In an interview on Wednesday, Dr. Fauci said that he and Dr. Lane had reviewed the P.C.R. result, as well as data from viral cultures and multiple negative tests on a rapid antigen test, Abbott’s BinaxNOW.
Dr. Fauci said he and Dr. Lane had corresponded with Dr. Conley, who provided all of the information that they assessed. “We were just given the data and we made a determination from the data,” Dr. Fauci said.
Combined with the fact that Mr. Trump was more than 10 days out from the onset of symptoms, Dr. Fauci said, “We can say with a high degree of confidence that he is not transmissible.”
Mr. Trump’s P.C.R. test had a cycle threshold — a proxy for viral load — of 34.3, Dr. Fauci said. According to data provided by the Centers for Disease Control and Prevention, people with a threshold over 33 carry little to no live virus.
The NBC town hall will be held outdoors at the Pérez Art Museum in Miami, and audience members will be required to wear face masks. The network said that Ms. Guthrie and Mr. Trump would be seated at least 12 feet apart.
Dr. Conley, the White House physician, has not taken reporters’ questions in more than a week. On Monday, he said that Mr. Trump had tested negative “on consecutive days” using a rapid antigen coronavirus test not intended for that purpose. Experts have cautioned that the test’s accuracy has not yet been investigated enough to be sure that the president is virus-free.
The NBC event is one of Mr. Trump’s last opportunities of the campaign to make his case before a large televised audience. It will be simulcast on MSNBC and CNBC, virtually guaranteeing the president a higher Nielsen rating than Mr. Biden’s town hall that night, which is set to air on a single traditional TV network. (Nielsen ratings do not encompass many online streaming views.)
The two candidates are also scheduled to meet for a final debate in Nashville next Thursday, Oct. 22, moderated by the NBC News correspondent Kristen Welker.
Maggie Haberman contributed reporting.