Fukusumi Munehisa, Arashiro Takeshi, Arima Yuzo, Matsui Tamano, Shimada Tomoe, Kinoshita Hitomi, Arashiro Ashley, Takasaki Tomohiko, Sunagawa Tomimasa, Oishi Kazunori
Infectious Disease Surveillance Center, National Institute of Infectious Diseases, Tokyo, Japan.
Osaka University Graduate School of Medicine, Osaka, Japan.
PLoS Negl Trop Dis. 2016 Aug 19;10(8):e0004924. doi: 10.1371/journal.pntd.0004924. eCollection 2016 Aug.
Dengue is becoming an increasing threat to non-endemic countries. In Japan, the reported number of imported cases has been rising, and the first domestic dengue outbreak in nearly 70 years was confirmed in 2014, highlighting the need for greater situational awareness and better-informed risk assessment.
Using national disease surveillance data and publically available traveler statistics, we compared monthly and yearly trends in the destination country-specific dengue notification rate per 100,000 Japanese travelers with those of domestic dengue cases in the respective country visited during 2006-2014. Comparisons were made for countries accounting for the majority of importations; yearly comparisons were restricted to countries where respective national surveillance data were publicly available.
There were 1007 imported Japanese dengue cases (Bali, Indonesia (n = 202), the Philippines (n = 230), Thailand (n = 160), and India (n = 152)). Consistent with historic local dengue seasonality, monthly notification rate among travelers peaked in August in Thailand, September in the Philippines, and in Bali during April with a smaller peak in August. While the number of travelers to Bali was greatest in August, the notification rate was highest in April. Annually, trends in the notification rate among travelers to the Philippines and Thailand also closely reflected local notification trends.
Travelers to dengue-endemic countries appear to serve as reliable "sentinels", with the trends in estimated risk of dengue infection among Japanese travelers closely reflecting local dengue trends, both seasonally and annually. Sentinel traveler surveillance can contribute to evidence-based pretravel advice, and help inform risk assessments and decision-making for importation and potentially for subsequent secondary transmission. As our approach takes advantage of traveler data that are readily available as a proxy denominator, sentinel traveler surveillance can be a practical surveillance tool that other countries could consider for implementation.
登革热对非流行国家的威胁日益增加。在日本，输入性病例报告数量一直在上升，2014年确认了近70年来的首次国内登革热疫情，这凸显了提高态势感知和进行更明智风险评估的必要性。
利用国家疾病监测数据和公开的旅行者统计数据，我们将每10万名日本旅行者前往特定目的地国家的登革热通报率的月度和年度趋势与2006 - 2014年期间在各访问国家的国内登革热病例趋势进行了比较。对占输入病例多数的国家进行了比较；年度比较仅限于可公开获取国家监测数据的国家。
有1007例日本输入性登革热病例（印度尼西亚巴厘岛（n = 202）、菲律宾（n = 230）、泰国（n = 160）和印度（n = 152））。与当地历史登革热季节性一致，旅行者中的月度通报率在泰国8月、菲律宾9月以及巴厘岛4月达到峰值，8月有一个较小的峰值。虽然8月前往巴厘岛的旅行者数量最多，但通报率在4月最高。每年，前往菲律宾和泰国的旅行者通报率趋势也密切反映当地通报趋势。
前往登革热流行国家的旅行者似乎是可靠的“哨兵”，日本旅行者中登革热感染估计风险的趋势在季节性和年度上都密切反映当地登革热趋势。哨兵旅行者监测可为基于证据的旅行前建议做出贡献，并有助于为输入病例以及潜在的后续二次传播的风险评估和决策提供信息。由于我们的方法利用了易于获取的旅行者数据作为代理分母，哨兵旅行者监测可以成为其他国家可考虑实施的实用监测工具。
