The Japan dengue fever outbreak has risen to 87, with the first case reported outside of Tokyo, Japanese health officials said today.

Image/CDC
Image/CDC

The Japan Times reports today that a man who lives in the city of Chiba, on the outskirts of Tokyo, is he first person in the current outbreak of dengue fever to be infected outside of the capital. The victim is a 60 year old man, who has not traveled abroad.

The man developed symptoms on Aug. 31 and was hospitalized on Sept. 2. His infection was confirmed Monday. Although hospitalized, he is in a stable condition.

Dengue is an infectious disease caused by the dengue virus (DENV). There are 4 serotypes called DENV-1, DENV-2, DENV-3 and DENV-4. Infection with one serotype produces lifelong immunity against that serotype reinfection. Successive infection with two different serotypes is a risk factor for developing the severe forms of the disease, according to the Pan American Health Organization.

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The Aedes aegypti and Aedes albopictus mosquitoes are transmitters of dengue. The Aedes aegypti female mosquitoes are the main source of dengue transmission. These species bite during the day, with the most active feeding period 2 hours before and after dawn and dusk. The mosquito bites an infected person and ingests blood with the dengue virus, which incubates in the mosquito for a period of 8 to 12 days, after which the mosquito begins to transmit the virus biting others. The newly infected person may have symptoms after 5-7 days of infection.