Measuring Time-Varying Effective Reproduction Numbers for COVID-19 and Their Relationship with Movement Control Order in Malaysia

Abstract

To curb the spread of SARS-CoV-2 virus (COVID-19) in Malaysia, the government imposed a nationwide movement control order (MCO) from 18 March 2020 to 3 May 2020. It was enforced in four phases (i.e., MCO 1, MCO 2, MCO 3 and MCO 4). In this paper, we propose an initiative to assess the impact of MCO by using time-varying reproduction number (<i>Rt</i>). We used data from the Johns Hopkins University Centre for Systems Science and Engineering Coronavirus repository. Day 1 was taken from the first assumed local transmission of COVID-19. We estimated <i>Rt</i> by using the <b>EpiEstim</b> package and plotted the epidemic curve and <i>Rt</i>. Then, we extracted the mean <i>Rt</i> at day 1, day 5 and day 10 for all MCO phases and compared the differences. The <i>Rt</i> values peaked around day 43, which was shortly before the start of MCO 1. The means for <i>Rt</i> at day 1, day 5, and day 10 for all MCOs ranged between 0.665 and 1.147. The average <i>Rt</i> gradually decreased in MCO 1 and MCO 2. Although spikes in the number of confirmed cases were observed when restrictions were gradually relaxed in the later MCO phases, the situation remained under control with <i>Rt</i> values being stabilised to below unity level (<i>Rt</i> value less than one).