|SHORT RESEARCH COMMUNICATION
|Year : 2019 | Volume
| Issue : 3 | Page : 268-271
A comparative study of the trends in epidemiological aspects of Lyme disease infections in Korea and Japan, 2011–2016
Won chang Lee1, Myeong jin Lee2, Kwang hoon Choi1, Han sung Chung1, Nong hoon Choe1
1 College of Veterinary Medicine, Konkuk University, Seoul, Korea
2 Faculty of Health and Nutrition, Otemae University, Osaka, Japan
|Date of Submission||23-Mar-2018|
|Date of Acceptance||01-Mar-2019|
|Date of Web Publication||09-Jul-2020|
Prof. Nong hoon Choe
College of Veterinary Medicine, Konkuk University, Seoul–05029
Source of Support: None, Conflict of Interest: None
Lyme disease (LD) is one of the most prevalent tick-borne emerging infections in North America, Europe, and far Eastern Asia including Korea and Japan. This study was undertaken with the aim of a comparative and quantitative analysis of the epidemiological aspects of LD infections in Korea and Japan from 2011 to 2016. The raw data analyzed in this study were obtained from the websites of the Korea Center for Disease Control and Prevention (KCDC), Korea, and the National Institute of Infectious Diseases (NIID), Japan. In total 65 cases of LD were observed with a cumulative incidence rate (CIR) of 0.22 per million population in Korea from 2011 to 2016. During the same period in Japan, there were 75 cases of LD with a CIR of 0.10 [significantly higher than that in Korea (p <0.01)]. Further, the results showed that in Korea, LD incidence was slightly higher in women than in men; but in Japan, the case was reverse, with incidence much higher in men than women. The proportion of cases differed significantly by age-specific adjusted groups within both countries (p <0.01). In both the countries, the incidence of LD was highest among those aged ≤20 yr (93.8% cases in Korea, and 94.7% cases in Japan). Cases peaked in autumn (46.7% of total cases) in Korea and in summer (60.0%) in Japan (p <0.01). The counties in rural areas had a significantly higher proportion of cases than the capital cities in both the countries (p <0.01). The study indicates that LD in Korea and Japan is an emerging zoonosis, and pose a serious risk to public health. The results underscore the continued emergency of LD and provide a basis for targeting prevention campaigns to a population with increasing incidence. Proper information, education and communication (IEC) activities can be helpful in reducing the spread of infection.
Keywords: Epidemic aspects; Japan; Korea; Lyme disease; risk factors
|How to cite this article:|
Lee Wc, Lee Mj, Choi Kh, Chung Hs, Choe Nh. A comparative study of the trends in epidemiological aspects of Lyme disease infections in Korea and Japan, 2011–2016. J Vector Borne Dis 2019;56:268-71
|How to cite this URL:|
Lee Wc, Lee Mj, Choi Kh, Chung Hs, Choe Nh. A comparative study of the trends in epidemiological aspects of Lyme disease infections in Korea and Japan, 2011–2016. J Vector Borne Dis [serial online] 2019 [cited 2020 Aug 5];56:268-71. Available from: http://www.jvbd.org/text.asp?2019/56/3/268/289396
Lyme disease (LD) or Lyme borreliosis is the most prevalent tick-borne zoonosis and important emerging infection in North America, Europe, and Far Eastern Asia including Korea and Japan,,,. The etiological agents include at least three spirochete species: Borrelia burgdorferi, B. garinii and B. afzelii. Human Lyme borreliosis is vectored by Ixodes ticks, specifically, Ixodes scapularis, I. ricinus, I. pacificus, and I. persulcatus,,,,. Ixodes persulcatus is present in Russia and Far East Asia and has been implicated as a vector of several human pathogens including Lyme disease,. The majority of patients with LD develop a characteristic rash and erythema migrans, accompanied by symptoms of fever, malaise, fatigue, headache, myalgia, or arthralgia,. The LD was first described in 1977, following investigation of a cluster of arthritis cases among children living near Lyme, Connecticut in the United States,. In Korea, the first case was reported by the Korea Center for Disease Control and Prevention (KCDC) on June 31, 2012, and in Japan was first reported in 1986 according to the National Institute of Infectious Disease (NIID). Lyme disease occurs naturally in reservoir hosts, like mice, squirrels, shrews, and other vertebrates, including birds,,. Borrelia burgdorferi, the causative agent of LD, is of considerable concern to all of us and the veterinary profession is deeply involved with the public health service in studying its implications,. In the light of this situation, in Korea, the Infectious Disease Control and Prevention Act has classified human LD among group IV notifiable infectious diseases9. Likewise, Japan’s Infectious Disease Control Law has also classified human LD as a category IV notifiable infectious disease.
The present study is significant because it may be the first to comparably describe the epidemiological aspects of LD between Korea and Japan during the period 2011 to 2016. This study assessed the pattern of LD in terms of epidemiological aspects and risk factors in Korea and Japan from 2011 to 2016 under six headings: cumulative incidence rate (CIR), epidemic aspects including cases related to gender, male-to-female morbidity ratio (MFMR), age and related risk factors such as the seasonality and habitat (capital city and the other counties) among the LD infection cases.
The raw data on confirmed LD cases in Korea (n = 65) were obtained from the National Notified Disease Surveillance System (web site) of KCDC—an agency of the Ministry of Health and Welfare. The data on reported LD cases in Japan (n = 75) were obtained from the National Epidemiological Surveillance of Infectious Diseases Surveillance System (web site), administered by the NIID in Japan.
In the study, the CIR of LD cases per million population was estimated by the criteria established and calculated by the World Health Organization (WHO). Statistically significant differences between the epidemiological aspects and risk factors were determined using Pearson’s chi-square test or paired t-test. All the data analyses were performed in Microsoft Excel 2010 (Microsoft Co. Redmond, WA, USA). Results were considered statistically significant at p-value <0.05.
[Table 1] shows the comparative and quantitative analyses of surveillance for the epidemiological aspects of LD and their emerging relevance in Korea and Japan. We observed 65 LD cases with a CIR of 0.22 per million population in Korea from 2011 to 2016. During the same period in Japan, there were 75 cases of LD with a CIR of 0.10. When compared, the CIR of LD in Korea was much higher than that of in Japan (p <0.01). This difference level could be attributed to the divergence in the influence of host/vectors, climate, and geographical and cultural characteristics between the two countries; though geographically Korea and Japan are very close to each other, and they share similarities in several aspects such as climate, lifestyle, and sociocultural system,,.
|Table 1: Comparative observation of epidemiological aspects of Lyme disease between Korea and Japan, 2011–2016|
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The results also showed that in Japan, significantly more men were infected (MFMR = 2.13) compared to women (p <0.01); however, in Korea, there was no significant difference between gender. These remarkable differences in gender distribution are believed to reflect cultural differences between Korea and Japan in terms of lifestyle in the activities, clothes, and ornamentations. A similar study in the United States from 1992 to 2006 reported 53.1% LD infection occurrence among males yielding an average annual incidence rate of 6.3 cases per 100,000 population in comparison to 5.4 cases for females. The incidence rates increased disproportionately among males compared with females.
Classification of the LD cases in Korea by age-adjusted groups indicated that 5.3% of the cases belonged to the group aged ≤19 yr, 30.8% were aged between 20-39 yr, 46.1% were aged between 40–59 and 16.9% were aged ≥60 yr (p <0.01). In Japan, the proportions for the same age groups were 5.3, 22.7, 36.0 and 36.0%, respectively (p <0.01) [Figure 1]. The distributions by age–adjusted groups were similar in Korea and Japan, and over 93.8~94.7% of the total cases occurred in over 20-yr-old age bracket, clearly showing a higher incidence in the elderly. The higher incidence in the elderly may be due to an increased risk of infection owing to increased outdoor activities and fieldwork in an endemic area of LD,,. However, this varies from the study reported from U.S., wherein the reported age ranged from <1 to 101 yr and were bimodal in distribution; and the average annual incidence rates peaked among children aged 5–9 yr (8.6 per 100,000) and adults aged 55–59 yr (7.8 per 100,000). The lowest rate was reported among adults aged 20–24 yr (3.0 per 100,000).
|Figure 1: Distribution rates of Lyme disease infection by age-adjusted groups in Korea and Japan, 2011–2016.|
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Analyses of the seasonal pattern of reported LD cases in Korea showed that 7.7% of the cases occurred in the spring, 35.4% in the summer, 46.1% in the autumn, and 10.8% in the winter demonstrating significant seasonal variation in the distribution of the cases (p <0.01). In Japan, the proportions for these seasons were 9.3, 60.0, 26.7 and 4.0%, respectively [Figure 2], again representing significant seasonal variation (p <0.01). During the period, reported cases in Korea increased markedly in June, peaked in November, and began decreasing during the end of November with the cooling of seasonal temperatures. Meanwhile, in Japan, reported cases increased from early summer until the middle of autumn, which might be the result of a flooding event during the period, [Figure 2]. This is remarkable, as in a surveillance study in the United States, though the cases occurred in all the months of the year; the majority (25.8% of 48,413 cases) of patients had onset during June, July (30.0%), and August (12.1%), the three months in which ticks most actively seek mammalian hosts and human outdoor activity is also highest.
|Figure 2: Monthly distribution pattern in the incidence rates of Lyme disease infections in Korea and Japan, 2011–2016|
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The study also compared the incidence of LD between capital cities and each county, both of which are intensely urbanized, as well as other regions including counties in rural communities. In Korea, 24 cases (36.9% of total cases) were reported in the capital city of Seoul, home to approximately 20% of the Korean population, between 2011 and 2016. In comparison 41 cases (63.1% of total cases), were reported in other regions of the county, demonstrating a significantly higher incidence than the capital city (p <0.05). Similarly, in Japan, 14 cases (18.7% of total cases) were reported in the capital city of Tokyo, accounting for 11% of the national population, while 61 cases (81.3% of total cases) were reported in other regions, suggesting the lack of a significant regional variation (p <0.01).
The number of reported cases of LD continues to increase in Korea and Japan, underscoring the need for targeted prevention strategies, early disease recognition and treatment, and a sustainable surveillance system. During the 5-yr study period, incidence increased disproportionately among elderly persons. Moreover, despite the limitations of national surveillance data, these epidemic findings are useful in defining demographics, distribution, and trends in LD cases.
In conclusion, we observed that there is a similar pattern of epidemiological aspects of LD cases in Korea and Japan. These results underscore the continued emergency of LD and provide a basis for targeting prevention campaigns to a population with increasing incidence. For example, to prevent possible LD transmission from ticks, the use of insect repellent needs to be continued. Proper clothing like tucking pants into boots, shirt into pants, and keeping sleeves rolled down may further prevent transmission,,,,,,. This information might act as an useful reference for further studies of LD in Korea and Japan.
Ethical statement: Not applicable.
Conflict of interest: No potential conflict of interest exists.
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[Figure 1], [Figure 2]