Hayes (30), had been complaining to friends for more than a month about the virus which had left her feeling exhausted and nauseous and forced her to take time out from her daily lunchtime All Request Show on RTE 2fm.
However it wasn't until last weekend that doctors diagnosed the nature of the virus.
"Happy now I know what the five-week virus was. Just need someone to move in take me out of hospital and mind me," Hayes, from Baltinglass in Co Wicklow, told friends on her Facebook page last Saturday.
Hayes -- real name Eimear O'Keefe -- also revealed on her Bebo page that she has shed about a stone. The exact nature of Nikki's virus has not been revealed, nor has it been announced when she will return to work.
In 2008, she was off-air for five weeks following an attack by a male assailant in a Temple Bar hotel.