Chasing the ghost of infection past: identifying thresholds of change during the COVID-19 infection in Spain

Luis Santamaria; Joaquin Hortal

The copyright holder for this preprint . https: //doi.org/10.1101 //doi.org/10. /2020 (2) A second phase, 1-2 weeks later, showing a highly consistent pattern of decreases in the growth rates of both the number of cases and the number of fatalities (49-65% and 40-56% reductions, respectively) at both geographical extents (Spain and Madrid). This inflection point, detected in the four variables analyzed, corresponds to infections taking place in the first week of March, following the issuing of preventive isolation measures (blue points 3-4 in Figure 5 ) and the increased awareness of the public opinion (as the perception of the increases in cases and deaths described in phase 1 emerged), but preceding the issuing of most social-distancing measures by the central and regional governments (blue points 5-7 in Figure 5 ). Owing to the lag times mentioned above, these decreases become perceivable between March 13-14 (for the number of cases) and March 26-27 (for the number of deaths). The perception of slowdown at March 13-14 was reinforced by the impact of the breaking points in the number of deaths detected during phase 1 (for infections taking place after February 23)underscoring the decoupling of cause and perception (see below).