fox news medical contributor joining us in a few moments on what this means. talk to us about this so-called rebound infection. first let s go to david live on the north lawn at the white house. hi. clearly not something we expected today. i don t think anyone expected this. he was going to go to wilmington delaware tomorrow. the white house announced the trip to michigan on tuesday. both of those events have been canceled. delaware and michigan because of this rebound positivity test. we have a letter from the president position, he says after testing negative on tuesday evening, wednesday morning, thursday morning and friday morning, the president tested positive saturday morning by antigen testing. this represents rebound positivity. the president has expensed no reemergence of symptoms and continues to feel quite well. there was no reason to reinstate treatment at this time. we will continue close observation. the president tweeting out to his millions of followers, i