Christ Tshiunza has tested positive for Covid-19.
The Wales back-row has been forced into isolation after returning a positive test on Monday - making him an immediate doubt for Wales' tournament opener against Ireland.
A Welsh Rugby Union statement read: "After returning a positive lateral flow test on Monday’s entry screening, he immediately went into isolation.
"A subsequent PCR test taken on Monday confirmed the result. He will now isolate as per government guidelines."
Having made his debut last autumn, the Exeter forward, who can also play in the second-row, would have been in contention to feature against Ireland in Dublin on February 5, given Wales' lack of destructive options on the blindside.
However, given his relative lack of senior minutes at both club and international level, the blow of isolation denies him the chance to lay down a pre-tournament marker in training.
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