When I started work many years ago (back when dinosaurs roamed the earth), once you had taken more than 2 consecutive working days off sick, you needed a doctors sick note.
Sometime around 1980, this was extended to 5 days � many people incorrectly take this to be 7 days, because to those of us working a normal 5 day week (Sat & Sun off), this translates to 7 days. But if you happen to be doing a job that requires you to work 6 straight days, then on the 6th day, you will need a sick note.
Others may be able to confirm what I say to be correct.