliable internet access Be willing to comply with all Study procedures, including regular use of the Apple Watch (daytime and nighttime), complete the REDCap and Apple Research app surveys, share data from required Apple Watch and iPhone sensors, and perform self-collected nasal swabs Be able to read and comprehend English Be able to provide informed consent without the use of a legally authorized representative Have a permanent mailing address in the greater Seattle area where Study materials can be mailed Be at least 22 years old at the time of consent  Exclusion Criteria:  To participate in this Study, individuals must not:  Have previously tested positive for SARS-CoV-2 via PCR or antibody test Currently be enrolled in University of Washington Husky Coronavirus Testing, Household Observation Study, or any other Seattle Flu Study sub-Study Have received any vaccine for COVID-19 or have an upcoming appointment for at least one dose of any COVID-19 vaccine prior to Study consent  Individuals also may be excluded from the Study once target participant counts have been achieved for certain demographics, comorbidity groups, and/or residence based on zip code