Both America's Harris English and South African Dylan Frittelli have withdrawn from the £6 million event as the Covid-19 issue looms ever more ominous for the circuit that resumed three weeks ago.
English, 30, hoins Nick Watney, Cameron Champ, Denny McCarthy and Dylan Frittelli in testing positive for the coronavirus since the PGA Tour resumed following a three-month hiatus created to mitigate the pandemic's spread on June 11.
"While it's disappointing to receive this news, as I feel healthy, I'm pleased that the new safety protocols we have in place worked this week", said the American.
"I am looking forward to competing again once it is deemed safe for me to make my return", said Campbell.
The two-time PGA Tour victor received the diagnosis after undergoing a screening ahead of this week's Rocket Mortgage Classic.
After conducting contact tracing, the tour said its medical advisors are not recommending additional testing at this time.
Cameron Champ and Denny McCarthy, who hit an opening round of 67, withdrew from the event following positive results, while Graeme McDowell and Brooks Koepka did not participate after their respective caddies returned positive tests.
Frittelli missed the cut in CT last Friday but failed the test when arriving to board the Tour's charter to fly from CT to MI.
English, a 30-year-old from Georgia ranked 139th in the world, won his only two PGA titles in 2013 at the St. Jude Classic and Mayakoba Classic.
Campbell withdrew from this week's Rocket Mortgage Classic in Detroit, Michigan, where he was slated to be a first alternate, and said he would quarantine himself until he has made a full recovery.