
==== Front
New Microbes New Infect
New Microbes New Infect
New Microbes and New Infections
2052-2975
Elsevier

S2052-2975(24)00246-4
10.1016/j.nmni.2024.101462
101462
Letter to the Editor
Climate change and expansion of vector-borne diseases in Japan: A public health challenge
Wagatsuma Keita waga@med.niigata-u.ac.jp
⁎
Division of International Health (Public Health), Graduate School of Medical and Dental Sciences, Niigata University, Niigata, Japan
Institute for Research Administration, Niigata University, Niigata, Japan
⁎ Division of International Health (Public Health) Graduate School of Medical and Dental Sciences, Niigata University 1-757 Asahimachi dori, Chuo-ku, Niigata City, Niigata 951-8510, Japan. waga@med.niigata-u.ac.jp
22 8 2024
12 2024
22 8 2024
62 10146214 6 2024
19 8 2024
© 2024 The Author
2024
https://creativecommons.org/licenses/by-nc-nd/4.0/ This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
Keywords

Climate change
Vector-borne diseases
Severe fever with thrombocytopenia syndrome
Expansion
Japan
Handling Editor: Patricia Schlagenhauf
==== Body
pmcDear Editor:

I read with great interest the discussion by Pawan Kumar et al. on climate change and the emergence of the tick-borne Yezo virus (YEZV) originating from Hokkaido, Japan [1]. I strongly agree that the presence of YEZV in Asia, including Japan and mainland China, is alarming and underscores the need for active public health surveillance and the implementation of appropriate measures. Although only a small number of cases (i.e., seven cases from Japan and one case from mainland China) have been reported since 2014, regional systematic and routine risk assessments are necessary due to the lack of specific antiviral drugs. However, the impact of climate change on other tick-borne diseases in Japan has not been systematically clarified. Here, I aimed to discuss the changes in the epidemiological situations of vector-borne diseases in this region.

Fig. 1 illustrates the epidemiological curve and geographic spread of severe fever with thrombocytopenia syndrome (SFTS), a prevalent tick-borne disease in Japan. The initial case was identified in western Japan in January 2013. The patient, a healthy woman aged 50–59 years, was admitted to the hospital with high fever, malaise, vomiting, and hemorrhage, and was pronounced dead three days post-admission. Recently, there has been an annual increase in the number of SFTS cases, exceeding 120 in 2023 (Fig. 1A). Initially confined to the southern regions, the cases has recently been observed spreading eastward (Fig. 1B). Indeed, the prevention of this outbreak is a significant public health concern, as observational studies in Japan have shown that the fatality rate of SFTS is as high as 31.0 % [2].Fig. 1 Descriptive characteristics of severe fever with thrombocytopenia syndrome outbreaks in Japan in 2013–2023. (A) Long-term variations in numbers of cases by year. (B) Geographic distribution of cases. Epidemilogical data were extracted from the National Institute of Infectious Diseases, Japan (https://www.niid.go.jp/niid/en/).

Fig. 1

To the best of my knowledge, there is limited evidence suggesting that recent human-induced climate change may contribute to the expansion of vector-borne diseases in unique island regions such as Japan, which lies between temperate and tropical zones [3]. In general, ambinet temperature fluctuations due to climate change often create conditions favorable for the survival of vectors and viral viability. In Japan, non-endemic vector-borne diseases like dengue fever have been observed in Tokyo since 2014, likely due to meteorological changes that favor the survival of vector mosquitoes [3]. The dengue vector mosquito Aedes albopictus can survive at an annual average temperature of 11.0 °C and is expanding its distribution northwards [3]. In the 1950s, its distribution was limited to Tochigi Prefecture, but by the 2000s, it had spread to the northern Tohoku region [3]. Indeed, a study by Hayashi et al. projected that dengue fever transmission could be observed throughout Japan by 2100 under an representative concentration pathway (RCP) 8.5 scenario [4]. Additionally, ticks, which vector diseases like Japanese spotted fever, are increasing nationwide. Although the number of tsutsugamushi disease (scrub typhus) cases has declined recently, the number of cases remains high [3]. The end of the epidemic season for Japanese spotted fever has shifted towards the end of the year in Japan, as rising temperatures have delayed the onset of winter, and a positive correlation between the number of cases of tsutsugamushi disease and the average temperature, precipitation, snowfall, and amount of accumulated snow has also been reported [3]. Furthermore, newly discovered tick-borne infections, such as Oz virus, have been reported in Japan recently [5].

In conclusion, the marked increase in vector-borne disease cases in Japan in recent years and the expansion of endemic areas to the north highlight the complex interplay of environmental and human factors. Establishing effective public health measures in Asia, including Japan, is crucial. These measures should include comprehensive public health policies, education on vector-borne diseases, and the development of future treatments. In particular, tailored policies that consider the specific characteristics of each community are essential for effectively controlling and mitigating the spread of these diseases. Given the imminent threat posed by global warming, countries worldwide, particularly in Asia, must diligently monitor for signs of vector-borne disease transmission through robust epidemiological surveillance. Nevertheless, future epidemiological studies characterising the causal relationship between climate change and transmission dynamics of vector-borne disease in Asia are critically needed.

Funding

None.

CRediT authorship contribution statement

Keita Wagatsuma: Conceptualization, Data curation, Formal analysis, Writing – original draft.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgments

None.
==== Refs
References

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