Bayesian network analysis of Covid-19 data reveals higher infection prevalence rates and lower fatality rates than widely reported

Widely reported statistics on Covid-19 across the globe fail to take account of both the uncertainty of the data and possible explanations for this uncertainty. In this article, we use a Bayesian Network (BN) model to estimate the Covid-19 infection prevalence rate (IPR) and infection fatality rate (IFR) for different countries and regions, where relevant data are available. This combines multiple sources of data in a single model. The results show that Chelsea Mass. USA and Gangelt Germany have relatively higher IPRs than Santa Clara USA, Kobe, Japan, and England and Wales. In all cases the infection prevalence is significantly higher than what has been widely reported, with much higher community infection rates in all locations. For Santa Clara and Chelsea, both in the USA, the most likely IFR values are 0.3-0.4%. Kobe, Japan is very unusual in comparison with the others with values an order of magnitude less than the others at, 0.001%. The IFR for Spain is centred around 1%. England and Wales lie between Spain and the USA/German values with an IFR around 0.8%. There remains some uncertainty around these estimates but an IFR greater than 1% looks remote for all regions/countries. We use a Bayesian technique called 'virtual evidence' to test the sensitivity of the IFR to two significant sources of uncertainty: survey quality and uncertainty about Covid-19 death counts. In response the adjusted estimates for IFR are most likely to be in the range 0.3-0.5%.