The Changes in Epidemiology of Visiting Emergency Department at COVID-19

On December 31, 2019, a type of pneumonia with unknown origin was reported in Wuhan, China. It was named as coronavirus disease 2019 by the World Health Organization. Several studies showed that the outbreaks of infectious diseases affect the emergency department visits. Therefore, this study aimed to identify the epidemiological characteristics of patients visiting the emergency department during the coronavirus disease outbreak. Method This retrospective observational study was conducted in the three tertiary emergency departments. To evaluate the general characteristics of patients visiting the emergency department, data on sex, age, date and time of visit, initial blood pressure, heart rate, respiration rate, body temperature, level of consciousness, and disposition upon discharge were collected. Results A total of 180,192 patients were enrolled in this study. There were 52,245 patients who visited the emergency department during the coronavirus disease outbreak (December 2019–April 2020). This number was signicantly reduced compared with the 64,405 and 63,542 patients who visited during the pre-coronavirus disease period. During the period of coronavirus disease outbreak, the proportion of alert patients began to decline from February to April. Also, the proportions of patients with Korean Triage and Acuity scores 4–5 and discharged patients decreased during the same period. The number of patients who were diagnosed with “inuenza because of identied seasonal inuenza virus” decreased to 1,507 (2.9%), compared with the 2,131 (3.4%) and 2,157 (3.3%) patients diagnosed with this condition during the pre-coronavirus disease period. Conclusion The study showed changes in the patterns of emergency department visits during the coronavirus disease outbreak. During this period, the total number of patients and non-emergency patients visiting the emergency department decreased.


Introduction
On December 31, 2019, a type of pneumonia with unknown origin was reported in Wuhan, the central city and the capital of Hubei Province, China. It was reported to be caused by a novel coronavirus known as severe acute respiratory syndrome coronavirus 2 and was named as coronavirus disease 2019 (COVID-19) by the World Health Organization on February 12, 2020 (1)(2)(3).
Several strains of coronaviruses can infect humans and animals, and approximately 15%-30% of the cases of common colds are caused by a human coronavirus. Similar to severe acute respiratory syndrome coronavirus outbreak and Middle East respiratory syndrome coronavirus (MERS-CoV) outbreak, some strains of coronaviruses that cause zoonotic infections may spread from animals to humans (4,5). A coronavirus causes respiratory illnesses such as pneumonia and acute respiratory distress syndrome, resulting in death because of respiratory failure and sepsis (3,6).
In Korea, COVID-19 was rst identi ed on January 20, 2020, from a Chinese female tourist residing in Wuhan. After the superspreading event around mid-February, the number of con rmed cases began to rise sharply and reached more than a thousand (10). As of June 1, 6,080,000 patients and 124,000 deaths were reported worldwide, and 11,503 patients with con rmed COVID-19 and 271 deaths were reported in Korea (14,15).
Several studies showed that the outbreaks of infectious diseases affect the emergency department (ED) visits. During the Escherichia coli 0157:H7 outbreak in the United States in 1993 and the H1N1 in uenza pandemic in 2009, the number of ED visits increased. During the SARS outbreak in 2003 and MERS outbreak in 2014, the number of ED visits decreased (16)(17)(18)(19). To date, no study has evaluated the pattern of ED visits during the period of COVID-19 outbreak. Therefore, this study aimed to identify the epidemiological characteristics of patients visiting the ED during period of COVID-19 outbreak.

Design and setting
This retrospective observational study was conducted in three tertiary EDs in Korea University Hospitals. Two of these EDs are regional EDs in Seoul, and 49,994 and 64,456 patients, respectively, visited these EDs in 2019. One of these EDs is a local ED in Ansan, Gyeonggi-do and is visited by 47,933 patients each year. To examine the effect of COVID-19 on the pattern of ED visits, we collected the data of patients who visited the ED for 6 months from December 1, 2019, to April 30, 2020. This period was referred to as the COVID-19 period. The pattern of ED visits during this period was compared with that during the period from December 1, 2018, to April 30, 2019, and from December 1, 2017, to April 30, 2018, also referred to as the pre-COVID-19 period.

Ethical statement
The study protocol is performed in accordance with the relevant guidelines. The requirement for informed consent was waived by Institutional Review Board of Korea University. Because this is a retrospective observational study and the data was extracted without identifying the study participants' personal information, informed consent was not sought for the present study. This study was reviewed and approved by the Institutional Review Board of Korea University. (IRB no.: 2020GR0208).

Measurements
To evaluate the general characteristics of patients visiting ED, data on sex, age, date and time of visit, initial blood pressure, heart rate, respiration rate, body temperature, level of consciousness, and disposition upon discharge were collected. The Korean Triage and Acuity Scale (KTAS) was used as a triage tool to assess the severity. KTAS was used as a trial tool in all regional and local EDs in Korea and was divided into ve levels. Individuals with KTAS scores from 1 to 3 were generally classi ed as emergency patients, and those with KTAS scores 4-5 were classi ed as non-emergency patients (20). To identify the changes in the pattern of disease of patients who visited the ED during the study period, the diagnosis was made using the International Classi cation of Case, 10th revision (ICD-10) codes. The extracted ICD-10 code comprised three characters, and only the primary diagnosis was recorded per one patient.

Statistical analyses
The SPSS Statistics (SPSS 20.0, IBM, Armonk, NY, USA) was used to perform all statistical analyses. The continuous variables were expressed as means ± standard deviations. and the categorical variables were expressed as frequencies (percentages). To analyze the difference between the means of the three groups, a normality test was performed using the Kolmogorov-Smirnov test, and the homogeneity of variance was checked using the Levene's test. The test results indicated a normal variance although not homogeneity, and the difference in the number of samples among the three groups was relatively large. Therefore, the analysis was performed using Welch's robust analysis of variance, and post hoc analysis was performed following the Dunnett T3 method. To identify the correlation among categorical variables, the χ 2 test was performed. A P value of < 0.05 was considered signi cant.

Results
Differences in the number of patients visiting the ED A total of 191,217 patients visited the ED during the study period. However, patients whose visits were non-medical in nature, such as issuance of medical certi cates and cancellation of reception, and those who lacked data in their medical records were included. Overall, 180,192 patients were enrolled in the study. 52,245 patients visited the ED during the COVID-19 period (December 2019-April 2020). This number was signi cantly reduced compared with the 64,405 and 63,542 patients who visited the ED during the pre-COVID-19 period (December 2017-April 2018 and December 2018-April 2019, respectively) ( Fig.  1). The patterns of ED visits signi cantly decreased in February, March, and April (Fig. 2).
Changes in the characteristics of patients visiting the ED Table 1 shows the general characteristics of each year during the study period. The mean age of patients who visited the ED during the COVID-19 period (43.5 ± 26.1) was signi cantly higher than those who visited the ED during the pre-COVID-19 period (40.2 ± 26.4 vs 41.1 ± 26.3) (P < 0.001). No signi cant difference was observed in the annual number of patients who visited the ED during the study period between sexes (P = 0.0756). However, signi cant differences were observed in the visiting reason with a medical or non-medical disease, the level of consciousness, initial KTAS, and disposition (P < 0.001). Approximately 77.3% of the patients had medical illness during the COVID-19 period. This proportion increased compared with those (74.0% and 75.1%) reported during the pre-COVID-19 period. The proportion of alert patients during the COVID-19 period was around 94.2%, which was lower than those who visited the ED (95.5% and 95.3%) during the pre-COVID-19 period. Approximately 37.3% of the patients had KTAS scores 4-5 during the COVID-19 period, which was lower than those (42.1% and 41.6%) reported during pre-COVID-19 period. In contrast, the proportion of admission during the COVID-19 period increased to 23.3%, compared with those (19.5% and 20.9%) reported during the pre-COVID-19 period (Table 1).
During the COVID-19 period, the proportion of alert patients started to decline from February to April (Fig. 3). In addition, the proportion of patients with KTAS scores 4-5 and discharged patients decreased during the same period ( Fig. 4-5). However, the mean ages of patients who visited the ED increased during the same period (Fig. 6). Comparing the pattern of patients visiting the ED by time zone, the number of patients coming to the ED decreased during COVID-19 period. Especially in the morning (6:00 to 12:00), afternoon (12:00 to 18:00), and evening (18:00 to 00:00). At night time (0:00 to 6:00), the decrease was also shown but not much as other times. (Fig. 7).
Changes in the patterns of disease in patients visiting the ED The three most common diagnoses prompting an ED visit during the COVID-19 period and pre-COVID-19 period were "abdominal and pelvis pain," "fever of other and unknown origin," and "open wound in the head" and remained unchanged during the study period. During the COVID-19 period, the number of patients who were diagnosed with "in uenza because of an identi ed seasonal in uenza virus" decreased (1,507 (2.9%)), compared with those (2131 (3.4%) and 2157 (3.3%)) reported in the pre-COVID-19 period. Some patients were diagnosed with "in uenza because of an identi ed seasonal in uenza virus" among the top 10 diagnoses after February during the pre-COVID-19 period. However, there were no included diagnostic cases after February in COVID-19 period. "Other gastroenteritis and colitis of infectious and unspeci ed origin," which was included in the top 10 diagnoses prompting an ED visit during the pre-COVID-19 period, was not included in the top 10 diagnoses during the COVID-19 period. Furthermore, "other sepsis" was initially included in the top 10 diagnoses after February during the COVID-19 period, although not in the top 10 diagnoses during the pre-COVID-19 period (Table 2).

Discussion
This is the rst study to show the changes in the characteristics of patients visiting the ED during the COVID-19 period. During the COVID-19 period, the total number of patients visiting the ED decreased, and the proportion of patients who visited the ED because of a disease increased. The number of patients with a KTAS score 4-5 that was classi ed as non-emergency patients, and the proportion of alert patients decreased. The rate of admission increased during the COVID-19 period. These trends had stood out since February when the number of patients were strikingly increased. From March 22 to May 5 in 2020, the government implemented "social distancing," but there was no obvious difference compared with that in February.
Worldwide, non-emergency patients who do not need to visit the ED were markedly increased. Some studies reported that 30%-50% of the patients who visited the ED are classi ed as non-emergency patients (21)(22)(23)(24)(25). The same situation was reported in this study. About 42% of patients were classi ed as non-emergency patients (KTAS scores 4-5) during the pre-COVID-19 period. However, the number of non-emergency patients decreased during the COVID-19 period.
During the SARS outbreak in 2009, the infection spread in the hospital. Similarly, when MERS outbreak occurred in Korea in 2015, one patient with con rmed MERS infected 81 patients in the ED (7,9,19). The super-spreading event also occurred during the COVID-19 period. Before patient #31 was con rmed of having the infection in February 18, only 30 had con rmed COVID-19. However, the number of COVID-19 patients in North Gyeongsang Province (NGP) and Daegu dramatically increased after patient #31 visited Daenam Hospital in NGP and Shincheonji Church in Daegu before the infection was con rmed. On February 26, 1,146 patients were reported, exceeding 1,000 patients for the rst time (5,10). Because of the high infectivity of COVID-19 and possible infection from non-speci c people, EDs and hospitals are no longer considered as a safe place. Instead, they are considered as a hot zone (19,26). Therefore, non-emergency patients were thought to have fewer visits to the ED. The reduction in ED visits among non-emergency patients suggests an increase in admission rates and decrease in the number of alert patients visiting the ED.
In Korea, the incidence of in uenza showed bimodal patterns during winter and spring. In our study, the number of in uenza cases decreased since February during the COVID-19 period. Similarly, Noh et al. reported that in uenza rarely occurred during the spring of 2020 (27). During the COVID-19 period, the number of individuals wearing mask increased, and hand hygiene practices improved (27,28). These behaviors were thought to have helped prevent in uenza. In our study, the number of sepsis patients increased since February during the COVID-19 period. This nding is possibly because of the overall decrease in the proportion of non-emergency patients. Because many people stay at home and are not performing any outdoor activities because of fear of acquiring COVID-19, the number of patients visiting the ED because of trauma has decreased (28).
Some studies showed a difference in the number of patients and severity of the condition of patients visiting the ED according to the daily cycle (21,25). In our study, we also showed that the overall number of patients visiting the ED decreased after the super-spreading event occurred during the COVID-19 period compared to the pre-COVID-19 period. Moreover, at night time, the decrease was lesser than other times. This relatively less reduction in the number of COVID-19 cases at night may be because of the fact that there is no other place where the patient can be treated during this time of the day.
This study has the following limitations. First, only three university hospitals in Seoul and Gyeonggi Province were involved. Hence, our results do not re ect the statistics of all ED patients in Korea. Second, only one primary diagnosis was recorded; it does not involve all accompanying diagnoses. In some cases, the sub-diagnosis is important. However, in the ED, the patient is classi ed mainly according to their primary diagnosis. This study only analyzed the overall trend; hence, it would not have signi cantly affected our results.
In conclusion, this study showed changes in the patterns of ED visits during the COVID-19 outbreak. During this period, the total number of patients and non-emergency patients visiting the ED decreased. However, the COVID-19 outbreak still persists. Further research is needed to determine whether these results will remain the same or will change because of the characteristics of local EDs.

Declarations Ethics approval and consent to participate
The study protocol is performed in accordance with the relevant guidelines. The requirement for informed consent was waived by Institutional Review Board of Korea University. Because this is a retrospective observational study and the data was extracted without identifying the study participants' personal information, informed consent was not sought for the present study. This study was reviewed and approved by the Institutional Review Board of Korea University. (IRB no.: 2020GR0208).

Consent for publication Not Applicable
Availability of data and materials The datasets generated and/or analyzed during the current study are not publicly available due to our IRB approval that the patient's data can only be used for this study and reuse is not allowed but are available from the corresponding author on reasonable request.

Competing interests
The authors declare that they have no competing interests.