Impact of contact tracing, respect of isolation and lockdown in reducing the number of cases infected with COVID-19: Case study: Tunisia’s response from March 22 to 04 May 2020

Saidi, Olfa; Malouche, Dhafer; Saksena, Priyanka; Arfaoui, Latifa; Talmoudi, Khouloud; Hchaichi, Aicha; Bouguerra, Hend; Romdhane, Habiba Ben; Hsairi, Mohamed; Ouhichi, Ramzi; Souteyrand, Yves; Alaya, Nissaf Ben

Background COVID-19 has grown rapidly across the world. Tunisia reacted early to COVID-19 resulting in low number of infections. In this paper we model the effects of different interventions on the evolution of cases and compare this to the Tunisian experience. Methods We use a stochastic transmission model to quantify the reduction in number of cases of COVID-19 of interventions of contact tracing, compliance with isolation and a general lockdown. Results Increasing contact tracing from 20% to 80% after the first 100 cases reduces the cumulative number of infections (CNI) by 52% in one month. Similarly, increased compliance to isolation from 20% to 80% after the first 100 cases reduces the CNI by 45%. These reductions are smaller if the interventions are implemented after 1000 cases. A general lockdown reduces the CNI by 97% after the first 100 cases. Tunisia implemented its general lockdown after 75 cases were confirmed, reduced the cumulative number of infected cases by 86% among the general population. Conclusions This study shows that early application of critical interventions contributes to significantly reducing infections and the evolution of COVID-19 in a country. Tunisia’s early success with control of COVID-19 is explained by its quick response.