TY - JOUR
AU - Ro, Young, Sun
AB - Abstract Background Snakebite is a global public health crisis, but there are no nationwide data on snakebite in South Korea. The aim of this study was to describe the epidemiological profile and outcomes of snakebite cases in South Korea seasonally. Methods The selected subjects were patients of all ages with a chief complaint of snakebite who presented to participating emergency departments (EDs) between 1 January 2011 and 31 December 2016. Results A total of 1335 patients were eligible for the study. There were an average of 223 snakebite cases reported each year. Most snakebites occurred during the summer months (55.9%) in patients aged 40–59 y (36.3%) and males (61.5%). Snakebites occurred most frequently on Mondays (22.9%) between 12:00 and 17:59 h (42.0%) outdoors (57.9%) and in farm areas (20.7%). Over 82% of the bites were by venomous snakes across all seasons, and 66% of the patients visited EDs without using emergency medical services. Based on the excess mortality ratio-adjusted injury severity score, 88, 9.2 and 2.8% had mild, moderate and severe injuries, respectively. There were 10 fatalities during the study period. Conclusion This study provides essential information to understand and assess the burden and distribution of snakebites in South Korea and provides valuable information for developing appropriate prevention and control interventions to address it. envenomation, epidemiology, Gloydius, Rhabdophis, snakebites Introduction Snakebite is a major global public health problem in both tropical developing countries1 and in developed countries.2 An estimated 4.5 to 5.4 million snakebites occur worldwide each year, resulting in 1.8 to 2.7 million cases of envenomation and total deaths ranging from 81 000 to 138 000 every year.3 In addition, a large number of snakebite victims survive with permanent physical sequelae due to tissue necrosis, spat venom-ophthalmia, persistent nerve damage, as well as long-term psychological consequences including post-traumatic stress disorder and depression.3,4 The burden of snakebite is clear, yet it has been largely neglected by the global health community. Given the extent of the global burden of snakebite, WHO reinstated snakebite under the category of ‘neglected tropical diseases’ in 2017.5 Snakebite is a known issue in South Korea6 but there have been no previous attempts to gather accurate statistics on its incidence, clinical profile and mortality nationwide. A total of 16 species of snakes are known to reside in South Korea, four of which are venomous snakes: Gloydius brevicaudus, Gloydius ussuriensis, Gloydius intermedius and Rhabdophis tigrinus.7,8 While the case fatality rate in snakebite envenomation is low in South Korea, a substantial number of snakebite injuries may occur annually. Previous studies in other Asian countries have reported seasonal variations in snakebite incidence and mortality; the highest incidence and case fatality rates in these studies were reported during the peak of the monsoon or rainy season.9,10 There is currently a lack of information on the epidemiology of snakebites in South Korea. Most studies available for snakebites in South Korea are fragmented and use single hospital-based data and thus are not representative of the situation nationwide.7,11 Current understanding of envenomation pathophysiology, the best practices for treatment and the factors that contribute to morbidity and mortality are incomplete. Moreover, no previous studies have examined seasonal variations in epidemiology and clinical outcomes of snakebites in South Korea. The aim of this study was to describe the epidemiology and outcomes of snakebite cases in South Korea based on season by using a nationally representative database, the Emergency Department-based Injury In-depth Surveillance (EDIIS). Materials and methods Study design and setting and data source This study was a cross-sectional study using cases registered in the EDIIS. The EDIIS is a nationwide prospective clinical database of injured patients visiting emergency departments (EDs) that has supported the Korea Centers for Disease Control and Prevention (KCDC) since 2006.12 The EDIIS data source design was based on the International Classification of External Causes of Injury (ICECI)-WHO core data set. The variables are categorised by patients’ demographic data, injury-related information, prehospital care, clinical findings, diagnosis, treatment, ED disposition and outcomes. In 2006, five EDs participated and there are currently 23 EDs participating in EDIIS nationwide (Figure 1). All of the EDIIS- participating EDs are located in tertiary, university-affiliated hospitals. The surveillance and data collection are performed by general physicians and supervised by emergency physicians. Trained research coordinators monitor the activity on a daily basis and input the data to the online database system of the KCDC. The Data Management Committee provides audits and quality feedback on a monthly basis. Figure 1. Open in new tabDownload slide Study population. Figure 1. Open in new tabDownload slide Study population. In South Korea, the ED levels are designated by the government as levels 1 to 3 based on ED characteristics including human resources, essential equipment, level of service and size of department. Most level 3 EDs are operated by general physicians and provide basic emergency care. In accordance with the law, emergency physicians are prepared 24 h per day and provide advanced emergency care services in level 1 or 2 EDs. There are 36 level 1 EDs, and approximately 117 level 2 and 258 level 3 EDs in South Korea, and they all are re-evaluated annually.13 Of the 23 EDIIS-participating EDs, 13 are level 1 and 10 are level 2. Study population The study population included patients of all ages who visited EDIIS-participating EDs for snakebites from 1 January 2011 to 31 December 2016. Snakebite patients were defined as those with a mechanism of injury as ‘snakebite (C2.43)’ in EDIIS. Patients missing clinical outcome (ED and hospital disposition and injury severity) or season of injury data were excluded. Data variables The variables considered in this study include: (1) patients’ demographic factors, including age, gender and occupation (only collected from hospitalised patients); (2) injury-related factors, including year of injury, day of injury, time of injury, emergency medical service (EMS) area, place of injury, activity at the time of injury, intention and body part injured; and (3) prehospital and hospital factors, including mode of transport, time of ED arrival and surgical status (Yes/No). We also examined clinical outcomes of snakebite patients, including clinically important injury, overall hospital mortality and injury severity. Clinically important injuries were defined as snakebite injuries that require hospital admission, emergency inter-hospital transportation and/or result in death in EDs. Overall hospital mortality was defined as death that occurred in the ED or hospital ward. Snakebite injury severity was classified according to the excess mortality ratio-adjusted injury severity score (EMR-ISS), an injury severity scoring system based on ICD-10, which is similar to the new ISS (NISS) calculated from the abbreviated injury scale.14 Scores of 1 to 3 were classified as mild, 4 to 8 as moderate and 9 to 75 as severe snakebite injury. Statistical analysis Snakebite patients were divided into three groups according to the season during which snakebites occurred: spring (March–May), summer (June–August) and autumn/winter (September–February). Autumn and winter were combined into a single group because of the small number of snakebite cases that occurred in those months. The continuous variables were described as mean and SD for normal distribution and median and IQR for non-normal distribution. The categorical variables were described as frequency and percentage and χ2 test was used. SAS software version 9.4 (SAS institute Inc., Cary, NC, USA) was used for all statistical analysis; p<0.05 was considered statistically significant. Results Demographic factors of snakebite cases We identified a total of 1335 patients in EDIIS-participating EDs from January 2011 to December 2016 for our final analysis (Figure 2). Of the total snakebite cases, 211 (15.8%) occurred during spring, 746 (55.9%) during summer and 378 (28.3%) during the autumn/winter season. During the study period, the incidence of snakebite remained fairly consistent, ranging from 200–247 annually with an average of 223 bites per year. The most reported cases were from six EDs in the Gyeonggi province EMS area, two EDs in the Gwangju city EMS area and one ED in the Jeollabuk province EMS area. Figure 2. Open in new tabDownload slide Map of South Korea by provinces and number of EDIIS participating hospitals. Figure 2. Open in new tabDownload slide Map of South Korea by provinces and number of EDIIS participating hospitals. Demographic characteristics are described in Table 1. The majority of snakebite patients were in the age groups of 40–59 y (36.3%) and 60–79 y (35.8%) and were male (61.5%). Among 779 admitted patients, 165 (21.2%) of them worked in the agricultural, forestry or fishery sectors. Demographic characteristics of snakebite patients in the ED, including age, gender and occupation showed a statistically significant difference based on the seasons (p<0.01 for all). Snakebite patients who presented during the spring were more likely to be older (41.2% in the 60–79 y age group) and female (57.8%) compared with those who presented during summer (34.9% in the 60–79 y age group and 35.5% female) or autumn/winter (34.7% in the 60–79 y age group and 33.6% female). Table 1. Patient factors based on season in snakebite victims Variables Total N (%) Season* p-value Spring Summer Autumn/winter N (%) N (%) N (%) Total 1335 (100) 211 (15.8) 746 (55.9) 378 (28.3) Age (y) <0.01  Child (0–19) 147 (11.0) 14 (6.6) 89 (11.9) 44 (11.6)  Adulthood (20–39) 169 (12.7) 13 (6.2) 107 (14.3) 49 (13.0)  Middle adulthood (40–59) 485 (36.3) 77 (36.5) 268 (35.9) 140 (37.0)  Later adulthood (60–79) 478 (35.8) 87 (41.2) 260 (34.9) 131 (34.7)  Elderly (80+) 56 (4.2) 20 (9.5) 22 (2.9) 14 (3.7) Gender <0.01  Male 821 (61.5) 89 (42.2) 481 (64.5) 251 (66.4)  Female 514 (38.5) 122 (57.8) 265 (35.5) 127 (33.6) Occupation† <0.01  Agricultural, forestry, fishery 165 (21.2) 24 (18.6) 103 (23.8) 38 (17.5)  Soldier 6 (0.8) 1 (0.8) 4 (0.9) 1 (0.5)  Student 67 (8.6) 5 (3.9) 40 (9.2) 22 (10.1)  Homemaker 72 (9.2) 23 (17.8) 32 (7.4) 17 (7.8)  Unemployed 139 (17.8) 29 (22.5) 61 (14.1) 49 (22.6)  Office (admin, expert, specialist) 78 (10.1) 11(8.5) 48(11.1) 19 (8.8)  Production, sales and services worker 83 (10.6) 16 (12.4) 41 (9.5) 26 (12.0)  Other 25 (3.2) 1 (0.8) 22 (5.1) 2 (0.9)  Unknown 144 (18.5) 19 (14.7) 82 (18.9) 43 (19.8) Variables Total N (%) Season* p-value Spring Summer Autumn/winter N (%) N (%) N (%) Total 1335 (100) 211 (15.8) 746 (55.9) 378 (28.3) Age (y) <0.01  Child (0–19) 147 (11.0) 14 (6.6) 89 (11.9) 44 (11.6)  Adulthood (20–39) 169 (12.7) 13 (6.2) 107 (14.3) 49 (13.0)  Middle adulthood (40–59) 485 (36.3) 77 (36.5) 268 (35.9) 140 (37.0)  Later adulthood (60–79) 478 (35.8) 87 (41.2) 260 (34.9) 131 (34.7)  Elderly (80+) 56 (4.2) 20 (9.5) 22 (2.9) 14 (3.7) Gender <0.01  Male 821 (61.5) 89 (42.2) 481 (64.5) 251 (66.4)  Female 514 (38.5) 122 (57.8) 265 (35.5) 127 (33.6) Occupation† <0.01  Agricultural, forestry, fishery 165 (21.2) 24 (18.6) 103 (23.8) 38 (17.5)  Soldier 6 (0.8) 1 (0.8) 4 (0.9) 1 (0.5)  Student 67 (8.6) 5 (3.9) 40 (9.2) 22 (10.1)  Homemaker 72 (9.2) 23 (17.8) 32 (7.4) 17 (7.8)  Unemployed 139 (17.8) 29 (22.5) 61 (14.1) 49 (22.6)  Office (admin, expert, specialist) 78 (10.1) 11(8.5) 48(11.1) 19 (8.8)  Production, sales and services worker 83 (10.6) 16 (12.4) 41 (9.5) 26 (12.0)  Other 25 (3.2) 1 (0.8) 22 (5.1) 2 (0.9)  Unknown 144 (18.5) 19 (14.7) 82 (18.9) 43 (19.8) *spring: March–May; summer: June–August; autumn/winter: September–February. †Information on occupation was collected from hospital-admitted patients only (n=779). Open in new tab Table 1. Patient factors based on season in snakebite victims Variables Total N (%) Season* p-value Spring Summer Autumn/winter N (%) N (%) N (%) Total 1335 (100) 211 (15.8) 746 (55.9) 378 (28.3) Age (y) <0.01  Child (0–19) 147 (11.0) 14 (6.6) 89 (11.9) 44 (11.6)  Adulthood (20–39) 169 (12.7) 13 (6.2) 107 (14.3) 49 (13.0)  Middle adulthood (40–59) 485 (36.3) 77 (36.5) 268 (35.9) 140 (37.0)  Later adulthood (60–79) 478 (35.8) 87 (41.2) 260 (34.9) 131 (34.7)  Elderly (80+) 56 (4.2) 20 (9.5) 22 (2.9) 14 (3.7) Gender <0.01  Male 821 (61.5) 89 (42.2) 481 (64.5) 251 (66.4)  Female 514 (38.5) 122 (57.8) 265 (35.5) 127 (33.6) Occupation† <0.01  Agricultural, forestry, fishery 165 (21.2) 24 (18.6) 103 (23.8) 38 (17.5)  Soldier 6 (0.8) 1 (0.8) 4 (0.9) 1 (0.5)  Student 67 (8.6) 5 (3.9) 40 (9.2) 22 (10.1)  Homemaker 72 (9.2) 23 (17.8) 32 (7.4) 17 (7.8)  Unemployed 139 (17.8) 29 (22.5) 61 (14.1) 49 (22.6)  Office (admin, expert, specialist) 78 (10.1) 11(8.5) 48(11.1) 19 (8.8)  Production, sales and services worker 83 (10.6) 16 (12.4) 41 (9.5) 26 (12.0)  Other 25 (3.2) 1 (0.8) 22 (5.1) 2 (0.9)  Unknown 144 (18.5) 19 (14.7) 82 (18.9) 43 (19.8) Variables Total N (%) Season* p-value Spring Summer Autumn/winter N (%) N (%) N (%) Total 1335 (100) 211 (15.8) 746 (55.9) 378 (28.3) Age (y) <0.01  Child (0–19) 147 (11.0) 14 (6.6) 89 (11.9) 44 (11.6)  Adulthood (20–39) 169 (12.7) 13 (6.2) 107 (14.3) 49 (13.0)  Middle adulthood (40–59) 485 (36.3) 77 (36.5) 268 (35.9) 140 (37.0)  Later adulthood (60–79) 478 (35.8) 87 (41.2) 260 (34.9) 131 (34.7)  Elderly (80+) 56 (4.2) 20 (9.5) 22 (2.9) 14 (3.7) Gender <0.01  Male 821 (61.5) 89 (42.2) 481 (64.5) 251 (66.4)  Female 514 (38.5) 122 (57.8) 265 (35.5) 127 (33.6) Occupation† <0.01  Agricultural, forestry, fishery 165 (21.2) 24 (18.6) 103 (23.8) 38 (17.5)  Soldier 6 (0.8) 1 (0.8) 4 (0.9) 1 (0.5)  Student 67 (8.6) 5 (3.9) 40 (9.2) 22 (10.1)  Homemaker 72 (9.2) 23 (17.8) 32 (7.4) 17 (7.8)  Unemployed 139 (17.8) 29 (22.5) 61 (14.1) 49 (22.6)  Office (admin, expert, specialist) 78 (10.1) 11(8.5) 48(11.1) 19 (8.8)  Production, sales and services worker 83 (10.6) 16 (12.4) 41 (9.5) 26 (12.0)  Other 25 (3.2) 1 (0.8) 22 (5.1) 2 (0.9)  Unknown 144 (18.5) 19 (14.7) 82 (18.9) 43 (19.8) *spring: March–May; summer: June–August; autumn/winter: September–February. †Information on occupation was collected from hospital-admitted patients only (n=779). Open in new tab Injury-related factors of snakebite cases The injury-related factors are described in Table 2. Most of the injuries occurred on Mondays (22.9%) and Sundays (17.2%) and during daytime between noon and 17:59 h (42%). The highest snakebite incidence occurred in the Gyeonggi EMS area with 226 cases (17%) followed by Gwangju with 215 cases (16.1%). However, during spring, the highest incidence occurred in Gwangju (23.7%). During summer, the Gangwon EMS area presented the highest percentage of snakebite cases (17.7%). The majority of the snakebites occurred outdoors (57.9%) and 20.7% were in farm areas. For those snakebite cases that occurred in outdoor areas, the highest incidence was observed during spring (64.5% vs 55.6% for summer and 58.7% for autumn/winter) and for those that occurred in farm areas, the highest incidence was observed during summer (22.8% vs 18.5% for spring and 17.7% for autumn/winter). Most of the snakebites occurred while working (37.0%) followed by during leisure activities (31.7%). However, during the autumn/winter season, injury most frequently occurred during leisure activities (33.6%). All of the snakebite cases (except for one) were unintentional injuries. Table 2. Injury factors based on season in snakebite victims Variables Total Season* p-value N (%) Spring Summer Autumn/winter N (%) N (%) N (%) Total 1335 (100) 211 (15.8) 746 (55.9) 378 (28.3) Year of injury 0.02  2011 200 (15.0) 31 (14.7) 101 (13.5) 68 (18.0)  2012 212 (15.8) 34 (16.1) 129 (17.3) 49 (13.0)  2013 247 (18.5) 43 (20.4) 144 (19.3) 60 (15.9)  2014 218 (16.3) 24 (11.4) 113 (15.2) 81 (21.4)  2015 229 (17.2) 34 (16.1) 130 (17.4) 65 (17.2)  2016 229 (17.2) 45 (21.3) 129 (17.3) 55 (14.6) Day of injury 0.01  Monday 306 (22.9) 52 (24.6) 176 (23.6) 78 (20.6)  Tuesday 185 (13.9) 28 (13.3) 102 (13.7) 55 (14.6)  Wednesday 140 (10.5) 22 (10.4) 72 (9.7) 46 (12.2)  Thursday 158 (11.8) 21 (10.0) 94 (12.6) 43 (11.4)  Friday 149 (11.2) 20 (9.5) 77 (10.3) 52 (13.8)  Saturday 167 (12.5) 26 (12.3) 91 (12.2) 50 (13.2)  Sunday 230 (17.2) 42 (19.9) 134 (18.0) 54 (14.3) Time of injury <0.01  00:00 to 05:59 75 (5.6) 7 (3.3) 51 (6.8) 17 (4.5)  06:00 to 11:59 378 (28.3) 69 (32.7) 208 (27.9) 101 (26.7)  12:00 to 17:59 561 (42.0) 113 (53.5) 270 (36.2) 178 (47.1)  18:00 to 23:59 321 (24.0) 22 (10.4) 217 (29.1) 82 (21.7) Emergency services area <0.01  Seoul 113 (8.5) 21 (10.0) 56 (7.5) 36 (9.5)  Busan 24 (1.8) 7 (3.3) 10 (1.3) 7 (1.9)  Daegu 6 (0.5) 1 (0.5) 2 (0.3) 3 (0.8)  Gangwon 197 (14.8) 16 (7.6) 132 (17.7) 49 (13.0)  Gyeonggi 226 (17.0) 33 (15.6) 128 (17.2) 65 (17.2)  Gyeongsangnam 121 (9.1) 14 (6.6) 66 (8.9) 41 (10.9)  Gwangju 215 (16.1) 50 (23.7) 116 (15.6) 49 (13.0)  Incheon 58 (4.3) 11 (5.2) 28 (3.8) 19 (5.0)  Jeju 47 (3.5) 6 (2.8) 20 (2.7) 21 (5.6)  Jeolla 211 (15.8) 31 (14.7) 120 (16.1) 60 (15.9)  Ulsan 51 (3.8) 15 (7.1) 25 (3.4) 11 (2.9)  Chungbuk 66 (4.9) 6 (2.9) 43 (5.8) 17 (4.5) Area type <0.01  Urban 113 (8.5) 21 (10.0) 56 (7.5) 36 (9.5)  Suburban 354 (26.5) 84 (39.8) 181 (24.3) 89 (23.5)  Rural 868 (65.0) 106 (50.2) 509 (68.2) 253 (66.9) Place of injury  Farm area 276 (20.7) 39 (18.5) 170 (22.8) 67 (17.7) 0.21  Industrial area 5 (0.4) 2 (1.0) 2 (0.3) 1 (0.3)  Leisure area 58 (4.3) 9 (4.3) 32 (4.3) 17 (4.5)  Outdoor area 773 (57.9) 136 (64.5) 415 (55.6) 222 (58.7)  Public building 12 (0.9) 1 (0.5) 4 (0.5) 7 (1.9)  Residential area 142 (10.6) 15 (7.1) 85 (11.4) 42 (11.1)  Other 1 (0.1) 0 (0) 1 (0.1) 0 (0)  Unknown 68 (5.1) 9 (4.3) 37 (5.0) 22 (5.8) Activity during injury <0.01  Working 494 (37.0) 77 (36.5) 292 (39.1) 125 (33.1)  Basic service 33 (2.5) 7 (3.32) 12 (1.6) 14 (3.7)  Daily living activity 323 (24.1) 54 (25.6) 172 (23.1) 97 (25.6)  Leisure activity 423 (31.7) 68 (32.2) 228 (30.6) 127 (33.6)  Travelling 20 (1.5) 1 (0.5) 19 (2.6) 0 (0)  Unknown 42 (3.2) 4 (1.9) 23 (3.1) 15 (4.0) Injury intention 0.51  Intentional 1 (0.1) 0 (0) 0 (0) 1(0.3)  Unintentional 1333 (99.8) 211 (100) 745 (99.9) 377 (99.7)  Unknown 1 (0.1) 0 (0) 1 (0.1) 0 (0) Body part injured 0.17  Head 8 (0.6) 0 (0) 8 (1.1) 0 (0)  Upper limb 77 (5.8) 13 (6.2) 41 (5.5) 23 (6.1)  Lower limb 43 (3.2) 5 (2.4) 29 (3.9) 9 (2.4)  Skin 1207 (90.4) 193 (91.5) 668 (89.5) 346 (91.5) Variables Total Season* p-value N (%) Spring Summer Autumn/winter N (%) N (%) N (%) Total 1335 (100) 211 (15.8) 746 (55.9) 378 (28.3) Year of injury 0.02  2011 200 (15.0) 31 (14.7) 101 (13.5) 68 (18.0)  2012 212 (15.8) 34 (16.1) 129 (17.3) 49 (13.0)  2013 247 (18.5) 43 (20.4) 144 (19.3) 60 (15.9)  2014 218 (16.3) 24 (11.4) 113 (15.2) 81 (21.4)  2015 229 (17.2) 34 (16.1) 130 (17.4) 65 (17.2)  2016 229 (17.2) 45 (21.3) 129 (17.3) 55 (14.6) Day of injury 0.01  Monday 306 (22.9) 52 (24.6) 176 (23.6) 78 (20.6)  Tuesday 185 (13.9) 28 (13.3) 102 (13.7) 55 (14.6)  Wednesday 140 (10.5) 22 (10.4) 72 (9.7) 46 (12.2)  Thursday 158 (11.8) 21 (10.0) 94 (12.6) 43 (11.4)  Friday 149 (11.2) 20 (9.5) 77 (10.3) 52 (13.8)  Saturday 167 (12.5) 26 (12.3) 91 (12.2) 50 (13.2)  Sunday 230 (17.2) 42 (19.9) 134 (18.0) 54 (14.3) Time of injury <0.01  00:00 to 05:59 75 (5.6) 7 (3.3) 51 (6.8) 17 (4.5)  06:00 to 11:59 378 (28.3) 69 (32.7) 208 (27.9) 101 (26.7)  12:00 to 17:59 561 (42.0) 113 (53.5) 270 (36.2) 178 (47.1)  18:00 to 23:59 321 (24.0) 22 (10.4) 217 (29.1) 82 (21.7) Emergency services area <0.01  Seoul 113 (8.5) 21 (10.0) 56 (7.5) 36 (9.5)  Busan 24 (1.8) 7 (3.3) 10 (1.3) 7 (1.9)  Daegu 6 (0.5) 1 (0.5) 2 (0.3) 3 (0.8)  Gangwon 197 (14.8) 16 (7.6) 132 (17.7) 49 (13.0)  Gyeonggi 226 (17.0) 33 (15.6) 128 (17.2) 65 (17.2)  Gyeongsangnam 121 (9.1) 14 (6.6) 66 (8.9) 41 (10.9)  Gwangju 215 (16.1) 50 (23.7) 116 (15.6) 49 (13.0)  Incheon 58 (4.3) 11 (5.2) 28 (3.8) 19 (5.0)  Jeju 47 (3.5) 6 (2.8) 20 (2.7) 21 (5.6)  Jeolla 211 (15.8) 31 (14.7) 120 (16.1) 60 (15.9)  Ulsan 51 (3.8) 15 (7.1) 25 (3.4) 11 (2.9)  Chungbuk 66 (4.9) 6 (2.9) 43 (5.8) 17 (4.5) Area type <0.01  Urban 113 (8.5) 21 (10.0) 56 (7.5) 36 (9.5)  Suburban 354 (26.5) 84 (39.8) 181 (24.3) 89 (23.5)  Rural 868 (65.0) 106 (50.2) 509 (68.2) 253 (66.9) Place of injury  Farm area 276 (20.7) 39 (18.5) 170 (22.8) 67 (17.7) 0.21  Industrial area 5 (0.4) 2 (1.0) 2 (0.3) 1 (0.3)  Leisure area 58 (4.3) 9 (4.3) 32 (4.3) 17 (4.5)  Outdoor area 773 (57.9) 136 (64.5) 415 (55.6) 222 (58.7)  Public building 12 (0.9) 1 (0.5) 4 (0.5) 7 (1.9)  Residential area 142 (10.6) 15 (7.1) 85 (11.4) 42 (11.1)  Other 1 (0.1) 0 (0) 1 (0.1) 0 (0)  Unknown 68 (5.1) 9 (4.3) 37 (5.0) 22 (5.8) Activity during injury <0.01  Working 494 (37.0) 77 (36.5) 292 (39.1) 125 (33.1)  Basic service 33 (2.5) 7 (3.32) 12 (1.6) 14 (3.7)  Daily living activity 323 (24.1) 54 (25.6) 172 (23.1) 97 (25.6)  Leisure activity 423 (31.7) 68 (32.2) 228 (30.6) 127 (33.6)  Travelling 20 (1.5) 1 (0.5) 19 (2.6) 0 (0)  Unknown 42 (3.2) 4 (1.9) 23 (3.1) 15 (4.0) Injury intention 0.51  Intentional 1 (0.1) 0 (0) 0 (0) 1(0.3)  Unintentional 1333 (99.8) 211 (100) 745 (99.9) 377 (99.7)  Unknown 1 (0.1) 0 (0) 1 (0.1) 0 (0) Body part injured 0.17  Head 8 (0.6) 0 (0) 8 (1.1) 0 (0)  Upper limb 77 (5.8) 13 (6.2) 41 (5.5) 23 (6.1)  Lower limb 43 (3.2) 5 (2.4) 29 (3.9) 9 (2.4)  Skin 1207 (90.4) 193 (91.5) 668 (89.5) 346 (91.5) *spring: March–May; summer: June–August; autumn/winter: September–February. Open in new tab Table 2. Injury factors based on season in snakebite victims Variables Total Season* p-value N (%) Spring Summer Autumn/winter N (%) N (%) N (%) Total 1335 (100) 211 (15.8) 746 (55.9) 378 (28.3) Year of injury 0.02  2011 200 (15.0) 31 (14.7) 101 (13.5) 68 (18.0)  2012 212 (15.8) 34 (16.1) 129 (17.3) 49 (13.0)  2013 247 (18.5) 43 (20.4) 144 (19.3) 60 (15.9)  2014 218 (16.3) 24 (11.4) 113 (15.2) 81 (21.4)  2015 229 (17.2) 34 (16.1) 130 (17.4) 65 (17.2)  2016 229 (17.2) 45 (21.3) 129 (17.3) 55 (14.6) Day of injury 0.01  Monday 306 (22.9) 52 (24.6) 176 (23.6) 78 (20.6)  Tuesday 185 (13.9) 28 (13.3) 102 (13.7) 55 (14.6)  Wednesday 140 (10.5) 22 (10.4) 72 (9.7) 46 (12.2)  Thursday 158 (11.8) 21 (10.0) 94 (12.6) 43 (11.4)  Friday 149 (11.2) 20 (9.5) 77 (10.3) 52 (13.8)  Saturday 167 (12.5) 26 (12.3) 91 (12.2) 50 (13.2)  Sunday 230 (17.2) 42 (19.9) 134 (18.0) 54 (14.3) Time of injury <0.01  00:00 to 05:59 75 (5.6) 7 (3.3) 51 (6.8) 17 (4.5)  06:00 to 11:59 378 (28.3) 69 (32.7) 208 (27.9) 101 (26.7)  12:00 to 17:59 561 (42.0) 113 (53.5) 270 (36.2) 178 (47.1)  18:00 to 23:59 321 (24.0) 22 (10.4) 217 (29.1) 82 (21.7) Emergency services area <0.01  Seoul 113 (8.5) 21 (10.0) 56 (7.5) 36 (9.5)  Busan 24 (1.8) 7 (3.3) 10 (1.3) 7 (1.9)  Daegu 6 (0.5) 1 (0.5) 2 (0.3) 3 (0.8)  Gangwon 197 (14.8) 16 (7.6) 132 (17.7) 49 (13.0)  Gyeonggi 226 (17.0) 33 (15.6) 128 (17.2) 65 (17.2)  Gyeongsangnam 121 (9.1) 14 (6.6) 66 (8.9) 41 (10.9)  Gwangju 215 (16.1) 50 (23.7) 116 (15.6) 49 (13.0)  Incheon 58 (4.3) 11 (5.2) 28 (3.8) 19 (5.0)  Jeju 47 (3.5) 6 (2.8) 20 (2.7) 21 (5.6)  Jeolla 211 (15.8) 31 (14.7) 120 (16.1) 60 (15.9)  Ulsan 51 (3.8) 15 (7.1) 25 (3.4) 11 (2.9)  Chungbuk 66 (4.9) 6 (2.9) 43 (5.8) 17 (4.5) Area type <0.01  Urban 113 (8.5) 21 (10.0) 56 (7.5) 36 (9.5)  Suburban 354 (26.5) 84 (39.8) 181 (24.3) 89 (23.5)  Rural 868 (65.0) 106 (50.2) 509 (68.2) 253 (66.9) Place of injury  Farm area 276 (20.7) 39 (18.5) 170 (22.8) 67 (17.7) 0.21  Industrial area 5 (0.4) 2 (1.0) 2 (0.3) 1 (0.3)  Leisure area 58 (4.3) 9 (4.3) 32 (4.3) 17 (4.5)  Outdoor area 773 (57.9) 136 (64.5) 415 (55.6) 222 (58.7)  Public building 12 (0.9) 1 (0.5) 4 (0.5) 7 (1.9)  Residential area 142 (10.6) 15 (7.1) 85 (11.4) 42 (11.1)  Other 1 (0.1) 0 (0) 1 (0.1) 0 (0)  Unknown 68 (5.1) 9 (4.3) 37 (5.0) 22 (5.8) Activity during injury <0.01  Working 494 (37.0) 77 (36.5) 292 (39.1) 125 (33.1)  Basic service 33 (2.5) 7 (3.32) 12 (1.6) 14 (3.7)  Daily living activity 323 (24.1) 54 (25.6) 172 (23.1) 97 (25.6)  Leisure activity 423 (31.7) 68 (32.2) 228 (30.6) 127 (33.6)  Travelling 20 (1.5) 1 (0.5) 19 (2.6) 0 (0)  Unknown 42 (3.2) 4 (1.9) 23 (3.1) 15 (4.0) Injury intention 0.51  Intentional 1 (0.1) 0 (0) 0 (0) 1(0.3)  Unintentional 1333 (99.8) 211 (100) 745 (99.9) 377 (99.7)  Unknown 1 (0.1) 0 (0) 1 (0.1) 0 (0) Body part injured 0.17  Head 8 (0.6) 0 (0) 8 (1.1) 0 (0)  Upper limb 77 (5.8) 13 (6.2) 41 (5.5) 23 (6.1)  Lower limb 43 (3.2) 5 (2.4) 29 (3.9) 9 (2.4)  Skin 1207 (90.4) 193 (91.5) 668 (89.5) 346 (91.5) Variables Total Season* p-value N (%) Spring Summer Autumn/winter N (%) N (%) N (%) Total 1335 (100) 211 (15.8) 746 (55.9) 378 (28.3) Year of injury 0.02  2011 200 (15.0) 31 (14.7) 101 (13.5) 68 (18.0)  2012 212 (15.8) 34 (16.1) 129 (17.3) 49 (13.0)  2013 247 (18.5) 43 (20.4) 144 (19.3) 60 (15.9)  2014 218 (16.3) 24 (11.4) 113 (15.2) 81 (21.4)  2015 229 (17.2) 34 (16.1) 130 (17.4) 65 (17.2)  2016 229 (17.2) 45 (21.3) 129 (17.3) 55 (14.6) Day of injury 0.01  Monday 306 (22.9) 52 (24.6) 176 (23.6) 78 (20.6)  Tuesday 185 (13.9) 28 (13.3) 102 (13.7) 55 (14.6)  Wednesday 140 (10.5) 22 (10.4) 72 (9.7) 46 (12.2)  Thursday 158 (11.8) 21 (10.0) 94 (12.6) 43 (11.4)  Friday 149 (11.2) 20 (9.5) 77 (10.3) 52 (13.8)  Saturday 167 (12.5) 26 (12.3) 91 (12.2) 50 (13.2)  Sunday 230 (17.2) 42 (19.9) 134 (18.0) 54 (14.3) Time of injury <0.01  00:00 to 05:59 75 (5.6) 7 (3.3) 51 (6.8) 17 (4.5)  06:00 to 11:59 378 (28.3) 69 (32.7) 208 (27.9) 101 (26.7)  12:00 to 17:59 561 (42.0) 113 (53.5) 270 (36.2) 178 (47.1)  18:00 to 23:59 321 (24.0) 22 (10.4) 217 (29.1) 82 (21.7) Emergency services area <0.01  Seoul 113 (8.5) 21 (10.0) 56 (7.5) 36 (9.5)  Busan 24 (1.8) 7 (3.3) 10 (1.3) 7 (1.9)  Daegu 6 (0.5) 1 (0.5) 2 (0.3) 3 (0.8)  Gangwon 197 (14.8) 16 (7.6) 132 (17.7) 49 (13.0)  Gyeonggi 226 (17.0) 33 (15.6) 128 (17.2) 65 (17.2)  Gyeongsangnam 121 (9.1) 14 (6.6) 66 (8.9) 41 (10.9)  Gwangju 215 (16.1) 50 (23.7) 116 (15.6) 49 (13.0)  Incheon 58 (4.3) 11 (5.2) 28 (3.8) 19 (5.0)  Jeju 47 (3.5) 6 (2.8) 20 (2.7) 21 (5.6)  Jeolla 211 (15.8) 31 (14.7) 120 (16.1) 60 (15.9)  Ulsan 51 (3.8) 15 (7.1) 25 (3.4) 11 (2.9)  Chungbuk 66 (4.9) 6 (2.9) 43 (5.8) 17 (4.5) Area type <0.01  Urban 113 (8.5) 21 (10.0) 56 (7.5) 36 (9.5)  Suburban 354 (26.5) 84 (39.8) 181 (24.3) 89 (23.5)  Rural 868 (65.0) 106 (50.2) 509 (68.2) 253 (66.9) Place of injury  Farm area 276 (20.7) 39 (18.5) 170 (22.8) 67 (17.7) 0.21  Industrial area 5 (0.4) 2 (1.0) 2 (0.3) 1 (0.3)  Leisure area 58 (4.3) 9 (4.3) 32 (4.3) 17 (4.5)  Outdoor area 773 (57.9) 136 (64.5) 415 (55.6) 222 (58.7)  Public building 12 (0.9) 1 (0.5) 4 (0.5) 7 (1.9)  Residential area 142 (10.6) 15 (7.1) 85 (11.4) 42 (11.1)  Other 1 (0.1) 0 (0) 1 (0.1) 0 (0)  Unknown 68 (5.1) 9 (4.3) 37 (5.0) 22 (5.8) Activity during injury <0.01  Working 494 (37.0) 77 (36.5) 292 (39.1) 125 (33.1)  Basic service 33 (2.5) 7 (3.32) 12 (1.6) 14 (3.7)  Daily living activity 323 (24.1) 54 (25.6) 172 (23.1) 97 (25.6)  Leisure activity 423 (31.7) 68 (32.2) 228 (30.6) 127 (33.6)  Travelling 20 (1.5) 1 (0.5) 19 (2.6) 0 (0)  Unknown 42 (3.2) 4 (1.9) 23 (3.1) 15 (4.0) Injury intention 0.51  Intentional 1 (0.1) 0 (0) 0 (0) 1(0.3)  Unintentional 1333 (99.8) 211 (100) 745 (99.9) 377 (99.7)  Unknown 1 (0.1) 0 (0) 1 (0.1) 0 (0) Body part injured 0.17  Head 8 (0.6) 0 (0) 8 (1.1) 0 (0)  Upper limb 77 (5.8) 13 (6.2) 41 (5.5) 23 (6.1)  Lower limb 43 (3.2) 5 (2.4) 29 (3.9) 9 (2.4)  Skin 1207 (90.4) 193 (91.5) 668 (89.5) 346 (91.5) *spring: March–May; summer: June–August; autumn/winter: September–February. Open in new tab Prehospital and hospital factors of snakebite cases Prehospital and hospital factors are described in Table 3. Over 81% of the bites were by venomous snakes across all seasons and the majority of the patients visited EDs by non-ambulance vehicles (65.6%). About 3.1% of patients underwent operations and the highest operation rate (5.2%) was in spring. Table 3. Prehospital and hospital factors based on season in snakebite victims Variables Total N (%) Season* p-value Spring Summer Autumn/winter N (%) N (%) N (%) Total 1335 (100) 211 (15.8) 746 (55.9) 378 (28.3) Type of snakebite 0.89  Venomous 1093 (81.9) 171 (81.0) 614 (82.3) 308 (81.5)  Non-venomous 242 (18.1) 40 (19.0) 132 (17.7) 70 (18.5) Transport method 0.24  911 ambulance 204 (15.3) 39 (18.5) 103 (13.8) 62 (16.4)  Other ambulance 179 (12.4) 18 (8.5) 108 (14.5) 53 (14.0)  Police car 2 (0.2) 0 (0) 1 (0.1) 1 (0.3)  Other transport 876 (65.6) 139 (65.9) 493 (66.1) 244 (64.6)  Walking 72 (5.4) 14 (6.6) 40 (5.4) 18 (4.8)  Other/unknown 2 (0.2) 1 (0.5) 1 (0.1) 0 (0) Time of arrival <0.01  00:00 to 05:59 89 (6.7) 6 (2.8) 63 (8.5) 20 (5.3)  06:00 to 11:59 293 (22.0) 37(17.5) 181 (24.3) 75 (19.8)  12:00 to 17:59 535 (40.1) 117 (55.5) 262 (35.1) 156 (41.3)  18:00 to 23:59 418 (31.3) 51 (24.2) 240 (32.2) 127 (33.6) Operation 0.09  Yes 42 (3.1) 11 (5.2) 25 (3.4) 6 (1.6)  No 619 (46.4) 102 (48.3) 348 (46.6) 169 (44.7)  Unknown/missing 674 (50.5) 98 (46.5) 373 (50.0) 203 (53.7) Variables Total N (%) Season* p-value Spring Summer Autumn/winter N (%) N (%) N (%) Total 1335 (100) 211 (15.8) 746 (55.9) 378 (28.3) Type of snakebite 0.89  Venomous 1093 (81.9) 171 (81.0) 614 (82.3) 308 (81.5)  Non-venomous 242 (18.1) 40 (19.0) 132 (17.7) 70 (18.5) Transport method 0.24  911 ambulance 204 (15.3) 39 (18.5) 103 (13.8) 62 (16.4)  Other ambulance 179 (12.4) 18 (8.5) 108 (14.5) 53 (14.0)  Police car 2 (0.2) 0 (0) 1 (0.1) 1 (0.3)  Other transport 876 (65.6) 139 (65.9) 493 (66.1) 244 (64.6)  Walking 72 (5.4) 14 (6.6) 40 (5.4) 18 (4.8)  Other/unknown 2 (0.2) 1 (0.5) 1 (0.1) 0 (0) Time of arrival <0.01  00:00 to 05:59 89 (6.7) 6 (2.8) 63 (8.5) 20 (5.3)  06:00 to 11:59 293 (22.0) 37(17.5) 181 (24.3) 75 (19.8)  12:00 to 17:59 535 (40.1) 117 (55.5) 262 (35.1) 156 (41.3)  18:00 to 23:59 418 (31.3) 51 (24.2) 240 (32.2) 127 (33.6) Operation 0.09  Yes 42 (3.1) 11 (5.2) 25 (3.4) 6 (1.6)  No 619 (46.4) 102 (48.3) 348 (46.6) 169 (44.7)  Unknown/missing 674 (50.5) 98 (46.5) 373 (50.0) 203 (53.7) *spring: March–May; summer: June–August; autumn/winter: September–February. Open in new tab Table 3. Prehospital and hospital factors based on season in snakebite victims Variables Total N (%) Season* p-value Spring Summer Autumn/winter N (%) N (%) N (%) Total 1335 (100) 211 (15.8) 746 (55.9) 378 (28.3) Type of snakebite 0.89  Venomous 1093 (81.9) 171 (81.0) 614 (82.3) 308 (81.5)  Non-venomous 242 (18.1) 40 (19.0) 132 (17.7) 70 (18.5) Transport method 0.24  911 ambulance 204 (15.3) 39 (18.5) 103 (13.8) 62 (16.4)  Other ambulance 179 (12.4) 18 (8.5) 108 (14.5) 53 (14.0)  Police car 2 (0.2) 0 (0) 1 (0.1) 1 (0.3)  Other transport 876 (65.6) 139 (65.9) 493 (66.1) 244 (64.6)  Walking 72 (5.4) 14 (6.6) 40 (5.4) 18 (4.8)  Other/unknown 2 (0.2) 1 (0.5) 1 (0.1) 0 (0) Time of arrival <0.01  00:00 to 05:59 89 (6.7) 6 (2.8) 63 (8.5) 20 (5.3)  06:00 to 11:59 293 (22.0) 37(17.5) 181 (24.3) 75 (19.8)  12:00 to 17:59 535 (40.1) 117 (55.5) 262 (35.1) 156 (41.3)  18:00 to 23:59 418 (31.3) 51 (24.2) 240 (32.2) 127 (33.6) Operation 0.09  Yes 42 (3.1) 11 (5.2) 25 (3.4) 6 (1.6)  No 619 (46.4) 102 (48.3) 348 (46.6) 169 (44.7)  Unknown/missing 674 (50.5) 98 (46.5) 373 (50.0) 203 (53.7) Variables Total N (%) Season* p-value Spring Summer Autumn/winter N (%) N (%) N (%) Total 1335 (100) 211 (15.8) 746 (55.9) 378 (28.3) Type of snakebite 0.89  Venomous 1093 (81.9) 171 (81.0) 614 (82.3) 308 (81.5)  Non-venomous 242 (18.1) 40 (19.0) 132 (17.7) 70 (18.5) Transport method 0.24  911 ambulance 204 (15.3) 39 (18.5) 103 (13.8) 62 (16.4)  Other ambulance 179 (12.4) 18 (8.5) 108 (14.5) 53 (14.0)  Police car 2 (0.2) 0 (0) 1 (0.1) 1 (0.3)  Other transport 876 (65.6) 139 (65.9) 493 (66.1) 244 (64.6)  Walking 72 (5.4) 14 (6.6) 40 (5.4) 18 (4.8)  Other/unknown 2 (0.2) 1 (0.5) 1 (0.1) 0 (0) Time of arrival <0.01  00:00 to 05:59 89 (6.7) 6 (2.8) 63 (8.5) 20 (5.3)  06:00 to 11:59 293 (22.0) 37(17.5) 181 (24.3) 75 (19.8)  12:00 to 17:59 535 (40.1) 117 (55.5) 262 (35.1) 156 (41.3)  18:00 to 23:59 418 (31.3) 51 (24.2) 240 (32.2) 127 (33.6) Operation 0.09  Yes 42 (3.1) 11 (5.2) 25 (3.4) 6 (1.6)  No 619 (46.4) 102 (48.3) 348 (46.6) 169 (44.7)  Unknown/missing 674 (50.5) 98 (46.5) 373 (50.0) 203 (53.7) *spring: March–May; summer: June–August; autumn/winter: September–February. Open in new tab Clinical outcomes of snakebite cases Clinical outcomes of snakebite cases are described in Table 4. Among 1335 snakebite patients, 33.3% were discharged from EDs, 54.5% were discharged after hospitalisation, 11.2% were transferred and 0.7% were dead. There were twice as many patients with clinically important injury (admitted, transferred or died in ED) than without clinically important injury (66.7 vs 33.3%). Based on the EMR-ISS, mild snakebite cases occurred most frequently (88.0%) with an EMR-ISS of <4. About 2.8% of the total snakebite cases were classified as severe cases with those occurring during summer showing the highest incidence of severe cases (3.4%). During the 6-y study period, there were 10 recorded fatalities due to snakebite (0.7%) and most of the mortality cases occurred in summer (8 cases). Table 4. Outcomes of snakebite patients based on season Variables Total N (%) Season* p-value Spring Summer Autumn/winter N (%) N (%) N (%) Total 1,335 (100) 211 (15.8) 746 (55.9) 378 (28.3) Clinical outcome 0.27  Discharged from ED 444 (33.3) 70 (33.2) 242 (32.5) 132 (34.9)  Discharged after hospitalisation 727 (54.5) 121 (57.3) 400 (53.6) 206 (54.5)  Transferred 150 (11.2) 19 (9.0) 95 (12.7) 36 (9.5)  Dead 10 (0.7) 1 (0.5) 8 (1.1) 1 (0.3)  Other/unknown 4 (0.3) 0 1 (0.1) 3 (0.8) Clinically important injury† 0.73  No 445 (33.3) 70 (33.2) 243 (32.6) 132 (34.9)  Yes 890 (66.7) 141 (66.8) 503 (67.4) 246 (65.1) Disease severity (EMR-ISS) 0.05  Mild (1–3) 1175 (88.0) 185 (87.7) 657 (88.1) 333 (88.1)  Moderate (4–8) 123 (9.2) 26 (12.3) 64 (8.6) 33 (8.7)  Severe (9–75) 37 (2.8) 0 (0) 25 (3.4) 12 (3.2) Overall mortality 0.29  Alive 1325 (99.3) 210 (99.5) 738 (98.9) 377 (99.7)  Dead 10 (0.8) 1 (0.5) 8 (1.1) 1 (0.3) Variables Total N (%) Season* p-value Spring Summer Autumn/winter N (%) N (%) N (%) Total 1,335 (100) 211 (15.8) 746 (55.9) 378 (28.3) Clinical outcome 0.27  Discharged from ED 444 (33.3) 70 (33.2) 242 (32.5) 132 (34.9)  Discharged after hospitalisation 727 (54.5) 121 (57.3) 400 (53.6) 206 (54.5)  Transferred 150 (11.2) 19 (9.0) 95 (12.7) 36 (9.5)  Dead 10 (0.7) 1 (0.5) 8 (1.1) 1 (0.3)  Other/unknown 4 (0.3) 0 1 (0.1) 3 (0.8) Clinically important injury† 0.73  No 445 (33.3) 70 (33.2) 243 (32.6) 132 (34.9)  Yes 890 (66.7) 141 (66.8) 503 (67.4) 246 (65.1) Disease severity (EMR-ISS) 0.05  Mild (1–3) 1175 (88.0) 185 (87.7) 657 (88.1) 333 (88.1)  Moderate (4–8) 123 (9.2) 26 (12.3) 64 (8.6) 33 (8.7)  Severe (9–75) 37 (2.8) 0 (0) 25 (3.4) 12 (3.2) Overall mortality 0.29  Alive 1325 (99.3) 210 (99.5) 738 (98.9) 377 (99.7)  Dead 10 (0.8) 1 (0.5) 8 (1.1) 1 (0.3) Abbreviations: ED: emergency department; EMR-ISS: excess mortality ratio-adjusted injury severity score. *spring: March–May; summer: June–August; autumn/winter: September–February. †clinically important injuries were defined as snakebite injuries that required hospital admission, emergency inter-hospital transportation and/or resulted in death in the emergency department. Open in new tab Table 4. Outcomes of snakebite patients based on season Variables Total N (%) Season* p-value Spring Summer Autumn/winter N (%) N (%) N (%) Total 1,335 (100) 211 (15.8) 746 (55.9) 378 (28.3) Clinical outcome 0.27  Discharged from ED 444 (33.3) 70 (33.2) 242 (32.5) 132 (34.9)  Discharged after hospitalisation 727 (54.5) 121 (57.3) 400 (53.6) 206 (54.5)  Transferred 150 (11.2) 19 (9.0) 95 (12.7) 36 (9.5)  Dead 10 (0.7) 1 (0.5) 8 (1.1) 1 (0.3)  Other/unknown 4 (0.3) 0 1 (0.1) 3 (0.8) Clinically important injury† 0.73  No 445 (33.3) 70 (33.2) 243 (32.6) 132 (34.9)  Yes 890 (66.7) 141 (66.8) 503 (67.4) 246 (65.1) Disease severity (EMR-ISS) 0.05  Mild (1–3) 1175 (88.0) 185 (87.7) 657 (88.1) 333 (88.1)  Moderate (4–8) 123 (9.2) 26 (12.3) 64 (8.6) 33 (8.7)  Severe (9–75) 37 (2.8) 0 (0) 25 (3.4) 12 (3.2) Overall mortality 0.29  Alive 1325 (99.3) 210 (99.5) 738 (98.9) 377 (99.7)  Dead 10 (0.8) 1 (0.5) 8 (1.1) 1 (0.3) Variables Total N (%) Season* p-value Spring Summer Autumn/winter N (%) N (%) N (%) Total 1,335 (100) 211 (15.8) 746 (55.9) 378 (28.3) Clinical outcome 0.27  Discharged from ED 444 (33.3) 70 (33.2) 242 (32.5) 132 (34.9)  Discharged after hospitalisation 727 (54.5) 121 (57.3) 400 (53.6) 206 (54.5)  Transferred 150 (11.2) 19 (9.0) 95 (12.7) 36 (9.5)  Dead 10 (0.7) 1 (0.5) 8 (1.1) 1 (0.3)  Other/unknown 4 (0.3) 0 1 (0.1) 3 (0.8) Clinically important injury† 0.73  No 445 (33.3) 70 (33.2) 243 (32.6) 132 (34.9)  Yes 890 (66.7) 141 (66.8) 503 (67.4) 246 (65.1) Disease severity (EMR-ISS) 0.05  Mild (1–3) 1175 (88.0) 185 (87.7) 657 (88.1) 333 (88.1)  Moderate (4–8) 123 (9.2) 26 (12.3) 64 (8.6) 33 (8.7)  Severe (9–75) 37 (2.8) 0 (0) 25 (3.4) 12 (3.2) Overall mortality 0.29  Alive 1325 (99.3) 210 (99.5) 738 (98.9) 377 (99.7)  Dead 10 (0.8) 1 (0.5) 8 (1.1) 1 (0.3) Abbreviations: ED: emergency department; EMR-ISS: excess mortality ratio-adjusted injury severity score. *spring: March–May; summer: June–August; autumn/winter: September–February. †clinically important injuries were defined as snakebite injuries that required hospital admission, emergency inter-hospital transportation and/or resulted in death in the emergency department. Open in new tab Discussion This study is the first epidemiological study of snakebite cases presenting to EDs in South Korea. During the study period (from 2011 to 2016), 1335 snakebite patients visited 23 EDIIS-participating EDs with the majority of cases occurring in summer. We also observed that the number of snakebite cases did not decrease over time, suggesting snakebite is an important public health issue in South Korea. Our analysis showed that season plays an important factor in the incidence and severity of snakebite cases in South Korea. The high number of snakebite cases during summer may be due to heavy rain during summer. This type of seasonal variation in snakebite incidence, particularly the high incidence during the monsoon or rainy season, has been previously reported.9,15 During heavy rain, holes and burrows fill with water and force snakes to emerge, which increases the overall incidence of snakebite cases.16 Moreover, snakes have a seasonal life cycle. During cold months, some snakes hibernate in pits as they lose their body temperature and their metabolisms decrease. When temperatures rise in summer they return to their natural environment and their metabolisms are restored to normal levels.17 Increased incidence of snakebite during summer has been also observed in many other countries including Iran,18 India19 and Nepal.20 We found that of 37 cases of patients with severe injury severity, 68% occurred during summer. Furthermore, among the 10 fatalities we observed, 8 of those occurred during summer. While the severity of snakebite is determined by several factors, including the patient’s age, body volume, underlying conditions and the type and amount of toxin,7 the seasonal variation in venom composition and toxicity has also been reported.21 For certain species of snakes, such as the European viper (Vipera aspis), it was reported that the toxic severity of their venom differs by season with bites received in spring or summer being more severe than in autumn/winter.22 In our study, the population at risk was predominantly composed of adult males living in rural areas who were bitten either while working or engaging in leisure activities. More male victims are likely because of their occupations such as farming and other outdoor activities (i.e. sports or leisure activity). Similar demographic characteristics such as gender and the occupation of snakebite patients were reported in other countries.23,24 Agricultural and pastoral activities were recognised as particularly high risk factors for snakebite.25 While the majority of snakebites occur in those aged 10–40 y in many other areas of the world,26 in our study >70% of snakebite victims were aged 40–79 y. In South Korea, middle-aged and older groups are the most productive members of rural communities and are also the main age groups involved in agriculture, forestry and fishery. Adults in the middle-aged and older groups are the primary population involved daily in outdoor occupations and leisure activities in South Korea. Based on the EMR-ISS, >88% of the snakebites were classified as mild injuries. The EMR-ISS is based on the NISS, which was originally developed to assess the severity of injuries in trauma patients, particularly those with multiple injuries, therefore using the EMR-ISS does not indicate the severity of the envenomation in snakebite patients. Previous studies of snakebite have used snakebite severity scales to categorise snakebite severity and correctly classify envenomated patients.7,27 However, due to the limited clinical information available, we were unable to calculate snakebite severity. Therefore, careful interpretation is necessary regarding the EMR-ISS in respect to snakebite severity. The overall case fatality rate observed in the current study was 0.7%, which was comparable with the case fatality rate in India (1.0%)28 but higher than that of the USA (0.1%) and lower than Morocco (3.9%), Bolivia (4.4%) and Uruguay (2.5%).29 The low case fatality rate may be because all of the patients in this study were ED-visiting patients at the tertiary hospitals in South Korea. These patients may have received timely and excellent treatment from the EDs and therefore there was a lower case fatality rate. However, our case fatality rate was higher than some countries such as the USA (0.1%).30 Although we observed a low case fatality rate, of the total 1335 snakebite cases, 66.7% of them were clinically important injuries that required admission, transport to another hospital or resulted in death in the ED. This demonstrates the high morbidity and injury burden of snakebite in South Korea. Furthermore, one previous study reported that 13.8% of the venomous snakebite cases diagnosed and treated at an ED were associated with adverse cardiovascular events after a venomous snakebite in South Korea.6 There are several limitations in this study. First, we used the EDIIS registry, which has 23 participating hospitals. While the participating hospitals were sampled by the KCDC considering geographical location and the number of patients, these data do not represent the total number of snakebite cases in South Korea. While there are no national statistics on the incidence of snakebite in South Korea, a previous study estimated that the annual incidence of snakebite ranged from 192 to 621 with an average of five deaths each year.31 Another limitation is that information on the type of snake as well as details of the clinical symptoms and the treatment patients received is not available in the EDIIS. Therefore we do not know how many of the 1335 snakebite patients received antivenom. The severity of the envenomation is related to the species as well as to the size of the snake, which determines the composition and quantity of the venom injected.30 Venom from Gloydius contains several enzymes that induce local pain, erythema and swelling at the bite site.32 It was also reported that occasionally Gloydius venom can result in the development of ecchymosis and gastrointestinal bleeding by causing strong platelet aggregation.33Rhabdophis venom also has strong blood coagulation activity that can induce hemorrhagic symptoms including severe hypofibrinogenemia.34 However, it was reported that the venoms of the four species of venomous snakes residing in South Korea are not particularly toxic, thus systemic symptoms resulting from these snakes are rare.8 While all four venomous species are found throughout South Korea (Figure 3),35 previous studies have reported Gloydius ussuriensis to be the most common cause of snakebite in South Korea due to its large population and their easily accessible habitation areas such as mountains and farming areas.8 Figure 3. Open in new tabDownload slide Geographical distribution of four venomous species of snakes in South Korea (adapted from the National Institute of Biological Resources Red Data Book of Endangered Amphibians and Reptiles in Korea). Figure 3. Open in new tabDownload slide Geographical distribution of four venomous species of snakes in South Korea (adapted from the National Institute of Biological Resources Red Data Book of Endangered Amphibians and Reptiles in Korea). Insufficient epidemiological data on snakebite have hindered consideration of snakebite as an important public health problem in South Korea. This study provides essential information to understand and assess the burden and distribution of snakebite in South Korea to ensure appropriate prevention and control interventions in South Korea. Further studies using nationally representative data are needed to monitor the magnitude of the problem, its management and treatment. Authors’ contributions: All of the authors contributed substantially to this study: MZFS, SYK, SDS and KMS conceptualised this study. MZFS, SDS, SYK, JK and YSR developed the methodology. MZFS, SYK and JK analysed the data set. MZFS and SYK drafted the manuscript and all of the authors contributed to revision of the manuscript. All of the authors read and approved the final manuscript. Funding: The authors received no specific funding for this work. Competing interests: None declared. Ethical approval: This study was approved by the Institutional Review Board of Seoul National University Hospital (IRB No. 1809-028-969). Informed consent was waived by the board. References 1 Warrell DA . Snake bite . Lancet . 2010 ; 375 ( 9708 ): 77 – 88 . Google Scholar Crossref Search ADS PubMed WorldCat 2 Gold BS , Dart RC , Barish RA . Bites of venomous snakes . N Engl J Med . 2002 ; 347 ( 5 ): 347 – 56 . Google Scholar Crossref Search ADS PubMed WorldCat 3 World Health Organization . Prevalence of snakebite envenoming. http://www.who.int/snakebites/epidemiology/en/ (accessed 9 August 2018 ). 4 Habib AG , Brown NI . The snakebite problem and antivenom crisis from a health-economic perspective . Toxicon . 2018 ; 150 : 115 – 23 . Google Scholar Crossref Search ADS PubMed WorldCat 5 The Lancet . Snake-bite envenoming: a priority neglected tropical disease . Lancet . 2017 ; 390 ( 10089 ): 2 . WorldCat 6 Kim OH , Lee JW , Kim HI , et al. Adverse cardiovascular events after a venomous snakebite in Korea . Yonsei Med J . 2016 ; 57 ( 2 ): 512 – 7 . Google Scholar Crossref Search ADS PubMed WorldCat 7 Kang S , Moon J , Chun B . Does the traditional snakebite severity score correctly classify envenomated patients? Clin Exp Emerg Med . 2016 ; 3 ( 1 ): 34 – 40 . Google Scholar Crossref Search ADS PubMed WorldCat 8 Rha JH , Kwon SM , Oh JR , et al. Snakebite in Korea: a guideline to primary surgical management . Yonsei Med J . 2015 ; 56 ( 5 ): 1443 – 8 . Google Scholar Crossref Search ADS PubMed WorldCat 9 Ariaratnam CA , Sheriff MH , Theakston RD , et al. Distinctive epidemiologic and clinical features of common krait (bungarus caeruleus) bites in Sri Lanka . Am J Trop Med Hyg . 2008 ; 79 ( 3 ): 458 – 62 . Google Scholar Crossref Search ADS PubMed WorldCat 10 Mohapatra B , Warrell DA , Suraweera W , et al. Snakebite mortality in India: a nationally representative mortality survey . PLoS Negl Trop Dis . 2011 ; 5 ( 4 ): e1018 . Google Scholar Crossref Search ADS PubMed WorldCat 11 Kim JS , Yang JW , Kim MS , et al. Coagulopathy in patients who experience snakebite . Korean J Intern Med . 2008 ; 23 ( 2 ): 94 – 9 . Google Scholar Crossref Search ADS PubMed WorldCat 12 Park GJ , Ro YS , Shin SD , et al. Preventive effects of car safety seat use on clinical outcomes in infants and young children with road traffic injuries: A 7-year observational study . Injury . 2018 ; 49 ( 6 ): 1097 – 103 . Google Scholar Crossref Search ADS PubMed WorldCat 13 National emergency medical center . http://www.e-gen.or.kr/nemc/emergency_medical_services_system.do?viewPage=structural_elements (accessed 9 August 2018). 14 Kim J , Shin SD , Im TH , et al. Development and validation of the excess mortality ratio-adjusted injury severity score using the International Classification of Diseases 10th edition . Acad Emerg Med . 2009 ; 16 ( 5 ): 454 – 64 . Google Scholar Crossref Search ADS PubMed WorldCat 15 Suleman MM , Shahab S , Rab MA . Snake bite in the Thar Desert . J Pak Med Assoc . 1998 ; 48 ( 10 ): 306 – 8 . Google Scholar PubMed WorldCat 16 Chaudhari TS , Patil TB , Paithankar MM , et al. Predictors of mortality in patients of poisonous snake bite: experience from a tertiary care hospital in central India . Int J Crit Illn Inj Sci . 2014 ; 4 ( 2 ): 101 – 7 . Google Scholar Crossref Search ADS PubMed WorldCat 17 Southwood A , Avens L . Physiological, behavioral, and ecological aspects of migration in reptiles . J Comp Physiol B . 2010 ; 180 ( 1 ): 1 – 23 . Google Scholar Crossref Search ADS PubMed WorldCat 18 Dehghani R , Rabani D , Panjeh Shahi M , et al. Incidence of snake bites in Kashan, Iran during an eight year period (2004–2011) . Arch Trauma Res . 2012 ; 1 ( 2 ): 67 – 71 . Google Scholar Crossref Search ADS PubMed WorldCat 19 Kirte RC , Wahab SN , Bhathkule PR . Record based study of snake bite cases admitted at Shri Vasantrao Naik Government Medical College & Hospital, Yavatmal (Maharashtra) . Indian J Public Health . 2006 ; 50 ( 1 ): 35 – 7 . Google Scholar PubMed WorldCat 20 Pandey DP . Epidemiology of snakebites based on field survey in Chitwan and Nawalparasi districts, Nepal . J Med Toxicol . 2007 ; 3 ( 4 ): 164 – 8 . Google Scholar Crossref Search ADS PubMed WorldCat 21 Nelson LLN , Howland MA , Hoffman R , et al. Goldfrank’s toxicologic emergencies . San Francisco, CA : McGraw Hill ; 2011 . Google Preview WorldCat COPAC 22 Chippaux JP , Williams V , White J . Snake venom variability: methods of study, results and interpretation . Toxicon . 1991 ; 29 ( 11 ): 1279 – 303 . Google Scholar Crossref Search ADS PubMed WorldCat 23 El Hattimy F , Chafiq F , Hami H , et al. Geographical distribution of health indicators related to snake bites and envenomation in Morocco between 1999 and 2013 . Epidemiol Health . 2018 ; 40 : e2018024 . Google Scholar Crossref Search ADS PubMed WorldCat 24 Dehghani R , Fathi B , Shahi MP , et al. Ten years of snakebites in Iran . Toxicon . 2014 ; 90 : 291 – 8 . Google Scholar Crossref Search ADS PubMed WorldCat 25 Chippaux JP , Postigo JR . Appraisal of snakebite incidence and mortality in Bolivia . Toxicon . 2014 ; 84 : 28 – 35 . Google Scholar Crossref Search ADS PubMed WorldCat 26 Gutierrez JM , Calvete JJ , Habib AG , et al. Snakebite envenoming . Nat Rev Dis Primers . 2017 ; 3 : 17063 . Google Scholar Crossref Search ADS PubMed WorldCat 27 Tirosh-Levy S , Solomovich R , Comte J , et al. Daboia (vipera) Palaestinae envenomation in horses: clinical and hematological signs, risk factors for mortality and construction of a novel severity scoring system . Toxicon . 2017 ; 137 : 58 – 64 . Google Scholar Crossref Search ADS PubMed WorldCat 28 Sarkhel S , Ghosh R , Mana K , et al. A hospital based epidemiological study of snakebite in Paschim Medinipur district, West Bengal, India . Toxicol Rep . 2017 ; 4 : 415 – 9 . Google Scholar Crossref Search ADS PubMed WorldCat 29 Chafiq F , El Hattimy F , Rhalem N , et al. Snakebites notified to the poison control center of Morocco between 2009 and 2013 . J Venom Anim Toxins Incl Trop Dis . 2016 ; 22 : 8 . Google Scholar Crossref Search ADS PubMed WorldCat 30 Chippaux JP . Incidence and mortality due to snakebite in the Americas . PLoS Negl Trop Dis . 2017 ; 11 ( 6 ): e0005662 . Google Scholar Crossref Search ADS PubMed WorldCat 31 Lim H , Kang H , Kim K . Antivenom for snake bite in Korea . J Korean Med Assoc . 2013 ; 56 ( 12 ): 1091 – 103 . Google Scholar Crossref Search ADS WorldCat 32 Chiba T , Koga H , Kimura N , et al. Clinical condition and management of 114 mamushi (gloydius blomhoffii) bites in a general hospital in Japan . Intern Med . 2018 ; 57 ( 8 ): 1075 – 80 . Google Scholar Crossref Search ADS PubMed WorldCat 33 Hifumi T , Sakai A , Kondo Y , et al. Venomous snake bites: clinical diagnosis and treatment . J Intensive Care . 2015 ; 3 ( 1 ): 16 . Google Scholar Crossref Search ADS PubMed WorldCat 34 Hifumi T , Murakawa M , Sakai A , et al. Potentially fatal coagulopathy secondary to yamakagashi (rhabdophis tigrinus) bites that completely recovered with antivenom treatment . Acute Med Surg . 2015 ; 2 ( 2 ): 123 – 6 . Google Scholar Crossref Search ADS PubMed WorldCat 35 National Red List . Red Data Book of Endangered Amphibians and Reptiles in Korea . Incheon, South Korea : National Institute of Biological Resources ; 2011 . Google Preview WorldCat COPAC © The Author(s) 2019. Published by Oxford University Press on behalf of Royal Society of Tropical Medicine and Hygiene. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)
TI - Epidemiological profile and outcomes of snakebite injuries treated in emergency departments in South Korea, 2011–2016: a descriptive study
JO - Transactions of The Royal Society of Tropical Medicine and Hygiene
DO - 10.1093/trstmh/trz050
DA - 2019-10-11
UR - https://www.deepdyve.com/lp/oxford-university-press/epidemiological-profile-and-outcomes-of-snakebite-injuries-treated-in-m0uNmMEDVV
SP - 590
VL - 113
IS - 10
DP - DeepDyve
ER -