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The Aedes aegypti mosquito (shown), which is not found in Japan, is dengue's principal vector.

The Aedes aegypti mosquito (shown), which is not found in Japan, is dengue's principal vector.

James Gathany/Wikimedia Commons

Dengue emerges in Japan for first time in decades

TOKYO—After reporting the country's first domestically acquired case of dengue fever in nearly 70 years yesterday, Japan's health ministry today confirmed finding two more patients. The initial patient, a girl in her teens, had a sudden onset of high fever on 20 August and was hospitalized in Saitama City, near Tokyo. Hospital staff, suspecting dengue, on 26 August sent blood samples to the National Institute of Infectious Diseases in Tokyo, which confirmed the diagnosis.

An epidemiological investigation turned up two more patients. All three are students at the same school in Tokyo and are members of a dance group that regularly practices in a city park, leading the ministry to conclude that students were infected in the park.

Dengue is widespread in the tropics and subtropics. According to the ministry, about 200 Japanese contract the mosquito-borne viral disease each year while traveling overseas. But none of the three patients had traveled overseas. A German woman apparently acquired the virus during a trip to Japan last September. After returning to Berlin, she was hospitalized for an acute fever and rash. Blood tests later confirmed a dengue infection.

The dengue virus's principal vector, the Aedes aegypti mosquito, is not found in Japan, but the tiger mosquito, Aedes albopictus, can also host the virus and is common throughout much of the country. The ministry played down the risk of an outbreak.