Originally Posted by FEasy

Well, it's not a tracing exercise at this stage. You keep a record and it is encoded by secretarial staff every day. So there is some control and social pressure to comply. Also, it's unlikely someone will start lying in advance of getting sick. But of course there may be errors and omissions. A watertight system would be way, way more burdensome - if at all possible - for a very marginal gain in risk reduction compared to what they put in place now (which, frankly, is already creating quite some overhead).