The "Big Brother All-Stars" are one step closer to becoming house guests once again ... they're in quarantine and their reality TV fates hinge on COVID-19 testing.
Production sources for season 22 tell TMZ ... a number of potential contestants arrived Tuesday in Los Angeles, where they're being sequestered and tested for the novel coronavirus as they await clearance to enter the 'Big Brother' house.
We're told the quarantine and testing process will take 2 weeks, and contestants will need a negative test before being allowed inside the house.
Our sources say 'BB' has a core list of returning contestants and an alternate list, just in case All-Stars from the core cast are forced to drop out due to a positive coronavirus test.
Here's who we know is quarantining in Hollywood so far ... season 19 winner Josh Martinez, season 8 runner-up Daniele Donato, season 18 alum Paulie Calafiore, season 18 winner Nicole Franzel, season 20 runner-up Tyler Crispen, three-time contestant Janelle Pierzina, season 14 winner Ian Terry, season 12 winner Hayden Moss and season 20 alum Bayleigh Dayton.