Could mass testing for Covid-19 do more harm than good?

Making a diagnosis used to be a well understood and practised procedure: take a history from someone presenting with symptoms, examine them and do some tests to arrive at an overall diagnosis. It requires substantial training and experience to put this into practice. William Osler, known as one of the founders of modern medicine, often directed his trainees to ‘listen to the patient, he/she is telling you the diagnosis’.