England number eight Alex Dombrandt is a doubt for Saturday's Six Nations meeting with Ireland after testing positive for Covid.

Meanwhile, flanker Sam Underhill returns to the 36-man squad before next weekend's match at Twickenham.

But scrum-half Raffi Quirke (concussion) and lock Jonny Hill (foot) have both been ruled out.

Alex Mitchell comes into the squad instead of Quirke, with hooker Nic Dolly also called up after the injury to Luke Cowan-Dickie.

While Dombrandt no longer needs to legally isolate after his positive test, under the RFU's own guidelines he will not be able to return to training until the middle of next week at the earliest.

According to an RFU spokesperson, he will "be assessed and tested daily and brought back in when considered safe for him and rest of squad."

With the Harlequins forward testing positive last Friday, he is not expected to be able to train until at least Wednesday, and will need to return a negative result to do so.

Elsewhere, flanker Tom Curry, who was concussed against Wales, has been named in the squad but it is understood he has not yet passed his Return To Play protocols.

As expected, centre Manu Tuilagi will not feature after a hamstring setback and is unlikely to play again this Championship, with Hill definitely ruled out after being sent back to his club Exeter.

Head coach Eddie Jones has though seen his options in the back row aided by the inclusion of Underhill who made his return from concussion in Bath's thrilling late win against Bristol at the weekend.

After an opening-day defeat away at Scotland, England kept their title hopes intact with wins over Italy and Wales, but now face the two stiffest challenges of the tournament over the coming fortnight, with Ireland this weekend followed by unbeaten France in Paris on the final day.

"Ireland are a great team and their attack is sharp at the moment," scrum-half Harry Randall told BBC Sport.

"Their breakdown is good and they play with quick ball.

"It's going to be a big game. We treated Wales like our quarter-final, and this is our semi-final.

"We are definitely at the business end."