As the COVID-19 epidemic spreads around the globe, countries rely on non-pharmaceutical interventions to slow the outbreak. An overarching aim is to flatten the epidemic curve so as to not exceed health care capacity limits. Inherent to this strategy is the assumption that with increasing mitigation strength the peak of the epidemic curve continuously decreases. We show that in any setting, where intervention measures include suspect testing and contact tracing, this assumption is incorrect and the process is discontinuous. This discontinuity is linked to a super-exponential growth phase and it considerably raises the stakes in epidemic control: The decisiveness of mitigation measures is not merely a question of 'flattening the curve' anymore but it sets the dividing line between effective suppression and a catastrophic outbreak .
High impact epidemics constitute one of the largest threats humanity is facing in the 21st century. Testing, contact tracing and quarantining are critical in slowing down epidemic dynamics, but may prove insufficient for highly contagious diseases. In the absence of pharmaceutical interventions, physical distancing measures remain as the last resort to avoid a widespread outbreak. Here we show that such combined countermeasures drastically change the rules of the epidemic transition if testing capacities are limited: Instead of continuous the response to countermeasures becomes discontinuous and rather than following the conventional exponential growth, the outbreak accelerates and scales super-exponentially during an intermediate period. As a consequence, containment measures either suffice to stop the outbreak at low total case numbers or fail catastrophically if marginally too weak, thus implying large uncertainties in reliably estimating overall epidemic dynamics, both during initial phases and during second wave scenarios .
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As the COVID-19 epidemic spreads around the globe, countries rely on non-pharmaceutical interventions to slow the outbreak. An overarching aim is to flatten the epidemic curve so as to not exceed health care capacity limits. Inherent to this strategy is the assumption that with increasing mitigation strength the peak
High impact epidemics constitute one of the largest threats humanity is facing in the 21st century. Testing, contact tracing and quarantining are critical in slowing down epidemic dynamics, but may prove insufficient for highly contagious diseases. In the absence of pharmaceutical interventions, physical distancing measures remain as the last resort to avoid a widespread outbreak. Here we show that such combined countermeasures drastically change the rules
R
curve continuously decreases. We show that in any setting, where intervention measures include suspect testing and contact tracing, this assumption is incorrect and the process is discontinuous. This discontinuity is linked to a super-exponential growth phase and it considerably raises the stakes in epidemic control: The decisiveness of mitigation measures is not merely a question of 'flattening the curve' anymore but it sets the dividing line between effective suppression and a catastrophic outbreak
transition if testing capacities are limited: Instead of continuous the response to countermeasures becomes discontinuous and rather than following the conventional exponential growth, the outbreak accelerates and scales super-exponentially during an intermediate period. As a consequence, containment measures either suffice to stop the outbreak at low total case numbers or fail catastrophically if marginally too weak, thus implying large uncertainties in reliably estimating overall epidemic dynamics, both during initial phases and during second wave scenarios