When President Trump makes his appearance on Thursday night on NBC News, he is expected to speak, probably maskless, with the moderator, Savannah Guthrie, and the audience sitting at least 12 feet away. But he is unlikely to transmit the coronavirus to any of those people, multiple experts said.
Since Mr. Trump first announced his diagnosis this month, questions about his infectiousness have swirled because it is still unclear exactly when and how he became ill or how severe his symptoms have been.
“From a safety standpoint, and a public health standpoint, I think it’s probably fine, although we don’t have all the information that I would like to have in order to make that call,” said Dr. Rochelle Walensky, an infectious disease physician at Massachusetts General Hospital in Boston.
Mr. Trump announced his positive test in the early hours of Oct. 2, and was given several powerful treatments in rapid succession, including monoclonal antibodies to give his immune system a boost and a steroid that prevents dangerous inflammation.
The Centers for Disease Control and Prevention recommends that infected patients isolate for at least 10 days if they had mild or moderate illness, and for up to 20 days if they had severe symptoms. The steroid Mr. Trump received, dexamethasone, can also prolong the duration of infectiousness.
But without information about Mr. Trump’s oxygen levels or scans of his lungs, it’s impossible to know how severe his illness has been, doctors said. Based only on the information available, “it sounds like ultimately, he had mild to moderate disease,” Dr. Walensky said.
After a hospitalization of four days, Mr. Trump has recuperated mostly at the White House, but he has appeared at several public events, including a rally on Tuesday in Johnstown, Pa.
The chief White House physician, Dr. Sean P. Conley, has sometimes provided cryptic reports on the president’s recovery. On Monday, for example, Dr. Conley said that Mr. Trump had tested negative multiple times on the Abbott BinaxNOW test, which is not intended to confirm the absence of the virus. The doctor also alluded to other results not provided by any commercial test.
But on Tuesday, at the insistence of NBC News, the White House provided Mr. Trump’s result from a P.C.R. test — the gold standard lab diagnostic for the coronavirus — to Dr. Anthony S. Fauci, the country’s top infectious disease expert, and Dr. Clifford Lane, a clinical director at the National Institutes of Health.
Mr. Trump’s P.C.R. test had a cycle threshold, or surrogate for viral load, of 34.3, Dr. Fauci has said. According to data provided by the C.D.C., people with a threshold over 33 carry little to no live virus. Dr. Fauci and Dr. Lane also looked at results from attempts to grow live virus from Mr. Trump’s samples.
After reviewing the data, they cleared Mr. Trump to attend the town hall event. “We feel confident that we can say with a high degree of confidence that he is not transmissible,” Dr. Fauci said in an interview on Wednesday.
Other experts agreed with that assessment. “We actually have multiple bits of data that suggest that the president is not infectious, and that it would be safe for him to go and participate in the town hall,” said Dr. Daniel Griffin, an infectious disease physician at Columbia University.
Still, some experts questioned Mr. Trump’s decision to hold a live event so soon after his illness.
“It’s also about the appearance of what it means when a rich and powerful person can have access to all these technologies to potentially break out of public health isolation,” said Dr. Nahid Bhadelia, medical director of the Special Pathogens Unit at Boston Medical Center.
Even if Mr. Trump is unlikely to transmit the virus to others, NBC News should act with extreme caution, she said, adding, “The onus now falls on the organizers of the town hall to ensure that there is a level of public health mitigation — efforts put into place like wearing masks, keeping physical distance, ensuring good ventilation in the room.”