Batsman Nick Selman has tested positive for coronavirus following the results of a PCR test.
He will now spend 10 days in self-isolation.
The club also identified Marnus Labuschagne and Michael Neser as potential close contacts and are taking the precautionary measure of removing them from the match day squad.
All other team members, coaches and staff returned negative results and the fixture against Middlesex today will go ahead as planned with batsman Billy Root and Sam Pearce brought in to the squad.
23-year-old Pearce is a leg-spinning all-rounder and a product of the Glamorgan Academy. He is the current captain of Wales National County and a member of the Cardiff UCCE side that won the BUCS National Cricket Championship earlier this week.
Glamorgan squad to face Middlesex: Chris Cooke *+, Colin Ingram, David Lloyd, Kiran Carlson, Billy Root, Callum Taylor, Dan Douthwaite, James Weighell, Timm van der Gugten, Prem Sisodiya, Roman Walker, Tom Cullen, Sam Pearce.