Global warming may bring dengue fever to Hokkaido

Kyodo News

Global warming could bring dengue fever to the northernmost reaches of Japan by expanding the habitat of mosquitoes, which transmit the virus, a recent study by the National Institute of Infectious Diseases shows.

The disease, also known as breakbone fever, usually creates an epidemic in Southeast Asia and other tropical areas, but it may even enter Hokkaido by the end of this century if local temperatures rise enough for mosquitoes to thrive, a research group at the institute said.

One thing feared by the advance of global warming has been an expansion in the habitat of the tiger mosquito, which currently reaches Akita Prefecture, about 200 km south of Hokkaido’s southernmost tip, the group said.

Mutsuo Kobayashi, a member of the group, said it is impossible to prevent the expansion in tiger mosquitoes and dengue patients. “It would be better for us to remove the mosquitoes,” he said.

Tiger mosquitoes usually live in areas with an average annual temperature of 11 or higher. The average temperature in Hokkaido was 8.8 in 2003.

In 1950s Japan, the northern limit of tiger mosquitoes was Tochigi Prefecture, roughly 400 km south of Akita.

Rising temperatures and commodity distribution systems keep pushing the limit northward, the group said.

The research team projects global warming will continue to push up temperatures in north Japan.

Between 50 million and 100 million people develop dengue fever each year in tropical and subtropical areas, and dozens of Japanese often bring it home with them.