It's not a set number for the US either, we have Family Medical Leave (FMLA). When they say you have sick days it's referring to paid sick leave by your job. If you're sick you can be out for sick leave for quite a long time and the jobs can't do anything against you, they just don't have to pay you. If you're so sick that you're on FMLA for a long time you'll probably qualify for Short Term Disability which you might also supplement with Short Term disability insurance.