Estimation of the basic reproduction number (R0) for the novel coronavirus disease in Sri Lanka
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RESEARCH
Estimation of the basic reproduction number (R0) for the novel coronavirus disease in Sri Lanka Samath Dharmaratne1,2, Supun Sudaraka1, Ishanya Abeyagunawardena1* , Kasun Manchanayake3, Mahen Kothalawala4 and Wasantha Gunathunga5
Abstract Background: The basic reproduction number (R0) is the number of cases directly caused by an infected individual throughout his infectious period. R0 is used to determine the ability of a disease to spread within a given population. The reproduction number (R) represents the transmissibility of a disease. Objectives: We aimed to calculate the R0 of Coronavirus disease-2019 (COVID-19) in Sri Lanka and to describe the variation of R, with its implications to the prevention and control of the disease. Methods: Data was obtained from daily situation reports of the Epidemiology Unit, Sri Lanka and a compartmental model was used to calculate the R0 using estimated model parameters.This value was corroborated by using two more methods, the exponential growth rate method and maximum likelihood method to obtain a better estimate for R0. The variation of R was illustrated using a Bayesian statistical inference-based method. Results: The R0 calculated by the first model was 1.02 [confidence interval (CI) of 0.75–1.29] with a root mean squared error of 7.72. The exponential growth rate method and the maximum likelihood estimation method yielded an R0 of 0.93 (CI of 0.77–1.10) and a R0 of 1.23 (CI of 0.94–1.57) respectively. The variation of R ranged from 0.69 to 2.20. Conclusion: The estimated R0 for COVID-19 in Sri Lanka, calculated by three different methods, falls between 0.93 and 1.23, and the transmissibility R has reduced, indicating that measures implemented have achieved a good control of disease. Keywords: Basic reproduction number, R0, Coronavirus Introduction Sri Lanka reported its first patient with the novel Coronavirus disease-2019 (COVID-19) on the January 27th, 2020, a Chinese female visiting the country [1]. The first local patient was reported on March 11th, 2020 thus bringing about unprecedented changes in the daily life in the country [2]. Rigorous measures were implemented
*Correspondence: [email protected] 1 Faculty of Medicine, University of Peradeniya, Kandy, Sri Lanka Full list of author information is available at the end of the article
to reduce the spread of the disease, however despite these measures new patients were reported almost every day [3–7]. The rise in the daily total number of patients did not however show a marked exponential rise but remained steady after the first week [3]. This pattern lasted up to April 19th, 2020 following which, the detection of two clusters of patients led to a sudden increase in the number of cases [8, 9]. However, since then due to government interventions including meticulous testing, the numbers have once again started to reduce [3]. In this paper, we aimed to calculate the R0 for the spread of COVID-19 in Sri Lanka and to describe the variation of R
© The Author(s) 2020. This article is l
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