Division of International Health (Public Health), Graduate School of Medical and Dental Sciences, Niigata University, Niigata, Japan.
College of Health and Medicine, School of Medicine, University of Tasmania, Hobart, Tasmania, Australia.
PLoS One. 2021 Mar 25;16(3):e0248932. doi: 10.1371/journal.pone.0248932. eCollection 2021.
Few studies have examined the effects of inbound overseas travelers and meteorological conditions on the shift in human respiratory syncytial virus (HRSV) season in Japan. This study aims to test whether the number of inbound overseas travelers and meteorological conditions are associated with the onset week of HRSV epidemic season. The estimation of onset week for 46 prefectures (except for Okinawa prefecture) in Japan for 4-year period (2014-2017) was obtained from previous papers based on the national surveillance data. We obtained data on the yearly number of inbound overseas travelers and meteorological (yearly mean temperature and relative humidity) conditions from Japan National Tourism Organization (JNTO) and Japan Meteorological Agency (JMA), respectively. Multi-level mixed-effects linear regression analysis showed that every 1 person (per 100,000 population) increase in number of overall inbound overseas travelers led to an earlier onset week of HRSV epidemic season in the year by 0.02 week (coefficient -0.02; P<0.01). Higher mean temperature and higher relative humidity were also found to contribute to an earlier onset week by 0.30 week (coefficient -0.30; P<0.05) and 0.18 week (coefficient -0.18; P<0.01), respectively. Additionally, models that included the number of travelers from individual countries (Taiwan, South Korea, and China) except Australia showed that both the number of travelers from each country and meteorological conditions contributed to an earlier onset week. Our analysis showed the earlier onset week of HRSV epidemic season in Japan is associated with increased number of inbound overseas travelers, higher mean temperature, and relative humidity. The impact of international travelers on seasonality of HRSV can be further extended to investigations on the changes of various respiratory infectious diseases especially after the coronavirus disease 2019 (COVID-19) pandemic.
很少有研究探讨入境海外旅行者和气象条件对日本呼吸道合胞病毒（HRSV）季节变化的影响。本研究旨在检验入境海外旅行者人数和气象条件是否与 HRSV 流行季节的起始周有关。根据之前基于全国监测数据的论文，我们获得了日本 46 个都道府县（冲绳县除外）4 年（2014-2017 年）的起始周估计值。我们分别从日本国家旅游局（JNTO）和日本气象厅（JMA）获得了关于每年入境海外旅行者人数和气象（年平均温度和相对湿度）条件的数据。多水平混合效应线性回归分析表明，入境海外旅行者总人数每增加 1 人（每 10 万人），当年 HRSV 流行季节的起始周就会提前 0.02 周（系数-0.02；P<0.01）。较高的平均温度和相对湿度也会使起始周提前 0.30 周（系数-0.30；P<0.05）和 0.18 周（系数-0.18；P<0.01）。此外，包含除澳大利亚以外的台湾、韩国和中国等个别国家旅行者人数的模型表明，每个国家的旅行者人数和气象条件都有助于提前开始流行季节。我们的分析表明，日本 HRSV 流行季节的起始周提前与入境海外旅行者人数增加、平均温度升高和相对湿度升高有关。国际旅行者对 HRSV 季节性的影响可以进一步扩展到对各种呼吸道传染病变化的研究，特别是在 2019 年冠状病毒病（COVID-19）大流行之后。
