Standard measures such as quarantining suspects and contact tracing could not contain the ongoing COVID-19 pandemic. Unlike for other recent epidemics where such instruments were successful, in the present case a large fraction of the infected have only mild unspecific symptoms. By employing network models we here show that even for near perfect contact tracing and unlimited suspect testing , containment starts to fail when more than approximately half of the carriers fall into the weak-symptom category. The situation becomes considerably more severe if the number of daily available tests is limited. In this case the epidemic transition becomes discontinuous and a much larger percentage of the population becomes infected. While moderate levels of social distancing can bring the situation back under control, the limited number of daily tests introduces a finite time horizon: If social distancing is implemented after the cut off date, containment catastrophically breaks down resulting in an exponential disease spread .
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 .
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Standard measures such as quarantining suspects and contact tracing could not contain the ongoing
As the
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pandemic. Unlike for other recent epidemics where such instruments were successful, in the present case a large fraction of the infected have only mild unspecific symptoms. By employing network models we here show that even for near perfect contact tracing and unlimited suspect testing , containment starts to fail when more than approximately half of the carriers fall into the weak-symptom category. The situation becomes considerably more severe if the number of daily available tests is limited. In this case the epidemic transition becomes discontinuous and a much larger percentage of the population becomes infected. While moderate levels of social distancing can bring the situation back under control, the limited number of daily tests introduces a finite time horizon: If social distancing is implemented after the cut off date, containment catastrophically breaks down resulting in an exponential disease spread
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