Yorkshire players Matthew Fisher, Tom Kohler-Cadmore, Josh Poysden and David Willey will miss their remaining T20 Blast group matches after one of them tested positive for coronavirus.
The club has not revealed which player has contracted the illness, but all four will isolate for the next 14 days.
They will miss Wednesday’s match with Durham and games with Lancashire on Thursday and Derbyshire on Sunday.
The quartet had already missed Monday’s six-wicket defeat by Lancashire.
BBC Radio Humberside understands that all four were in close contact on Saturday, separate to the squad and away from a Covid-secure environment.
Yorkshire are fourth in their T20 Blast group and could still reach the knockout stages.