This study was performed to find out the clusters with high parasite infection risk to discuss the geographical pattern. Clusters were detected using SatScan software, which is a statistical spatial scan program using Kulldorff’s scan statistic. Information on the parasitic infection cases in Korea 2011–2019 were collected from the Korea Centers for Disease Control and Prevention. Clusters of
Parasitic infection rate in Republic of Korea has decreased ever since the national public health project (the Parasite Disease Prevention Act) took effect in 1966. According to National Survey on Parasitic Infection, which has been conducted every 5–7 years, the overall helminth egg positive rate was 2.6% in the 8th survey, decreased from 2.7% of the 7th survey, yet the estimated number of infections nationwide was about 1.3 million [
This study was performed under the regulation of the IRB Committee of The Catholic University of Korea (No. MIRB-20200529-002). This research adhered to the tenets of the Declaration of Helsinki.
The nationwide parasitic infection cases reported for 9 years (2011–2019) were collected from 16 administrative districts by the Korea Disease Control and Prevention Agency (KCDA) [
The population data of 16 administrative divisions 2011–2019 were obtained from the Korean Statistical Information Service [
SaTScan Software using the spatial scan statistic [
With 5% maximum cluster size, Ulsan, Daegu, Jeju-do, and Gangwon-do were clustered. Ulsan was the most likely cluster (LLR) with relative risk (RR) of 6.2, indicating that total parasite infection risk in Ulsan was 6.2 times higher than in the other districts. Followed were Daegu, Jeju-do and Gangwon-do in order of their likelihood ratio. With 15% maximum window size, Busan and Gyeongsangnam-do was the most likely cluster, indicating parasitic infection risk in Busan and Gyeongsangnam-do area was 8.7 times higher than other areas. With 25% maximum window size, Busan, Gyeongsangnam-do, Ulsan and Daegu were the most likely cluster, indicating the total parasite infection risk in these districts was 15 times higher than in the other districts (
With 5% maximum cluster size, the cases of
For intestinal trematodes, with 5% maximum cluster size, the most likely cluster was Ulsan with relative risk of 2.2, indicating that the intestinal trematode infections in Ulsan was 2.2 times higher than in the other areas. With 15% maximum cluster size, the most likely cluster was Busan and Gyeongsangnam-do with relative risk of 28.4. With 25% maximum cluster size, the most likely cluster was Busan, Gyeongsangnam-do and Ulsan with relative risk of 33.7. In summary, the intestinal trematode infection was of high risk in Gyeongsangnam-do region.
The clusters of
With 5% maximum cluster size, Gangwon-do was the most likely cluster with relative risk of 16, indicating
This study has provided the clusters with high risk of parasitic infection in Korea from 2011 to 2019, by using spatial scan analysis. Depending on the transmission of infections, the infections are respectively divided into soil-borne, fish-borne, and contact-borne.
The authors declare no conflict of interest related to this study.
Clusters detected in general parasitic infections by window size. Numbers identifying the administrative districts are referred to
Clusters detected from
The cumulated parasite infection cases and population for 2011–2019 by administrative district
District (no.) | Population | No. of infection cases of | |||||
---|---|---|---|---|---|---|---|
Intestinal trematodes | |||||||
Seoul (1) | 89,996,828 | 17 | 158 | 421 | 59 | 6 | 185 |
Busan (2) | 31,474,736 | 3 | 514 | 5,265 | 898 | 0 | 11 |
Daegu (3) | 22,355,184 | 1 | 114 | 1,849 | 178 | 1 | 226 |
Incheon (4) | 26,156,739 | 6 | 41 | 87 | 5 | 0 | 10 |
Gwangju (5) | 13,202,461 | 1 | 17 | 479 | 33 | 1 | 121 |
Daejeon (6) | 13,604,984 | 9 | 92 | 227 | 27 | 0 | 134 |
Ulsan (7) | 10,420,219 | 0 | 93 | 2,739 | 169 | 0 | 63 |
Gyeonggi-do (8) | 113,053,274 | 4 | 152 | 279 | 60 | 2 | 192 |
Gangwon-do (9) | 13,896,792 | 1 | 5 | 16 | 2 | 0 | 788 |
Chungcheongbuk-do (10) | 14,249,464 | 0 | 6 | 217 | 28 | 0 | 10 |
Chungcheongnam-do (11) | 18,781,102 | 0 | 0 | 0 | 0 | 0 | 8 |
Jeollabuk-do (12) | 16,736,755 | 15 | 32 | 188 | 44 | 7 | 47 |
Jeollanam-do (13) | 17,097,958 | 0 | 0 | 20 | 0 | 0 | 2 |
Gyeongsangbuk-do (14) | 24,235,379 | 0 | 0 | 146 | 52 | 0 | 0 |
Gyeongsangnam-do (15) | 30,167,674 | 4 | 538 | 4,728 | 1,988 | 1 | 24 |
Jeju-do (16) | 5,622,276 | 0 | 0 | 3 | 1 | 0 | 551 |
Total | 461,051,825 | 61 | 1,762 | 16,664 | 3,544 | 18 | 2,372 |
Clusters detected from general parasite infection by window size
Window Size | District | Case No. | Relative risk | Log likelihood ratio | |
---|---|---|---|---|---|
5% | Ulsan | 3,064 | 6.2 | 2,876.845 | <0.001 |
Daegu | 2,369 | 2.11 | 488.693 | <0.001 | |
Jeju-do | 555 | 1.88 | 89.688 | <0.001 | |
Gangwon-do | 812 | 1.11 | 3.908 | 0.024 | |
| |||||
15% | Busan, Gyeongsangnam-do | 13,974 | 8.67 | 12,945.557 | <0.001 |
Jeju-do | 555 | 1.88 | 89.688 | <0.001 | |
| |||||
25% | Busan, Gyeongsangnam-do, Ulsan, Daegu | 19,407 | 15.03 | 19,526.059 | <0.001 |
Clusters detected from
Window size | District | Case No. | Relative risk | Log likelihood ratio | |
---|---|---|---|---|---|
5% | Jeollabuk-do | 15 | 8.66 | 17.414 | <0.001 |
Daejeon | 9 | 5.69 | 7.742 | <0.001 | |
15% | Jeollabuk-do, Daejeon | 24 | 9.21 | 26.936 | <0.001 |
25% | Jeollabuk-do, Daejeon | 24 | 9.21 | 26.936 | <0.001 |
| |||||
5% | Ulsan | 93 | 2.41 | 26.531 | <0.001 |
Daejeon | 92 | 1.81 | 12.966 | <0.001 | |
Daegu | 114 | 1.36 | 4.562 | 0.011 | |
15% | Busan, Gyeongsangnam-do | 1,052 | 9.6 | 1,030.771 | <0.001 |
Daejeon | 92 | 1.81 | 12.966 | <0.001 | |
25% | Busan, Gyeongsangnam-do, Ulsan | 1,145 | 10.02 | 1,088.969 | <0.001 |
Daejeon | 92 | 1.81 | 12.966 | <0.001 |
Clusters detected from
Window size | District | Case No. | Relative risk | Log likelihood ratio | |
---|---|---|---|---|---|
5% | Ulsan | 2,739 | 8.51 | 3252.351 | <0.001 |
Daegu | 1,849 | 2.45 | 524.628 | <0.001 | |
15% | Busan, Gyeongsangnam-do | 9,993 | 9.71 | 9847.711 | <0.001 |
Gyeongsangbuk-do, Daegu | 1,995 | 1.21 | 30.359 | <0.001 | |
25% | Busan, Gyeongsangnam-do, Ulsan, Daegu | 14,581 | 27.18 | 17321.082 | <0.001 |
| |||||
Intestinal trematodes | |||||
5% | Ulsan | 169 | 2.17 | 38.432 | <0.001 |
15% | Busan, Gyeongsangnam-do | 2,886 | 28.42 | 4200.849 | <0.001 |
25% | Busan, Gyeongsangnam-do, Ulsan | 3,055 | 33.72 | 4330.98 | <0.001 |
| |||||
5% | Jeollabuk-do | 7 | 16.89 | 11.5896 | <0.001 |
15% | Jeollabuk-do | 7 | 16.89 | 11.5896 | <0.001 |
25% | Jeollabuk-do | 7 | 16.89 | 11.5896 | <0.001 |
Clusters detected from
Window size | District | Case No. | Relative risk | Log likelihood ratio | |
---|---|---|---|---|---|
5% | Gangwon-do | 788 | 16.01 | 1,299.982 | <0.001 |
Jeju-do | 551 | 24.51 | 1,164.773 | <0.001 | |
Daegu | 226 | 2.07 | 44.449 | <0.001 | |
Daejeon | 134 | 1.97 | 23.916 | <0.001 | |
Gwangju | 121 | 1.82 | 17.406 | <0.001 | |
| |||||
15% | Gangwon-do | 788 | 16.01 | 1,299.982 | <0.001 |
Jeju-do | 551 | 24.51 | 1,164.773 | <0.001 | |
Daegu | 226 | 2.07 | 44.449 | <0.001 | |
Daejeon | 134 | 1.97 | 23.916 | <0.001 | |
Gwangju | 121 | 1.82 | 17.406 | <0.001 | |
| |||||
25% | Gangwon-do | 788 | 16.01 | 1,299.982 | <0.001 |
Jeju-do | 551 | 24.51 | 1,164.773 | <0.001 | |
Daegu | 226 | 2.07 | 44.449 | <0.001 | |
Daejeon | 134 | 1.97 | 23.916 | <0.001 | |
Gwangju | 121 | 1.82 | 17.406 | <0.001 |