I'r mwyafrif, salwch ysgafn fydd y ffliw. Serch hynny, i nifer fach sydd â chyflyrau meddygol arnynt eisoes, gall y symptomau fod yn fwy difrifol a gall y salwch arwain at gymhlethdodau.
For the majority, the flu is mild, however, for a small number with pre-existing medical conditions, the symptoms can be more severe and lead to  complications.