Dengue Sentinel Traveler Surveillance: Monthly and Yearly Notification Trends among Japanese Travelers, 2006–2014

Abstract

BackgroundDengue 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.MethodsUsing 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.ResultsThere 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.ConclusionTravelers 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.

Epidemiological Characteristics and Risk Factors of Dengue Infection in Korean Travelers

“…However, dengue patients aged 20–49 years accounted for 75.2% of total imported cases in Korea ( P < 0.001). Similarly, dengue cases aged 20–39 years occupied about 60% of total imported cases in Japan (51). Such distribution is different from those in dengue-endemic countries.…”

“…Note that each graph displays data with different scales on the number of reported cases and age distribution. Data for Philippines (2009), Thailand (2010) and Japan (2006–2014) were collected from national surveillance reports and previously published studies (3214851). …”

“…Specially, infected males (n = 411) were 1.5 times more than females (n = 261) in the 20–49 year age group. Similarly, more dengue cases were reported for males than for women in Korea and Japan during 2006–2010 (51). A previous study also showed that there was a predominance of males with DENV infection in six Asian countries (Lao PDR, Philippines, Singapore, Sri Lanka, Cambodia, and Malaysia) (52).…”

Assessing dengue control in Tokyo, 2014

“…Japan is in a temperate zone and dengue is not endemic in the country. However, Japan has experienced a steady increase in the number of imported cases, mainly from South and Southeast Asian countries [15][16][17]. Despite only sporadic abundance of Aedes aegypti, the species Aedes albopictus is widespread across Honshu Island and all western parts of Japan, theoretically allowing for chains of dengue transmission to exist [18][19][20][21][22][23].…”

An interdisciplinary study: disseminating information on dengue prevention and control in the world-famous travel destination, Bali, Indonesia

“…The insufficient knowledge and action amongst international travellers might partly explain why other countries such as Italy (Rovida et al 2011;Zavattoni et al 2016), Japan (Fukusumi et al 2016;Yoshikawa 2011) and Australia (Ernst et al 2015;Warrilow et al 2012) continue to report dengue cases amongst travellers returning from Bali.…”