Question: Talking about seeing an impact of holiday gatherings on community transmission, how does the US track home-testing results?

Answer: Short answer is that the US does not track the results of self-testing.  In its Self-Testing Guidance update of November 4th, 2021, CDC removed its recommendation to report all self-test results to healthcare providers or health departments, recommending instead that individuals reach out to their health care provider in the event of a positive or inconclusive test result.  Meanwhile, to inform contact tracing efforts and community transmission surveillance, some localities, like DC, ask residents to report their self-test results to their local health department.  Finally, because COVID-19 is a nationally notifiable disease, healthcare providers should include in their routine case notification through the National Notifiable Diseases Surveillance System any patient who reports a positive COVID self-test result.  This means that if a person with a positive self-test result reaches out to their health care provider, their case should be captured in local/state/national data.  Many health care providers will likely ask for a follow-up lab-based test to confirm the positive home-based test result, but I don’t know to what degree that happens.  When it does happen, those test results become part of local/state/national tracking data.