If you get a positive test, you're cleared to return to your life after 14 days of the test, or 10 days after the onset of symptoms. A negative tests is not required to "come off" of quarantine or isolation. Just the passage of days. So at least since mid summer, there should be very few repeat positive tests. In fact, some people can test positive for months after...but are not infections and not expected to isolate. That doesn't answer your question, other than my gut feeling that there just aren't many/any? such cases in the "current" data set...