Mertz is awaiting a PCR swab test to confirm the initial positive diagnosis.
The Kansas native will have to sit out practice and games for 21 days if the results are confirmed, according to Big Ten protocols, adds Bartholomew. The signal-caller will also undergo comprehensive cardiac testing if the initial findings hold up.
Mertz is coming off the heels of a breakout performance - he completed a school-record 17 consecutive passes and 20 of 21 pass attempts for 248 yards with five touchdowns in a rout of Illinois.
The reported positive test comes nearly a week after Purdue head coach Jeff Brohm's announcement about contracting the virus.
Wisconsin is 1-0 on the season and is scheduled to play on the road against Nebraska on Oct. 31.