[Ed. – In other words, the infections were not spread by the candidates or their handling teams, who arrived the day of the debate. The final sentence, emphasis added, is the key.]
Officials for the City of Cleveland said 11 cases of the Wuhan coronavirus could be traced back to the Sept. 29 presidential debate. The cases were a result of debate pre-planning and set-up, with the majority of cases impacting out-of-state travelers, particularly debate organizers and members of the media. …
“As the cases involve people in and out of state some of whom may be continuing to travel, the City of Cleveland is working with the Ohio Department of Health (ODH), the Centers for Disease Control & Prevention and the Cleveland Clinic,” the city said in a statement.
[T]he Cleveland Clinic made one thing clear: every single person with credentials who went into the debate had to have a negative Wuhan coronavirus test.