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.
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