Epidemic Trends of Imported Shigellosis Cases in Korea and Japan, 2016–2020
1College of Veterinary Medicine, Konkuk University, Seoul, Korea, 2Faculty of Health and Nutrition, Otemae University, Osaka, Japan, 3Department of Otorhinolaryngology, Inha University Hospital, Incheon, 4Magok Sky Internal Medicine, Seoul, KoreaCorrespondence to:
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License, which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Korean J Aerosp Environ Med 2023; 33(3): 71-75
Published September 30, 2023
Copyright © Aerospace Medical Association of Korea.
Methods: We analyzed the raw data of imported Sg cases from the Korea Diseases Control and Prevention Agency and the National Institute of Infectious Diseases in Japan between 2016 and 2020.
Results: In Korea, there were a total of 596 Sg infections, including 353 cases from overseas travel-associated imported cases, with a cumulative incidence rate (CIR) of 0.23 per 100,000 populations. The CIR of imported Sg cases was 0.32 per 100,000 OTs. In Japan, during the same period, there were a total of 757 Sg cases, including 388 imported cases, with a CIR of 0.12 per 100,000 populations. The CIR of imported Sg cases was 0.50 per 100,000 OTs. The CIR of total Sg cases in Korea was higher than in Japan, but the CIR of imported cases in Korea was lower than in Japan (P<0.01). Additionally, the imported-to-domestic cases ratio of Sg in Korea (1.45) was higher than in Japan (1.05) (P<0.05).
Conclusion: Based on the trends in the epidemiological aspects of domestic and imported Sg infection cases in both countries, a robust information system is needed to provide effective warnings and preventive measures for travelers visiting high-risk areas.
Shigellosis (Sg), caused by Shigella bacteria, is a significant cause of bloody diarrhea and continues to pose a substantial burden, particularly in developing countries. Shigella belongs to the family Enterobacteriaceae and includes four species:
In both Korea and Japan, Sg outbreaks are significant food- and waterborne illnesses. They have been classified as notifiable infectious diseases in these countries. The Communicable Disease Prevention Act of the Korea Disease Control and Prevention Agency (KDCA) designates it as a category-II notifiable infectious disease, while the National Institute of Infectious Diseases (NIID) in Japan classifies it as a category-III notifiable infectious disease. Although the number of cases has significantly decreased since the 1960s to 1970s, numerous cases of Sg, including imported cases, are still reported annually in both countries [3-12]. The World Health Organization (WHO) estimates that Sg causes at least 80 million cases of bloody diarrhea and 7,000,000 deaths worldwide each year . In the United States in 2016, 52 state and regional public health laboratories reported 12,597 cases of culture-confirmed Shigella infection to the Laboratory-based Enteric Disease Surveillance system .
Korea and Japan share geographical proximity and similar sociocultural characteristics, including food and lifestyle. Additionally, both countries have similar operating systems for epidemiological studies of food- and waterborne illnesses, ranging from terminology to identification methods [3-12]. The aim of this study was to analyze the current trends of Sg outbreaks, including imported cases among overseas travelers (OTs), in Korea and Japan from 2016 to 2020. This research aims to provide a better understanding of the current status of Sg and establish effective control measures for public health services, facilitating more informed future strategies.
II. MATERIALS AND METHODS
For this study, we obtained raw data on Sg cases in Korea and Japan from 2016 to 2020. In Korea, there were a total of 596 infections reported during this period. Among these cases, 353 were classified as imported cases, indicating individuals who acquired the infection during travel overseas. The data for Korea was collected from the infectious diseases surveillance websites available on the KCDA website .
In Japan, there were a total of 757 Sg infections reported between 2016 and 2020. Among these cases, 388 were classified as imported cases, indicating individuals who acquired the infection during travel overseas. The data for Japan was collected from the infectious diseases surveillance websites available on the NIID in Japan .
To analyze the data, the cumulative incidence rate (CIR) of Sg cases per 100,000 populations was calculated for both Korea and Japan using the criteria provided by the WHO. Statistical analysis was conducted to determine any significant differences in the epidemic indices. The Pearson’s chi-square test or paired t-test was used for this purpose. All data analysis was performed using Microsoft Excel 2010 (Microsoft). Results were considered statistically significant if the
In this comparative observation study, the CIR of Sg outbreaks, including imported cases, was analyzed for Korea and Japan between 2016 and 2020 (Table 1). In Korea, there were a total of 596 Sg infections, including 353 cases from travel-associated imported cases. The CIR of total Sg cases in Korea was 0.23 per 100,000 populations, while the CIR of imported Sg cases was 0.32 per 100,000 OTs. In Japan, there were a total of 757 Sg cases, including 388 imported cases. The CIR of total Sg cases in Japan was 0.12 per 100,000 populations, and the CIR of imported Sg cases was 0.50 per 100,000 OTs. The CIR of total Sg cases was higher in Korea compared to Japan, while the CIR of imported Sg cases was lower in Korea compared to Japan (
Furthermore, the presumptive origin of imported Sg infection cases among OTs differed between Korea and Japan (Table 2). In Korea, the majority of imported Sg cases were from Asia (330 cases or 93.5% of total 353 imported cases), followed by Oceania, Africa, Middle East, and Central & South America/Caribbean. In Japan, the majority of imported Sg cases were also from Asia (255 cases or 65.7% of total 388 imported cases), followed by Oceania, Africa, Europe, Middle East, Central & South America/Caribbean, U.S.A., and cases where multiple countries were visited or the origin was unknown. The region with the highest number of imported Sg cases among OTs was Asia for both Korea and Japan (
Sg is a significant public health concern in many developing countries, causing acute invasive enteric infections with symptoms of bloody diarrhea and leading to substantial morbidity and mortality [1,2]. In this study, we examined the epidemiological aspects of domestic and imported Sg cases in Korea and Japan from 2016 to 2020.
The CIR of Sg cases in Korea was higher than that in Japan. However, when considering imported cases among OTs, the CIR of imported Sg cases in Korea was lower than that in Japan. The IDCR in Korea was higher than in Japan. These differences in CIRs and IDCRs can be attributed to variations in the patterns of Sg infection cases imported by OTs.
The data strongly suggest that the frequency of Asian regions as the origins of Sg infections among Korean OTs is much higher compared to Japanese travelers. This can be influenced by differences in travel preferences and destinations between the two countries. For example, there were more Sg cases among Korean travelers to countries such as the Philippines, Vietnam, and India in the South Asia region. In contrast, Japanese travelers had more cases from destinations such as Indonesia, Cambodia, and Africa. These variations may be due to differences in travel behaviors, as well as the local transmission and living environment conditions (including food and water sanitation) in the respective travel destinations [13,14].
It is important to consider the periods when people in both countries undertake travel and the prevalence of Sg infections in the travel destination areas. The differences observed in the patterns of infection could be related to these factors. For instance, the higher number of Sg cases among Korean travelers to South Asian countries may be influenced by the prevalence of Sg in those regions during the corresponding period [1,2,7-12].
These findings highlight the need for effective surveillance and control measures for Sg, especially among OTs. Public health efforts should focus on promoting awareness about the risk of Sg during travel, emphasizing preventive measures such as proper hygiene practices and safe food and water consumption. Additionally, collaboration between countries can help facilitate information sharing and coordinate control strategies to reduce the burden of Sg infections among travelers.
Further studies and continued surveillance are necessary to monitor the changing patterns of Sg and develop targeted interventions for effective control and prevention of this disease in both Korea and Japan.
In this study, we conducted a comparative analysis of imported Sg cases in Korea and Japan from 2016 to 2020. The results highlight the differences in the epidemiological aspects of Sg cases between the two countries, with higher CIR of Sg in Korea compared to Japan. However, when considering imported cases among OTs, the CIR of imported Sg cases in Korea was lower than that in Japan. These findings indicate the importance of understanding the patterns of Sg infections among travelers and the need for effective control measures.
Further research is necessary to gain a comprehensive understanding of the current status of Sg outbreaks and to establish appropriate control measures in both countries. Continued surveillance and analysis of Sg cases will contribute to public health planning and strategy development. It is essential to have a robust information system that can effectively warn travelers about the risk of Sg infections and provide preventive measures, particularly for individuals traveling to areas with a higher risk of Sg transmission.
Overall, this study provides valuable insights into the epidemiology of imported Sg cases in Korea and Japan, highlighting the need for ongoing monitoring and prevention efforts. The findings can serve as a reference for future studies and contribute to the improvement of public health services in managing Sg outbreaks.
CONFLICTS OF INTEREST
We would like to acknowledge the KDCA and the NIID in Japan for providing the raw data on domestic and imported Sg cases used in this study. Their contribution is greatly appreciated.
Conceptualization: all authors. Data curative: all authors. Analysis and interpretation: all authors. Writing the original draft: all authors. Critical revision of the article: all authors. Final approval of the article: all authors. Overall responsibility: all authors.
Comparative observation on the epidemic indices of shigellosis outbreaks between Korea and Japan, 2016–2020
CIR: cumulative incidence rate, IDCR: imported-to-domestic cases ratio.
a)CIR: cumulative incidence rate per 100,000 populations.
b)CIR of cumulative incidence rate per 100,000 overseas travelers.
c)IDCR: imported-to-domestic cases ratio=imported cases/domestic cases.
Statistically significant levels, set at *
Comparative observation of the presumptive origin of imported shigellosis cases among overseas travelers in Korea and Japan, 2016–2020
|Presumptive origin region/countries||No. of cases (%)|
|Asia||330 (93.5)**||255 (65.7)|
|India||34 (9.6)||48 (12.4)|
|Indonesia||7 (2.0)||62 (16.0)**|
|Philippines||183 (51.8)**||50 (12.9)|
|Cambodia||20 (5.6)||20 (5.1)|
|Myanmar||3 (0.8)||19 (4.9)**|
|Vietnam||46 (13.0)**||13 (3.3)|
|Other’s||37 (10.5)||43 (11.1)|
|Oceania||4 (1.1)||21 (5.4)**|
|Africa||12 (3.4)||36 (9.3)**|
|Middle East||2 (0.6)||8 (2.0)|
|Central & South America/Caribbean||5 (1.4)||17 (4.4)**|
|Visited multiple countries & unknown||-||46 (11.9)|
Statistically significant levels, set at **
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