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’. 

With Covid-19, however, clinical diagnosis is seemingly a secondary consideration in the face of mass testing. All you require is a positive PCR test; no symptoms, no signs, no other diagnostic proof. But our limited understanding of mass testing and PCR suggests this might not suffice.

Detection of viruses using Polymerase Chain Reaction (PCR) is helpful so long as its accuracy can be understood: it offers the capacity to detect RNA in minute quantities, but whether that RNA represents infectious virus is another matter. RT-PCR