Welsh international Jamie Roberts has tested positive for coronavirus, days before the season is due to restart.
Earlier this month, Roberts signed for the Dragons, who are due to face the Ospreys on Sunday.
The experienced centre is in good health but is now self-isolating and will not feature this weekend.
The rest of the Dragons squad have been re-tested this week and if there are more cases in their ranks, this weekend's game will be in doubt.
On Tuesday night, the region put out a statement saying: "Dragons Rugby has returned a positive case for COVID-19 in Welsh Rugby’s testing programme in the round of tests taken week commencing Monday, August 10.
"All subsequent Public Health Wales and Government guidelines are being followed and the individual – who is symptom free and in good health – is currently isolating.
"Dragons Rugby is part of the wider Welsh Rugby Union screening programme which has conducted over 1,100 tests to date as part of the return to training/ playing process.
"This is a confidential and private health matter and we will make no further comment."
