Dal colera del 1854 al Covid-19

John Snow.s method of limiting contagion and death in the 1854 cholera epidemic is one of the foundations of modern epidemiology: a fine example of how data, statistical information and knowledge can make an essential contribution. Yet today, in the course of the COVID-19 pandemic, what Snow did cannot be done. I refer to the Italian case (although some points can be easily generalised) to identify some obstacles and propose possible solutions: we do not know where the infected live and where they have become infected; we do not know their demographic and socio-economic characteristics; we do not have sufficient information on mobility; we do not make full use of the conceptual tools we have; the principle of privacy overrides the principle of public health. In the conclusions, I offer an example of what could be done if these obstacles were removed. In particular, I refer to a recent paper to illustrate the contribution that statistics and mathematical models could make to inform public opinion and to provide authorities with suggestions for more effective and equitable pandemic policies.