key: cord-332066-8mdg6172 authors: Thway, A. M.; Tayza, H.; Win, T. T.; Tun, Y. M.; Aung, M. M.; Win, Y. N.; Tun, K. M. title: Epidemiological characteristics of SARS-COV-2 in Myanmar date: 2020-08-04 journal: nan DOI: 10.1101/2020.08.02.20166504 sha: doc_id: 332066 cord_uid: 8mdg6172 Coronavirus disease (COVID-19) is an infectious disease caused by a newly discovered severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). In Myanmar, first COVID-19 reported cases were identified on 23rd March 2020. There were 336 reported confirmed cases, 261 recovered and 6 deaths through 13th July 2020. The study was a retrospective case series and all COVID-19 confirmed cases from 23rd March to 13th July 2020 were included. The data series of COVID-19 cases were extracted from the daily official reports of the Ministry of Health and Sports (MOHS), Myanmar and Centers for Disease Control and Prevention (CDC), Myanmar. Among 336 confirmed cases, there were 169 cases with reported transmission events. The median serial interval was 4 days (IQR 3, 2-5) with the range of 0 - 26 days. The mean of the reproduction number was 1.44 with (95% CI = 1.30-1.60) by exponential growth method and 1.32 with (95% CI = 0.98-1.73) confident interval by maximum likelihood method. This study outlined the epidemiological characteristics and epidemic parameters of COVID-19 in Myanmar. The estimation parameters in this study can be comparable with other studies and variability of these parameters can be considered when implementing disease control strategy in Myanmar. Coronavirus disease (COVID-19) is an infectious disease caused by a newly discovered severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). It was first identified as the cause of a cluster of pneumonia cases in Wuhan, a city in the Hubei Province of China at the end of 2019, and then it was rapidly spreading in China and other countries [1, 2] . Consequently, COVID-19 has become a major global health concern, and it was recognized as a pandemic by the World Health Organization (WHO) on 11 th March 2020 [3] . The daily total number of cases were steady rising with affecting 213 countries and territories around the world. Globally, there were more than 12 million (12,768,307) confirmed cases including 566,654 deaths through 13 th July 2020 [4] . United States of America, Brazil, India, Russia Federation and Peru were the most effected countries. Among WHO regions, America, Europe and Eastern Mediterranean Regions were highest affected regions. In South East Asia region, there were more than one million (1,163,556) confirmed cases and 31,297 case are deaths [4, 5] . SARS-CoV-2 can be spread by human-to-human transmission via droplets or direct contact [6] . The infection has been estimated to have mean incubation period of 6.4 days and a . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted August 4, 2020. . https://doi.org/10.1101/2020.08.02.20166504 doi: medRxiv preprint 3 mean basic reproduction number (R 0 ) was 3.38 with a range of 1.90 to 6.49 [7] [8] [9] . The incubation period for COVID-19 is on average 5-6 days, but it can be up to 14 days [10] . Moreover, as outliers, the patients with incubation period of 19 days [11] and 24 days [12] [18] . It was close to or shorter than its median incubation period, and a substantial proportion of secondary transmission might occur prior to illness onset [17] . Most people with COVID-19 would experience mild to moderate respiratory illness and recover without requiring special treatment. However, older people, and those with underlying medical problems such as cardiovascular disease, diabetes, chronic respiratory disease, and cancer were more likely to develop serious illness [1]. In Myanmar, first COVID-19 reported cases were identified on 23 rd March 2020. There were 336 reported confirmed cases, 261 recovered and 6 deaths through 13 th July 2020. Obviously, reported confirmed cases were gradually increased in Yangon Region, an epicenter of COVID-19 outbreak, and majority of cases (242 cases) were reported from this region [19] . The government of Myanmar has extended several restrictions including the suspension of international commercial flights, bans on public gatherings, and closures of public events, entertainment venues and religious institutions. Since 16 th May 2020, almost new cases were imported cases who returned back from other countries and they have already been in quarantine centres. Most cases were identified in people return back from foreign countries [20] . The COVID-19 pandemic has disrupted economic activities and is expected to have a long-term impact on various sectors. The critical importance are epidemiologic investigations to characterize mode of transmission, reproduction number, serial interval, and clinical spectrum of infection in order to reform and refine strategies that can stop the spread of COVID-19 [21] . The characterization of the epidemiological features of COVID-19 is also vital for the development and implementation of effective prevention and control measures. This study aimed to describe the epidemiology characteristics and main epidemiological parameters of COVID-19 in Myanmar. . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted August 4, 2020. . https://doi.org/10.1101/2020.08.02.20166504 doi: medRxiv preprint 4 The study was a retrospective case series and all COVID-19 confirmed cases from 23 rd March to 13 th July 2020 were included. The data series of COVID-19 cases were extracted from the daily official reports . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted August 4, 2020. . https://doi.org/10.1101/2020.08.02.20166504 doi: medRxiv preprint 5 The Epidemiological parameter included epidemic curve, basic reproduction number (R 0 ), serial interval and close contact of a confirmed case. An epidemic curve is a visual display of the onset of illness among cases associated with an outbreak. The general sense of the outbreak's magnitude and inferences about the outbreak's pattern of spread could be estimated [25] . R 0 was defined as the expected number of secondary cases that one primary case will generate in a susceptible population. If R 0 is above the critical threshold of 1, continuous humanto-human transmission with sustained transmission will occur [24] . R 0 package implements a simple, likelihood-based estimation of R 0 using a branching process with a Poisson likelihood. Infectiousness is determined by weighting R 0 by the probability mass function of the serial interval on the corresponding day. It is a simplified version of the model introduced by Jombart T et al. in 2013 [26] . Reproduction numbers may be calculated by different method. The exponential method and maximum likelihood method were used to estimate the reproduction numbers in this study. The serial interval of COVID 19 is defined as the time elapsed between a primary casepatient (infector) having symptom onset and a secondary case-patient (infectee) having symptom onset [24] . Regarding epidemiological contact with confirmed case, contact plot was created by using Epicontacts. It is an R 15 package providing a suite of tools aimed at merging line lists and contact data, and providing basic functionality for handling, visualizing and analyzing epidemiological contact data. Maintained as part of the R Epidemics Consortium (RECON), this package is integrated into an ecosystem of tools for outbreak response using the R language. A total of 336 confirmed cases, 261 recovered cases, 69 active cases and 6 deaths were reported from 23 rd March to 13 th July 2020. All confirmed cases were referred to and treated in designated hospital of respective States and Regions. Based on reported data, mean (± SD) age of COVID-19 confirmed cases was 36 (± 15.89) years and so, working age groups were more contracted to infection in both sexes although all age groups could be infected. As shown in Fig. 1 , males were slightly more risk to get infection compared to females. . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted August 4, 2020. . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted August 4, 2020. . https://doi.org/10.1101/2020.08.02.20166504 doi: medRxiv preprint 8 Among 336 confirmed cases, there were 169 cases with reported transmission events. The median serial interval was 4 days (IQR 3, 2-5) with the range of 0 -26 days as shown in Fig. 3 . For 336 confirmed cases through 13 th July 2020, the mean of the reproduction number was 1.44 with (95% CI = 1.30-1.60) by exponential growth method and 1.32 with (95% CI = 0.98-1.73) confident interval by maximum likelihood method (Table 1) . . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted August 4, 2020. . https://doi.org/10.1101/2020.08.02.20166504 doi: medRxiv preprint With regard epidemiological contact, 4 clusters of cases were obviously detected in Myanmar. The first cluster of cases was originated from case-1 to additional (11) confirmed cases out of (137) contact persons. The second cluster of cases was emerged from case-8,11,12,13 to additional (15) confirmed cases out of (714) contact persons. The third cluster of cases was contributed to highest proportion of confirmed cases. It was originated from case-24 to additional (78) confirmed cases among (396) contact persons. The last cluster of cases was originated from case-162 to additional (20) confirmed cases. 9 in ed of to as . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted August 4, 2020. . https://doi.org/10.1101/2020.08.02.20166504 doi: medRxiv preprint 1 0 This study set out to provide epidemiological characteristics and main epidemiological parameters of COVID-19 in Myanmar. Although most cases (242 out of 336 cases) were detected in Yangon Region, the disease has spread to the whole country except one out of fifteen states, regions and union territory within 2 months. Myanmar is one of the least affected countries of COVID-19 in South East Asian Region. Current basic reproduction number (R 0 ) and serial interval was estimated based on available reported data. Unfortunately, the whole-genome sequences of SARS-CoV-2 isolated from confirmed cases in Myanmar is currently unavailable and the strain of coronavirus could not also identify. Since detection of first case of COVID-19 in Myanmar, case fatality rate was 1.79% (6 out of 366). In contrast to mortality rate in South East Asia Region (2.69%) and world population (4.34%), disease mortality was substantially lower [4, 5] . The observed decrease in case fatality rate in Myanmar could be attributed to all laboratory-confirmed cases were admitted to designated specialist hospitals and continuous monitoring of cases for two consecutive negative results during hospitalization. By 13 th July 2020, Myanmar had reported 336 cases, but the outbreak trajectory has been slow compared with neighboring countries such as India, China, Bangladesh and Thailand. This Myanmar is one of the low income countries and resources for diagnostic capacities were limited to compare with developed countries. However, daily test performance was less than one hundred initially, it is significantly growth in testing capacity to more than one thousand per day in recent time. The diagnosis is now focused on people returned back from other countries since mid-May 2020 because the importation of COVID-19 to Myanmar was greatly contributed to daily detection of confirmed cases. So the imported cases were 52.38% of total confirmed cases . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted August 4, 2020. [29, 30] . The longest serial interval was observed about 26 days in Myanmar and hence, 28-days quarantine strategy of MOHS is well covered for all contacts with suspected cases. This study is an epidemiological characteristic of COVID-19 cases in Myanmar, and we recognize the following limitations. First, the actual cases in the country within the study period could be underestimated due to low testing capabilities. Second, the recall bias of cases might have affected data accuracy because of self-reported contact history and symptom onset. Third, with slight inaccuracies of epidemiological information on confirmed cases reported by MOHS, more detailed information regarding date of symptom onset and clinical features were unavailable at the time of analysis. Therefore, dates of test positive of confirmed cases were inferred as the dates of symptom onset to explore the serial interval of transmission event. The . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. The copyright holder for this preprint this version posted August 4, 2020. . https://doi.org/10.1101/2020.08.02.20166504 doi: medRxiv preprint 1 2 closed contacts were identified within a few days after confirmation of their contact history, and were kept at quarantined centers till the result came out. It could be expected that the variation of this duration would be minimal. Fourth, for some patients, the official reports link the person with multiple confirmed cases as contacts. This is not a problem unique to our study but in the other similar studies as well, especially in clusters. This is addressed by considering the earliest confirmed case of the contacts as the source. This study outlined the epidemiological characteristics and epidemic parameters of COVID-19 in Myanmar. The estimation parameters in this study can be comparable with previous documents by others and variability of these parameters can be considered when implementing disease control strategy. Most probably Myanmar is now at mitigation phase because we rarely found on local transmission case in our country. In order to suppress this outbreak, government must be strengthened current successful non-pharmaceutical interventions, maintaining of non-COVID-19 essential health services and maintaining of essential societal services. . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted August 4, 2020. . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. 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The copyright holder for this preprint this version posted August 4, 2020. . https://doi.org/10.1101/2020.08.02.20166504 doi: medRxiv preprintThe copyright holder for this preprint this version posted August 4, 2020. . https://doi.org/10.1101/2020.08.02.20166504 doi: medRxiv preprint