The unknown player has been quarantined since Friday morning after suffering from a fever.
A spokesperson for the team told reporters that the player had only been to minor-league camp, did not visit the major-league complex, and had no contact with any players or staff who've been on the major-league side, according to Erik Boland of Newsday.
The Yankees' minor-league complex has been closed for the past two days, as was the original plan, according to Kristie Ackert of The New York Daily News.
The Yankees plan to test at least some other minor leaguers for the virus, according to Jon Heyman of MLB Network.
The team's minor leaguers will also be quarantined for the next two weeks with food being delivered to their hotel rooms, sources told Ken Rosenthal and Lindsey Adler of The Athletic.