England have added centre Jonathan Joseph to their Six Nations training squad while captain Owen Farrell has been included despite concerns over his fitness.
Johnny Sexton has joined Ireland's Six Nations training squad in Portugal while France forward Bernard Le Roux has been ruled out of the tournament with a knee injury.
Ireland forward Tadhg Beirne will miss the opening two matches of the Six Nations due to a knee injury, Irish Rugby Football Union confirmed on Monday.
Scotland have included four new players into their Six Nations squad but flanker Hamish Wilson has withdrawn due to a hand injury.
Flanker Brad Shields has become the latest injury concern for England ahead of the Six Nations after he was ruled out of Wasps' European Champions Cup clash with Leinster.
Dylan Hartley has been left out of England's Six Nations squad due to injury as Eddie Jones included four uncapped players in his 35-man group.