Louis Lynagh has withdrawn from the England squad for Saturday's Six Nations meeting with Ireland after testing positive for Covid-19.
The Harlequins winger, 21, returned a positive test on Monday afternoon and immediately went into isolation.
The rest of England's players and staff have returned negative results.
Number eight Alex Dombrandt is also a doubt following a positive test as England prepare to host Ireland at Twickenham at 16:45 GMT on Saturday.
Dombrandt, who started the wins over Italy and Wales, returned his positive result last Friday and is not expected to be able to train until at least Wednesday.