Former US vice president and Democratic presidential nominee Joe Biden needs to be tested for Covid-19 after having been on the same stage as President Donald Trump on Tuesday night, said CNN's Chief Medical Correspondent Dr. Sanjay Gupta.
"He does need to be immediately tested. He has come in proximity to someone that has Covid," Gupta said.
Trump has not revealed any symptoms yet, and a White House statement said he and first lady Melania Trump are "both well."
But "as you well know, going back to (top aide) Hope Hicks, you can be contagious or more contagious before you develop some of the symptoms -- the pre-symptomatic period," Gupta warned.
Biden and Trump both attended the first presidential debate on Tuesday night, though they stayed on different sides of the stage at their own podiums. Biden may have been standing far enough from Trump to avoid infection -- but "if you are indoors, you could think of the virus like smoke," Gupta said. It's not clear if the two men interacted backstage or behind cameras.