A single holiday was the turning point of the COVID-19 policy of Israel

Klausner, Ziv; Fattal, Eyal; Hirsch, Eitan; Shapira, Shmuel C.

OBJECTIVES: Despite an initial success, Israel’s quarantine-isolation COVID-19 policy has collapsed abruptly. This study’s aim is to identify the causes that lead to this exponential rise in the accumulation of confirmed cases. METHODS: Epidemiological investigation reports were used to reconstruct chains of transmission as well as assess the net contribution of local infections relative to imported cases, infected travelers arriving from abroad. A mathematical model was implemented in order to describe the efficiency of the quarantine-isolation policy and the inflow of imported cases. The model simulations included two scenarios for the actual time series of the symptomatic cases, providing insights regarding the conditions that lead to the abrupt change. RESULTS: The abrupt change followed the Jewish holiday of Purim in which many public gatherings were held. According to the first scenario, the accumulation of confirmed cases before Purim was driven by imported cases resulting in controlled regime, with an effective reproduction number, [Formula: see text] , of 0.69. In the second scenario which followed Purim, a continuous rise of the local to imported cases ratio began, which led to an exponential growth regime characterized by [Formula: see text] of 4.34. It was found that the change of regime cannot be attributed to super-spreader events, as these consisted of approximately 5% of the primary cases which resulted in 17% of the secondary cases. CONCLUSIONS: A general lesson for health policy makers should be that even a short lapse in public responsiveness can lead to dire consequences.