key: cord-0752528-ntaem4x7 authors: Lee, Hocheol; Park, Sung Jong; Lee, Ga Ram; Kim, Ji Eon; Lee, Ji Ho; Jung, Yeseul; Nam, Eun Woo title: The Relationship between the COVID-19 Prevalence Trend and Transportation Trend in South Korea date: 2020-05-14 journal: Int J Infect Dis DOI: 10.1016/j.ijid.2020.05.031 sha: c90f0c81cba97cfa42af1aa6fbd1442be48d1bba doc_id: 752528 cord_uid: ntaem4x7 Abstract Objective World Health Organization (WHO) declared a pandemic on March 12th, 2020. Several studies indicate that these densely populated urban environments and the heavy dependence on traffic could increase the potential spread of COVID-19. This study investigated the association between changes in traffic volume and the spread of COVID-19 in South Korea. Methods This study analyzed the daily national traffic and traffic trend for 3 months from January 1st, 2020. Traffic data was measured by the 6,307 vehicle detection system (VDS). This study analyzed the traffic gap between 2019 and 2020. And non-linear regression was performed to analyze the change in traffic trend in 2020. The relationship between traffic and COVID-19 confirmed cases was analyzed using single linear regression. Results The mean daily nationwide in 2020 was 143,655,563 vehicles, which was 9.7% lower than the same period in 2019 (159,044,566 vehicles). All regions showed a decreasing trend for traffic in February, which shifted to an increasing trend from March. In Incheon, there only was a positive but insignificant (β = 43,146, p = .056) linear relationship with the increasing numbers of new confirmed cases associated with increased traffic. Conclusions New confirmed COVID-19 patients have been decreasing since March, while the traffic has been increasing. Particularly, the fact that traffic is increasing indicates greater contact between people, which in turn increases the risk of COVID-19 spread. Therefore, the government will need to devise suitable policies, such as total social distancing. Following the first COVID-19 patient in Wuhan, China in December 2019, the disease spread rapidly to over 60 countries in 2020. Consequently, the World Health Organization (WHO) declared a pandemic on March 12 th , 2020, within 71 days of the first case (Zhu et al., 2020; World Health Organization, 2020) . As of March 31 st , COVID-19 was detected in 206 countries, with 770,138 confirmed patients and 36,796 deaths worldwide (WHO, 2020b) . Different countries are employing diverse methods to manage and prevent the further spread of COVID-19 (WHO, 2020a) . Most countries are limiting contact between citizens, most notably China, where Wuhan was placed under lockdown within just 23 days of the outbreak, and contact with neighboring cities was forbidden (Lin et al., 2020) . France, Switzerland, and Austria closed their borders on March 17 th , while France, Spain, Italy, Germany, and some states in the US have been implementing strict policies to limit contact between citizens, including nationwide stay-at-home orders, thereby preventing the domestic spread of COVID-19 (Kinross et al. 2020 ). South Korea's total population is 51.8 million, of which a large proportion resides or is active in the capital and the surrounding Gyeonggi Province. Of the total population, 13.28 million (26.0%), 9.73 million (18.7%), and 2.95 million (5.7%) reside in Gyeonggi Province, Seoul, and Incheon, respectively (Resident, 2020) . Several studies indicate that these densely populated urban environments and the heavy dependence on public transport could increase the potential spread of COVID-19 (Choi and Ki, 2014; Korean Society of Infectious Diseases et al., 2020; BBC News, 2020; Shim et al., 2020) . On March 2 nd , the South Korean government initially postponed the commencement of elementary, middle, and high schools for 4 weeks J o u r n a l P r e -p r o o f until April 6 th and of university classes until March 16 th , before switching to online classes until April 16 th . Some schools have decided to conduct online classes for the entire first semester (Koh and Hoenig, 2020) . Due to joint efforts, including public institutions, private enterprises, other companies implementing work-from-home systems to minimize travel, preventive education for citizens via social distancing campaigns, preparation of disinfectant in every building and street, and information transparency regarding the movements and locations of confirmed patients, a decreasing trend is being observed in the daily number of new COVID-19 patients. Based on existing studies, although the number of new COVID-19 patients in South Korea shows a decreasing trend, the global number of COVID-19 cases, including South Korea, is forecast to eventually increase again, possibly due to genetic mutations in the virus, re-influx from overseas, and decreasing compliance of the public (Liu et al. 2020; Verity et al. 2020; Zhan et al. 2020) . Particularly, unlike in Spain, the US, and the UK, outdoor excursions are not restricted in South Korea. Therefore, it is predicted that, as citizens adapt to COVID-19, activity levels will increase and adherence will decrease for measures such as staying indoors, social distancing, and always wearing a mask, resulting in a secondary outbreak of COVID-19 (Zhan et al. 2020) . Research analyzing 10 years of data found a strong correlation between infectious diseases and traffic volume; specifically, increased traffic during an infectious disease outbreak is associated with greater spread (Meloni et al. 2009; Wu et al. 2019 ). On analyzing 10 types of influenza from the last 300 years, a very close association with traffic was found. A disease that took 1 year to spread 300 years ago would now be able to reach anywhere in the world within a day due to the development of traffic (Rodrigue et al., 2020) . This study investigated the association between changes in traffic volume and the spread of COVID-19 in South Korea, and provided predictive data required for future infectious disease prevention policies. This quasi-experimental serial study analyzed the daily national traffic in South Korea for 3 months between January 1 st and March 31 st , 2020, since the first COVID-19 patient in South Korea was observed in January. The data was compared with traffic from the same period the previous year (i.e., January 1 st to March 31 st , 2019) to investigate the changes in traffic. The following secondary data was used to analyze the nationwide traffic according to trends in COVID-19. First, a suitable data set was constructed using the point data for traffic provided in the public data portal of the Korea Expressway Corporation (http://data.ex.co.kr/portal/fdwn/view?type=VDS&num=37&requestfrom=dataset#) and the public data on confirmed COVID-19 patients released by the Korea Centers for Disease Control and Prevention (KCDC) (KCDC, 2020). The point traffic data from the Korea Expressway Corporation was measured by the vehicle detection systems (VDS); traffic data was produced by measuring/collecting the traffic passing over specific points with an installed VDS. The VDS included in-ground ( Figure 1) and above-ground sensors ( Figure 2 ). The data set included data collected from 7,488 VDS J o u r n a l P r e -p r o o f nationwide. We excluded 1,181 VDS without GIS WGS84 coordinates and used the data from a total of 6,307 VDS. The map in Figure 3 displays the included VDS as round dots. [Insert Figure 1 - Figure 3 here] COVID-19 patient trends in South Korea were analyzed using the statistics from the KCDC on "daily new confirmed patient count" and "cumulative number of individuals released from isolation." The regional statistics for daily new confirmed patients and cumulative number of individuals released from isolation were obtained by visiting the individual city/province/county's homepage, and a suitable data set was constructed for this study. First, the mean daily nationwide traffic was calculated for each week starting from January 1 st , 2020 to compare traffic volumes between 2019 and 2020. This was done because the 2020 data included the date of February 29 th . The mean daily nationwide traffic was compared between 2019 and 2020 using the following equation: This study analyzed traffic volumes according to the trends in the spread of COVID- In the first week of February, nationwide traffic was 23.3% lower than in 2019. Thereafter, the nationwide traffic in February continued to decrease, and in the fourth week of February, it was 26.1% lower than in 2019. In March 2020, nationwide traffic shifted to an increasing trend from March 7 th onwards. Compared to the same period in 2019, traffic was lower throughout March (first week: ▼25.1%, second week: ▼14.6%, third week: ▼13.7%, fourth week: ▼14.0%, fifth week: J o u r n a l P r e -p r o o f ▼22.0%). However, as shown by the 2020 traffic trend curve, displayed as a red line in Figure 4 , the nationwide traffic showed an increasing trend. The mean daily nationwide traffic between January 1 st and March 31 st in 2020 was 143,655,563 vehicles, which was 9.7% lower than the same period in 2019 (159,044,566 vehicles) ( Table 1) . [Insert Table 1 here] As shown by the regional traffic trend curves in Figure 4 , all regions showed a decreasing trend for traffic in February, which shifted to an increasing trend from March. Particularly, there was almost no change in traffic in Seoul, and Incheon showed a continuous decrease in traffic from January that shifted to an increasing trend from the end of February. In Gyeonggi, traffic increased in January, showed a slight decrease after the first COVID-19 case, and then switched to an increasing trend again from March 7 th . In Sejong, the traffic suddenly increased in March. In Daegu, the traffic decreased significantly compared to other regions in February, and shifted to an increasing trend in March; however, overall traffic was still low. In Figure 4 , the first COVID-19 patient in South Korea is displayed as a vertical dotted line on January 19 th , the daily new confirmed cases are displayed as a blue line, and the cumulative number released from isolation is displayed as green squares, corresponding to the right-hand y-axis. J o u r n a l P r e -p r o o f [Insert Table 2 here] Types of relationship between regional traffic and COVID-19 The analyses in Table 2 , Figure 4 , and Figure 5 have been converted into types for each region in Table 3 based on whether the relationship between traffic and COVID-19 was an increasing or decreasing relationship. Incheon was categorized as a region requiring strong control (Type 1), with increasing trends for both the COVID-19 spread and traffic. Gyeonggi and Seoul were categorized as regions in the early stages of focused control or requiring control (Type 2), with increasing traffic but a relatively flat trend for new confirmed COVID-19 cases. The other regions were categorized as stable (Type 3), with increasing traffic but decreasing trends for COVID-19 spread. [Insert Table 3 here] This study analyzed the relationship between traffic trends and the spread of COVID-19 after the first COVID-19 patient was confirmed in South Korea at both the national and the regional level. Since the first confirmed patient in South Korea on January 19 th , the mass media (e.g., TV news, newspapers, Internet) and previous studies have shown a decrease in peoples' engagement in outdoor activities as a result of self-isolation, working from home, voluntarily staying indoors, delaying the commencement of schools and universities, and delivering educational messages for COVID-19 prevention (e.g., Internet, broadcast media, written J o u r n a l P r e -p r o o f articles) (Chinazzi et al. 2020; Magal and Webb 2020) . Similarly, in the present study, following the COVID-19 outbreak in South Korea, nationwide traffic decreased by 9.7% compared to 2019, indicating a decrease in citizens' outdoor activities. Particularly, after the KCDC raised the infectious disease alert level to "Orange" on January 27 th , a large decrease was observed in nationwide traffic, and after the alert level was raised to "Red" on February 22 nd , the traffic in the fourth week of February decreased by 26.1% compared to 2019 ( Figure 4 ). (Won, 2020) . Second, employees following work-from-home policies since February started commuting to work again once the spread of COVID-19 decreased in March, and this led to increased traffic. Indeed, employees working from home were at their highest levels of movement in the first week of March, after which they showed a decreasing trend. Third, citizens who had previously used public transport (the Metro, buses, taxis, etc.) showed increased use of their personal vehicles for outings to avoid public transport, which is susceptible to COVID-19 spread. Fourth, South Korea is a country with four seasons, and has a culture where people frequently go out in the spring time. The culture, sports, and tourism ministries in individual cities, provinces, and counties attempted to prevent outdoor activities by closing or reducing the operating hours of major tourism sites; however, the number of tourists visiting these sights increased as the weather got warmer. When the regional COVID-19 trends and traffic trends were analyzed in this study, the traffic in Seoul, Gyeonggi, and Incheon showed smaller changes compared to the other regions. This is because the Korean citizens, including overseas students, started returning to the country as COVID-19 began rapidly spreading overseas, such as in Europe and the US (Cho 2020 ). The number of Korean citizens returning from overseas and requiring control was estimated to be 210,000 individuals, because of which the risk of re-influx of COVID-19 is considerably high. Besides, 23.8% of the confirmed cases in Seoul in the third week of March were individuals returning from abroad (Young-kyung, 2020). Thus, Seoul, Gyeonggi, and Incheon, which are closer to the airport and the residence of many citizens returning from abroad, showed increased COVID-19 and traffic trends as compared to other regions. Particularly, Incheon showed a positive linear relationship between traffic and new confirmed COVID-19 patients, indicating an increasing concern about a secondary COVID-19 outbreak in this region compared to others. This study has some limitations. Frist, this study does not collect all national traffic volume. VDS installed part of main load. Therefore, this data does not reflect the national traffic volume, but this VDS measure indicator has representation. And this data does not delete include traffic volume for drive-through station. Because it is difficult to collect the traffic data for drive through. In future, it is necessary to conduct by deleting the drive through traffic data. This study analyzed the nationwide traffic and spread of COVID-19 in South Korea after the country's first case. Nationwide traffic in 2020 decreased by 9.7% compared to 2019. Particularly, when the KCDC raised the infectious disease alert level to "Orange," there was an initial decrease in nationwide traffic, and when the alert level was raised to "Red," there was a second decrease in national traffic. In the same period, the number of COVID-19 patients and the rate of spread also increased. In South Korea, the number of new confirmed COVID-19 patients has been decreasing since March, while the traffic has been increasing. However, it will be necessary to use accurate data to analyze circumstances in the event of a secondary outbreak of COVID-19 due to increased traffic and re-influx from the overseas, and to prepare policies and equipment to cope with such a secondary outbreak. Particularly, the fact that traffic is increasing indicates greater contact between people, which in turn increases the risk of COVID-19 spread. Therefore, the government will need to devise suitable policies, such as total social distancing. Not applicable. The first author, LHC, and the corresponding author, NEW, were responsible for the idea for the paper, the methodology, the analysis, and the draft. PSH was responsible for the analysis, LGR for data cleaning, and KJE for the data results and discussion. Additionally, LJH processed the GIS location coordinates, and JY participated in debates and discussions. All the authors diligently participated in reviewing the paper. This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. Ethical approval or individual consent was not applicable. The authors declare that they have no known competing financial interests or personal relationships that could have influenced the work reported in this paper. First, we would like to express our gratitude to everyone working to overcome COVID-19, in South Korea and throughout the world. We would also like to thank our collaborators at Yonsei Global Health Center, who helped us with research on global COVID-19 trends and international healthcare, and the collaborating researchers worldwide. All data and materials used in this work were publicly available. J o u r n a l P r e -p r o o f Coronavirus: South Korea declares highest alert as infectious surge The effect of travel restrictions on the spread of the COVID-19 and Inter-Korean Health Care Security Community. 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