The association of COVID-19 incidence with temperature, humidity, and UV radiation - A global multi-city analysis.

BACKGROUND AND AIM: The associations between COVID-19 transmission and meteorological factors are scientifically debated. Several studies have been conducted worldwide, with inconsistent findings. However, often these studies had methodological issues, e.g., did not exclude important confounding factors, or had limited geographic or temporal resolution. Our aim was to quantify associations between temporal variations in COVID-19 incidence and meteorological variables globally. METHODS: We analysed data from 455 cities across 20 countries from 3 February to 31 October 2020. We used a time-series analysis that assumes a quasi-Poisson distribution of the cases and incorporates distributed lag non-linear modelling for the exposure associations at the city-level while considering effects of autocorrelation, long-term trends, and day of the week. The confounding by governmental measures was accounted for by incorporating the Oxford Governmental Stringency Index. The effects of daily mean air temperature, relative and absolute humidity, and UV radiation were estimated by applying a meta-regression of local estimates with multi-level random effects for location, country, and climatic zone. RESULTS: We found that air temperature and absolute humidity influenced the spread of COVID-19 over a lag period of 15 days. Pooling the estimates globally showed that overall low temperatures (7.5 °C compared to 17.0 °C) and low absolute humidity (6.0 g/m3 compared to 11.0 g/m3) were associated with higher COVID-19 incidence (RR temp =1.33 with 95%CI: 1.08; 1.64 and RR AH =1.33 with 95%CI: 1.12; 1.57). RH revealed no significant trend and for UV some evidence of a positive association was found. These results were robust to sensitivity analysis. However, the study results also emphasise the heterogeneity of these associations in different countries. CONCLUSION: Globally, our results suggest that comparatively low temperatures and low absolute humidity were associated with increased risks of COVID-19 incidence. However, this study underlines regional heterogeneity of weather-related effects on COVID-19 transmission.

Disparities in COVID-19 Impacts on Work Hours and Career Satisfaction by Gender and Race among Scientists in the US: An Online Survey Study

The impact of the COVID-19 pandemic on work-life balance may be unequal between female and male scientists. Further information is needed regarding whether the working conditions and career satisfaction for women and racialized scientists are disproportionately affected by the pandemic. This online survey collected data from 1171 scientists in science, technology, engineering, mathematics (STEM), and medicine (STEMM), public health, or other areas of science/engineering working in the US to examine potential disparities in changes in work hours and career satisfaction by gender and race/ethnicity. A significantly higher percentage of women reported increased work hours compared to men. Women, especially racialized women, experienced disproportionately higher increases in teaching and service than the other groups, which contributed to the increased total work hours for women. Satisfaction with the current career progress was lowest for racialized women compared to their counterparts. Our results indicate that the pandemic has inequitably affected allocation of workloads and career satisfaction by gender and race in scientific fields. Institutions of higher education and other research organizations should acknowledge the gender/race differences in science before and during the pandemic to better support the career development and achievement of all scientists, especially women and even more so racialized women.

Impacts of the COVID-19 pandemic on scientists' productivity in science, technology, engineering, mathematics (STEM), and medicine fields.

While studies suggested adverse impacts of COVID-19 on scientific outputs and work routines for scientists, more evidence is required to understand detailed obstacles challenging scientists' work and productivity during the pandemic, including how different people are affected (e.g., by gender). This online survey-based thematic analysis investigated how the pandemic affected scientists' perception of scientific and academic productivity in the science, technology, engineering, and mathematics (STEM) and medicine fields. The analysis examined if inequitable changes in duties and responsibilities for caregiving for children, family, and/or households exist between scientists who are mothers compared to scientists who are fathers or non-parents. The survey collected data from 2548 survey responses in six languages across 132 countries. Results indicate that many scientists suffered from delays and restrictions on research activities and administrations due to the lockdown of institutions, as well as increased workloads from adapting to online teaching environment. Caregiving responsibility for children and family increased, which compromised time for academic efforts, especially due to the temporary shutdown of social supports. Higher percentages of female parent participants than male parent participants expressed such increased burdens indicating unequal divisions of caregiving between women and men. A range of physical and mental health issues was identified mainly due to overworking and isolation. Despite numerous obstacles, some participants reported advantages during the pandemic including the efficiency of online teaching, increased funding for COVID-related research, application of alternative research methodologies, and fluidity of the workday from not commuting. Findings imply the need for rapid institutional support to aid various academic activities and diminish gender inequity in career development among academicians, highlighting how crisis can exacerbate existing inequalities.

Differences in self-perception of productivity and mental health among the STEMM-field scientists during the COVID-19 pandemic by sex and status as a parent: A survey in six languages.

The COVID-19 pandemic has caused unprecedented challenges for working conditions for scientists, but little is known for how the associations of these challenges with scientists' mental health and productivity differ by sex and status as a parent. This online survey study in six languages collected data from 4,494 scientists in Science, Technology, Engineering, Mathematics, and Medicine fields across 132 countries during October-December 2021. We compared the type of challenges for work, changes in work hours, and perception in productivity during the pandemic by sex and status as a parent (children <18 years living at home). Regression analyses analyzed the impacts of changed working conditions and work-life factors on productivity and mental health. We found that the percentage of participants with increased work hours was the highest in female participants, especially without children. Disproportionately higher increases in work hours were found for teaching and administration in women than men and for research/fundraising in non-parent participants than parent participants (p-value<0.001). Female participants were more concerned about the negative impacts of the pandemic on publications and long-term career progress, and less satisfied with their career progress than their male counterparts. There were differences in the type of institutional actions for the pandemic across study regions. The identified obstacles for work and home-life factors were associated with higher risks of experiencing depression, anxiety, and stress. Decision makers should consider the gender differences in the pandemic's adverse impacts on productivity in establishing equitable actions for career progress for scientists during pandemics.

Association between Short-Term Exposure to Air Pollution and COVID-19 Mortality: A Population-Based Case-Crossover Study Using Individual-Level Mortality Registry Confirmed by Medical Examiners.

BACKGROUND: Studies have suggested links between ambient air pollution and coronavirus 2019 (COVID-19) mortality, yet confirmation by well-designed epidemiological studies with individual data is needed. OBJECTIVES: We aimed to examine whether short-term exposure to air pollution is associated with risk of mortality from COVID-19 for those infected with COVID-19. METHODS: The Cook County Medical Examiner's Office reports individual-level data for deaths from COVID-19 that occur in its jurisdiction, which includes all confirmed COVID-19 deaths in Cook County, Illinois. Case-crossover analysis was conducted to estimate the associations of estimated short-term exposures to particulate matter (PM) with aerodynamic diameter ≤2.5µm (PM2.5) and ozone (O3) on the day of death and up to 21 d before death at location of death with COVID-19. A total of 7,462 deaths from COVID-19 that occurred up to 28 February 2021 were included in the final analysis. We adjusted for potential confounders by time-stratified case-crossover design and by covariate adjustments (i.e., time-invariant factors, meteorological factors, viral transmission, seasonality, and time trend). RESULTS: Of the 7,462 case and 25,457 self-control days, almost all were days with exposure levels below the PM2.5 24-h National Ambient Air Quality Standard (NAAQS) (35 µg/m3); 98.9% had O3 levels below the maximum 8-h NAAQS (35.7 µg/m3 or 70 parts per billion). An interquartile range (IQR) increase (5.2 µg/m3) in cumulative 3-wk PM2.5 exposure was associated with a 69.6% [95% confidence interval (CI): 34.6, 113.8] increase in risk of COVID-19 mortality. An IQR increase (8.2 µg/m3) in 3-d O3 exposure was associated with a 29.0% (95% CI: 9.9, 51.5) increase in risk of COVID-19 mortality. The associations differed by demographics or race/ethnicity. There was indication of modification of the associations by some comorbid conditions. DISCUSSION: Short-term exposure to air pollution below the NAAQS may increase the mortality burden from COVID-19. https://doi.org/10.1289/EHP10836.

Scientific authorship by gender: trends before and during a global pandemic

Many fields of science are still dominated by men. COVID-19 has dramatically changed the nature of work, including for scientists, such as lack of access to key resources and transition to online teaching. Further, scientists face the pandemic-related stressors common to other professions (e.g., childcare, eldercare). As many of these activities fall more heavily on women, the pandemic may have exacerbated gender disparities in science. We analyzed self-identified gender of corresponding author for 119,592 manuscripts from 151 countries submitted January 2019 to July 2021 to the Institute of Physics (IOP) portfolio of 57 academic journals, with disciplines of astronomy and astrophysics, bioscience, environmental science, materials, mathematics, physics, and interdisciplinary research. We consider differences by country, journal, and pre-pandemic versus pandemic periods. Gender was self-identified by corresponding author for 82.9% of manuscripts (N = 99,114 for subset of submissions with gender). Of these manuscripts, authors were 82.1% male, 17.8% female, and 0.08% non-binary. Most authors were male for all countries (country-specific values: range 0.0–100.0%, median 86.1%) and every journal (journal-specific values range 63.7–91.5%, median 83.7%). The contribution of female authors was slightly higher in the pandemic (18.7%) compared to pre-pandemic (16.5%). However, prior to the pandemic, the percent of submissions from women had been increasing, and this value slowed during the pandemic. Contrary to our hypothesis, we did not find that manuscript submissions from women decreased during the pandemic, although the rate of increased submissions evident prior to the pandemic slowed. In both pre-pandemic and pandemic periods, authorship was overwhelmingly male for all journals, countries, and fields. Further research is needed on impacts of the pandemic on other measures of scientific productivity (e.g., accepted manuscripts, teaching), scientific position (e.g., junior vs. senior scholars), as well as the underlying gender imbalance that persisted before and during the pandemic.

Engine emissions with air pollutants and greenhouse gases and their control technologies

Diesel and gasoline are the most used fossil fuels due to their high energy release and low cost for engines. However, the emission of air pollutants and greenhouse gases has caused severe environmental issues, and emission regulations are becoming stricter. Recently, several advances in emission control technologies for fossil fuel engines have been available, which need to be reviewed to manifest future research. Here, we reviewed the primary pollutants emitted from the diesel and gasoline-powered engines, their formation process, and the present technologies to control the emissions of greenhouse gases and air pollutants, especially during the COVID-19 pandemic. In this regard, this review concentrates on a particular matter (PM2.5 and PM10), carbon monoxide (CO), nitrogen oxides (NOx), unburned hydrocarbons (HC), and greenhouse gases (water vapor, CO2, N2O, etc.) as exhaust emissions, the difficulties they cause, and the strategies employed to reduce emissions. This review also provides a framework for understanding how to reduce air pollution and greenhouse gasses generated by diesel and gasoline-powered engines.

Why They Stayed and Why They Left-A Case Study from Ellicott City, MD after Flash Flooding.

Ellicott City, MD was devasted by flash flooding in 2016 and 2018. A lack of qualitative research has been conducted on topics related to sense of place and flash flooding, especially in the United States. In this study, we reveal reasons why some who experienced flash flooding continued to stay the flood zone and why some leave. We utilized a phenomenological approach to answer these research questions. Data were generated through in-depth interviews with 19 participants from the Historic District and adjacent neighborhoods in Ellicott City. The most common reasons participants stayed were: (1) Community Impact, (2) Historical Land, and (3) Financial Burden. The most common reasons participants left were: (1) Emotional Exhaustion and Frustration, (2) Fear/Anxiety, and (3) Financial Burden. The results of our study indicate that reasons individuals who experience flash flooding stay, or leave may include community/historical, environmental, emotional, and economic factors. This reveals the complexity of relocation and sense of place after natural/environmental disasters and supports previous literature that suggests tailored response efforts based on these unique set of burdens. This paper aims to identify burdens and understand flood victims' decisions to help policy makers improve flood response efforts.

Individual and regional characteristics associated with changes in mental health before and during the COVID-19 pandemic in South Korea.

Mental health has been a major public health concerns during the COVID-19 pandemic. This study investigated the effects of COVID-19 on mental health and whether individual and regional characteristics are associated with the changes in mental health. We estimated district-specific changes in the prevalence of moderate stress, extreme stress, and depression before and during the COVID-19 pandemic after adjusting for the time trend of mental health outcomes. Then, a meta-regression was conducted to examine the associations between district-level characteristics and changes in mental health due to the pandemic. The prevalence of moderate stress, extreme stress, and depression increased during the pandemic and the increases were more prominent in districts with high population density and in individuals aged 19-59 years, with a high education level, and with high household income. The % with reduced physical activity due to the pandemic were positively associated with increases in stress; while, the % that have mutual trust among neighbors and the number of sports facilities were negatively associated with increases in stress. Local tax per person had a positive association with increase in depression. Our study provides epidemiological evidence into the mental health consequences of the pandemic, which can inform the priority of resource allocation for managing mental health.

Higher incidence of novel coronavirus (COVID-19) cases in areas with combined sewer systems, heavy precipitation, and high percentages of impervious surfaces.

Combined sewer systems (CSS) are water management systems that collect and transport stormwater and sewer water in the same pipes. During large storm events, stormwater runoff may exceed the capacity of the system and lead to combined sewer overflows (CSOs), where untreated sewer and stormwater are released into the environment. Though current literature reveals inconclusive evidence regarding the infectivity of SARS-CoV-2 in wastewater, detection of infectious SARS-CoV-2 in urine and feces of COVID-19 patients led to concerns that areas contaminated by CSOs may be a reservoir of SARS-CoV-2 and may result in illness after the ingestion and/or inhalation of contaminated splashes, droplets, or aerosols. We investigated the association between COVID-19 incidence and CSSs and whether this association differed by precipitation and percent impervious surfaces as a proxy for possible CSOs. We fitted a quasi-Poisson regression model to estimate the change in percentage of incidence rate of COVID-19 cases in counties with a CSS compared to those without, adjusting for potential confounders (i.e., state, population density, date of first documented COVID-19 case, social vulnerability, and percent vaccinated) and including interaction variables between CSS, precipitation, and impervious surfaces. Our findings suggest that heavy precipitation in combination with high percentages of imperviousness is associated with higher incidences of COVID-19 cases in counties with a CSS compared to in counties without (p-value = 2.5e-9). For example, CSS-counties with precipitation of 10 in/month may observe a higher incidence in COVID-19 cases compared to non-CSS counties if their impervious surfaces exceed 33.5% [95%CI: 23.0%, 60.0%]. We theorize that more COVID-19 cases may be seen in counties with a CSS, heavy precipitation, and high percentages of impervious surfaces because of the possible increase in frequency and severity of CSOs. The results suggest links between climate change, urbanization, and COVID-19.

Temporal transition of racial/ethnic disparities in COVID-19 outcomes in 3108 counties of the United States: Three phases from January to December 2020.

Early studies reported higher risk of COVID-19 outcomes for racial/ethnic minorities in the early phase of the pandemic in the United States. While the initial surge of COVID-19 was concentrated in some areas, COVID-19 became pervasive across the entire continent with high impacts in the northern region and central region in the end of 2020. With this geographical transition, we aim to investigate patterns of these racial/ethnic disparities over time. We assessed associations of percentage of race/ethnic minorities and racial segregation indexes with COVID-19 case and mortality rates in 3108 counties of the continental United States during the pandemic's early phase, second, and third phase (January 21-June 15, June 16-August 31, and September 1-December 18, 2020, respectively). We adjusted for population density, age, and sex. We tested whether time-varying associations were consistent across climate regions and explained by socioeconomic variables. In the early phase, counties with higher percentage of Black/African Americans and higher Black-White segregation had higher COVID-19 case and mortality rates. These associations decreased over time and reversed in the third phase. Associations between Hispanic and COVID-19 outcomes were positive in all periods, but more so early in the pandemic. Higher COVID-19 case rates for counties with higher non-Hispanic White population emerged in the third phase. These trends were similar across climate regions, and socioeconomic variables did not explain these trends. In summary, county-level racial/ethnic disparities of COVID-19 are not stationary but change over the course of the pandemic, suggesting complex social, cultural, and political influences.

Impact of Changed Use of Greenspace during COVID-19 Pandemic on Depression and Anxiety.

The COVID-19 pandemic has had devastating consequences for health, social, and economic domains, but what has received far less focus is the effect on people's relationship to vital ecological supports, including access to greenspace. We assessed patterns of greenspace use in relation to individual and environmental factors and their relationship with experiencing psychological symptoms under the pandemic. We conducted an online survey recruiting participants from social media for adults in Korea for September-December 2020. The survey collected data on demographics, patterns of using greenspace during the pandemic, and major depression (MD) and generalized anxiety disorder (GAD) symptoms. The Patient Health Questionnaire (PHQ-9) and the Generalized Anxiety Disorder 2-item (GAD-2) were applied to identify probable cases of MD and GAD. A logistic regression model assessed the association decreased visits to greenspace after the outbreak compared to 2019 and probable MD and GAD. Among the 322 survey participants, prevalence of probable MD and GAD were 19.3% and 14.9%, respectively. High rates of probable MD (23.3%) and GAD (19.4%) were found among persons currently having job-related and financial issues. Of the total participants, 64.9% reported decreased visits to greenspace after the COVID-19 outbreak. Persons with decreased visits to greenspace had 2.06 higher odds (95% CI: 0.91, 4.67, significant at p < 0.10) of probable MD at the time of the survey than persons whose visits to greenspace increased or did not change. Decreased visits to greenspace were not significantly associated with GAD (OR = 1.45, 95% CI: 0.63, 3.34). Findings suggest that barriers to greenspace use could deprive people of mental health benefits and affect mental health during pandemic; an alternative explanation is that those experiencing poor mental health may be less likely to visit greenspaces during pandemic. This implies the need of adequate interventions on greenspace uses under an outbreak especially focusing on how low-income populations may be more adversely affected by a pandemic and its policy responses.

Gender Differences in First and Corresponding Authorship in Public Health Research Submissions During the COVID-19 Pandemic.

Objectives. To investigate the rate of manuscript submission to a major peer-reviewed journal (American Journal of Public Health) by gender, comparing periods before and during the pandemic.Methods. We used data from January 1 to May 12, 2020, and defined the start of the pandemic period by country as the first date of 50 or more confirmed cases. We used an algorithm to classify gender based on first name and nation of origin. We included authors whose gender could be estimated with a certainty of at least 95%.Results. Submission rates were higher overall during the pandemic compared with before. Increases were higher for submissions from men compared with women (41.9% vs 10.9% for corresponding author). For the United States, submissions increased 23.8% for men but only 7.9% for women. Women authored 29.4% of COVID-19-related articles.Conclusions. Our findings suggest that the pandemic exacerbated gender imbalances in scientific research.

Urban environments and COVID-19 in three Eastern states of the United States.

The United States has the highest numbers of confirmed cases and deaths during the novel coronavirus disease 2019 (COVID-19) pandemic. Previous studies reported that urban residents are more vulnerable to the spread and mortality of COVID-19 than rural residents. However, the pathways through which urban environments affect COVID-19 spread and mortality are unclear. We collected daily data on the number of confirmed cases and deaths of COVID-19 from Mar. 01 to Nov. 16, 2020 for all 91 counties in New York, New Jersey, and Connecticut in the United States. We calculated the COVID-19 incidence %, daily reproduction number, and mortality %, then estimated the associations with urban environment indicators using regression models. COVID-19 outcomes were generally highest in areas with high population density, and this pattern was evident in the early period of epidemic. Among the area-level demographic variables, the percentage of Black or Hispanic residents showed the strongest positive association with COVID-19 outcomes. Higher risk of COVID-19 outcomes was also associated with higher percentage of overcrowded households, uninsured people, and income inequality. The percent elderly, sex ratio (the ratio of males to females), and greenness were negatively associated with risk of COVID-19 outcomes. The results of this study could indicate where resources are most needed.

Guidelines for Modeling and Reporting Health Effects of Climate Change Mitigation Actions.

BACKGROUND: Modeling suggests that climate change mitigation actions can have substantial human health benefits that accrue quickly and locally. Documenting the benefits can help drive more ambitious and health-protective climate change mitigation actions; however, documenting the adverse health effects can help to avoid them. Estimating the health effects of mitigation (HEM) actions can help policy makers prioritize investments based not only on mitigation potential but also on expected health benefits. To date, however, the wide range of incompatible approaches taken to developing and reporting HEM estimates has limited their comparability and usefulness to policymakers. OBJECTIVE: The objective of this effort was to generate guidance for modeling studies on scoping, estimating, and reporting population health effects from climate change mitigation actions. METHODS: An expert panel of HEM researchers was recruited to participate in developing guidance for conducting HEM studies. The primary literature and a synthesis of HEM studies were provided to the panel. Panel members then participated in a modified Delphi exercise to identify areas of consensus regarding HEM estimation. Finally, the panel met to review and discuss consensus findings, resolve remaining differences, and generate guidance regarding conducting HEM studies. RESULTS: The panel generated a checklist of recommendations regarding stakeholder engagement: HEM modeling, including model structure, scope and scale, demographics, time horizons, counterfactuals, health response functions, and metrics; parameterization and reporting; approaches to uncertainty and sensitivity analysis; accounting for policy uptake; and discounting. DISCUSSION: This checklist provides guidance for conducting and reporting HEM estimates to make them more comparable and useful for policymakers. Harmonization of HEM estimates has the potential to lead to advances in and improved synthesis of policy-relevant research that can inform evidence-based decision making and practice. https://doi.org/10.1289/EHP6745.

Relationships between Local Green Space and Human Mobility Patterns during COVID-19 for Maryland and California, USA

Human mobility is a significant factor for disease transmission. Little is known about how the environment influences mobility during a pandemic. The aim of this study was to investigate an effect of green space on mobility reductions during the early stage of the COVID-19 pandemic in Maryland and California, USA. For 230 minor civil divisions (MCD) in Maryland and 341 census county divisions (CCD) in California, we obtained mobility data from Facebook Data for Good aggregating information of people using the Facebook app on their mobile phones with location history active. The users’movement between two locations was used to calculate the number of users that traveled into an MCD (or CCD) for each day in the daytime hours between 11 March and 26 April 2020. Each MCD’s (CCD’s) vegetation level was estimated as the average Enhanced Vegetation Index (EVI) level for 1 January through 31 March 2020. We calculated the number of state and local parks, food retail establishments, and hospitals for each MCD (CCD). Results showed that the daily percent changes in the number of travels declined during the study period. This mobility reduction was significantly lower in Maryland MCDs with state parks (p-value = 0.045), in California CCDs with local-scale parks (p-value = 0.048). EVI showed no association with mobility in both states. This finding has implications for the potential impacts of green space on mobility under an outbreak. Future studies are needed to explore these findings and to investigate changes in health effects of green space during a pandemic.

Reductions in mortality resulting from reduced air pollution levels due to COVID-19 mitigation measures.

To control the novel coronavirus disease (COVID-19) outbreak, state and local governments in the United States have implemented several mitigation efforts that resulted in lower emissions of traffic-related air pollutants. This study examined the impacts of COVID-19 mitigation measures on air pollution levels and the subsequent reductions in mortality for urban areas in 10 US states and the District of Columbia. We calculated changes in levels of particulate matter with aerodynamic diameter no larger than 2.5 µm (PM2.5) during mitigation period versus the baseline period (pre-mitigation measure) using the difference-in-difference approach and the estimated avoided total and cause-specific mortality attributable to these changes in PM2.5 by state and district. We found that PM2.5 concentration during the mitigation period decreased for most states (except for 3 states) and the capital. Decreases of average PM2.5 concentration ranged from 0.25 µg/m3 (4.3%) in Maryland to 4.20 µg/m3 (45.1%) in California. On average, PM2.5 levels across 7 states and the capital reduced by 12.8%. We estimated that PM2.5 reduction during the mitigation period lowered air pollution-related total and cause-specific deaths. An estimated 483 (95% CI: 307, 665) PM2.5-related deaths was avoided in the urban areas of California. Our findings have implications for the effects of mitigation efforts and provide insight into the mortality reductions can be achieved from reduced air pollution levels.

COVID-19 in South Korea: epidemiological and spatiotemporal patterns of the spread and the role of aggressive diagnostic tests in the early phase.

BACKGROUND: South Korea experienced the novel coronavirus disease (COVID-19) outbreak in the early period; thus data from this country could provide significant implications for global mitigation strategies. This study reports how COVID-19 has spread in South Korea and examines the effects of rapid widespread diagnostic testing on the spread of the disease in the early epidemic phase. METHODS: We collected daily data on the number of confirmed cases, tests and deaths due to COVID-19 from 20 January to 13 April 2020. We estimated the spread pattern with a logistic growth model, calculated the daily reproduction number (Rt) and examined the fatality pattern of COVID-19. RESULTS: From the start date of the epidemic in Korea (18 February 2020), the time to peak and plateau were 15.2 and 25 days, respectively. The initial Rt was 3.9 [95% credible interval (CI) 3.7 to 4.2] and declined to <1 after 2 weeks. The initial epidemic doubling time was 3.8 days (3.4 to 4.2 days). The aggressive testing in the early days of the epidemic was associated with reduction in transmission speed of COVID-19. In addition, as of 13 April, the case fatality rate of COVID-19 in Korea was 2.1%, suggesting a positive effect of the targeted treatment policy for severe patients and medical resources. CONCLUSIONS: Our findings provide important information for establishing and revising action plans based on testing strategies and severe patient care systems, needed to address the unprecedented pandemic.