The Sun newspaper reports that former Love Island star Curtis had shown no symptoms of coronavirus and had self-isolated for two weeks before he began working on Celebs Go Dating, but confirmed he had returned a positive test.
It comes just weeks after his older brother AJ, 28, tested positive for COVID-19.
Watch: How will the new tiers system be reviewed?
The former Strictly Come Dancing professional dancer’s appearance on I’m A Celebrity was cast into doubt when he tested positive for coronavirus, but after quarantining for two weeks ahead of filming he was allowed to take part.
It was revealed this week that AJ and Curtis’s grandmother has died, aged 93. Known to the family as Nanna, she had been diagnosed with dementia 10 years previously, and passed away in hospital.
The Pritchard family have made the decision not to tell AJ while he is still in the ITV reality show, which is filming at a castle in north Wales and is due to end on Friday.
Curtis revealed on social media: “It is following our grandad's wishes that myself and AJ are to carry on with the current projects we are committed to.
"Grandad said to myself and AJ that it would break his heart for us to stop what we were doing as Nanna had such pride in our work.
“AJ therefore discussed with the family before entering the castle that if something did happen to Nanna whilst he was away, that he wouldn't want to be told until he left the castle and that in her honour he would complete his commitment to the show, with a view to doing her and the family proud.
"As Grandad and Nanna would have wished for, AJ will stay in the castle and continue making her proud wherever she is watching from."
As Curtis had already begun filming Celebs Go Dating on location at a mansion in Surrey, the show has now been put on hold, and all the other celebrity contestants - including CBBC presenter and actor Karim Zeroual, Gary Lineker’s brother Wayne Lineker, Geordie Shore’s Chloe Ferry and Made In Chelsea star Sophie Hermann - must now self-isolate until everyone has tested negative.
A spokeswoman for Lime Pictures said: "The cast member who tested positive earlier for COVID during filming Celebs Go Dating has since tested negative on subsequent occasions.
"Having taken extensive medical advice and with the support of Public Health England they are deemed to be non-infective.
"All cast members will be tested prior to entering the house following their recent isolation. Celebs Go Dating filming will resume imminently."
Watch: AJ Pritchard clash with Shane Richie on I’m A Celeb