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.