https://medicine.missouri.edu/news/researchers-identify-tech...
https://www.bmj.com/content/373/bmj.n1411/rr
https://www.rcpjournals.org/content/clinmedicine/21/1/e54
Some convalescent patients continue to test positive long after the infection is cleared and they are no longer contagious.
https://wi.mit.edu/news/new-research-reveals-why-some-patien...