In an age of science, why are face masks a matter of opinion?

In 1846 Vienna, as across much of the world, a relatively new disease called puerperal (or ‘childbed’) fever had reached epidemic proportions in the local maternity hospital. Death rates of mothers and babies after childbirth were averaging 10 per cent, sometimes twice that. Across the western world millions were dying, the rate reaching 40 per cent in some hospitals. A Hungarian doctor in Vienna’s hospital, Dr Ignaz Semmelweis, began to wonder whether the problem might be something on the hands of doctors who’d been conducting post mortem examinations on the fever’s victims. He suggested handwashing with a chlorine solution. It worked. Deaths plummeted.

But Vienna’s medical community would have none of it, content with the well-established belief in foul winds as spreaders of disease: ‘miasma’ theory. Acceptance of ‘germ’ theory was some way off — and nor did Semmelweis quite reach it himself. He simply observed that handwashing worked. The medical authorities closed windows to keep ‘bad air’ out, and they treated Semmelweis the same way. True to form, then as now, the Viennese equivalent of the British Medical Association, outraged at any suggestion that their profession could be part of any problem, made him an outcast. Sacked, ridiculed and shunned, Semmelweis died later in a mental asylum.

The Hungarian doctor had believed in experiment and data collection. He’d worked on two maternity wards, one staffed by midwives and one by doctors. Deaths on the doctors’ ward exceeded those on the midwives’ side by a factor of five. Conditions were otherwise the same.

Why the disparity? Ignoring ingrained beliefs, Semmelweis had started physical trials, changing one condition at a time: birth position, for instance, even the priest’s bell. But a pathologist’s death from puerperal fever had given him a helpful posthumous nudge towards the autopsy room, so he’d tried a new variation, this time using the midwives (uninvolved in autopsies) as his control.