Transmission dynamics and control of COVID-19 in Chile, March-June, 2020

Since the detection of first case of COVID-19 in Chile on March 3 ^rd , 2020, a total of 301019 cases including 6434 deaths have been reported in Chile as of July 7 ^th , 2020. In this manuscript we estimate the reproduction number during the early transmission phase in Chile and study the effectiveness of control interventions by conducting short-term forecasts based on the early transmission dynamics of COVID-19. We also estimate the reproduction number and conduct short term forecasts for the most recent developments in the epidemic trajectory of COVID-19 in Chile (May 9 ^th -July 7 ^th , 2020) to study the effectiveness of re-imposition of lockdowns in the country. The incidence curve in Chile displays early sub-exponential growth dynamics with the scaling of growth parameter, p , estimated at 0.8 (95% CI: 0.7, 0.8) and the reproduction number, estimated at 1.8 (95% CI: 1.6, 1.9). Our analysis emphasizes that the control measures at the start of the epidemic significantly slowed down the spread of the virus. However, easing of the COVID-19 restrictions and spread of virus to the low income neighborhoods in May led to a new wave of infections, followed by the re-imposition of lockdowns in Santiago and other municipalities. These measures have decelerated the virus spread with R estimated at ~0.87(95% CI: 0.84, 0.89) as of July 7 ^th , 2020. Our current findings point that the sustained transmission of SARS-CoV-2 in Chile is being brought under control. The COVID-19 epidemic followed an early sub-exponential growth trend ( p ~0.8) that transformed into a linear growth trend ( p ~0.5) as of July 7 ^th , 2020. While the broad scale social distancing interventions have slowed the virus spread, the number of new COVID-19 cases continue to accrue, underscoring the need for persistent social distancing and active case detection and isolation efforts to bring epidemic under control.