Rahm was leading the tournament after the third round with a 6-stroke cushion over his closest competitors.
The PGA Tour said Rahm was placed in contact tracing protocols on Monday after officials learned he had been in close contact with someone who was Covid-19 positive.
Rahm elected to remain in the tournament and undergo daily testing and have restricted access to indoor facilities at Muirfield Village Golf Club in Dublin, Ohio.
He remained asymptomatic and tested negative every day, the PGA Tour said. But a test performed after Rahm completed his rain-delayed second round on Saturday morning returned a positive result as did a confirmatory test on the original sample, according to the PGA Tour.
The Tour’s medical adviser informed Rahm of his test results upon completion of his third round and, following Tour protocols, he was withdrawn from the competition.
Rahm will remain in isolation for the next 10 days in accordance with CDC guidelines.
“While this is an incredibly unfortunate situation, throughout 50 events since the PGA TOUR’s Return to Golf, there have been only four positive tests (including Rahm) within competition,” the PGA Tour said in its statement. “Rahm is the first positive, asymptomatic case as part of the TOUR’s routine, contact-tracing protocols.”
In his Saturday statement, Rahm said he will take all the necessary precautions “to be safe and healthy” and looks forward to returning to the golf course as soon as possible.
“Thank you to all of the fans for their support and I’m looking forward to watching the showdown tomorrow afternoon with you all,” he added.
CNN’s Jacob Lev contributed to this report.