<p>In 2014, an outbreak of dengue fever occurred in the Tokyo metropolis for the first time in approximately 70 years. Since then, more than 200 imported dengue cases have been reported each year, in parallel with an upsurge in the number of overseas visitors into Japan. Therefore, the risk of an outbreak of dengue fever remains unchanged. On September 2, 2019, a drill for an Aedes-borne virus outbreak was conducted in the Shinjuku Gyoen National Garden. In the drill, mosquitoes were collected in the Garden and examined for the presence of Aedes-borne viruses. However, no viruses including dengue virus were detected in the mosquitoes. This review presents the results of the virus detection drill and discusses the possibility of establishment of persistent DENV transmission cycles in Japan from the aspect of the viral ecology.</p>