England head coach Andy Robinson revealed that Leicester back-row forward Moody was in hospital as the England squad set off for Dublin.
Moody has been put on a drip in an attempt to force antibiotics through his infected finger.
If the treatment is successful it is hoped he will join up with the rest of the squad on Friday.
But Robinson admitted: "The chances of him playing are very slim. The infection is deeper than was originally thought."
Moody suffered a cut to his finger during England's defeat by France at Twickenham a fortnight ago and the injury became infected during a 10-minute appearance as a replacement in Leicester's crushing 83-10 victory over Newcastle in the Premiership last weekend.
Robinson said: "The mud got into it. He has had quite a big course of antibiotics but they haven't done the job we hoped they would.
"He has now had to go into hospital and been put on a drip to force the antibiotics through,' added Robinson.