Japan mobilises against dengue fever in Tokyo

An official at the Tokyo metropolitan government sets a mosquito trap in Yoyogi Park in Shibuya Ward, Tokyo. The trap contains dry ice, which emits carbon dioxide, to lure the insects.
PHOTO: Japan mobilises against dengue fever in Tokyo

TOKYO - Steps are being taken at Yoyogi Park in Tokyo's Shibuya Ward against dengue fever as the number of confirmed infections in the nation continues to climb. In the park, where visitors reportedly contracted the infection, pond water in which mosquitoes might breed was drained, and signs urging people to protect themselves against the insects were set up.

Long sleeves, long trousers

On Monday, workers started to drain pond water around 4 pm. It is expected to take about two days to drain all the water. Workers wearing helmets with mosquito netting vacuumed water out of ditches. Operations to exterminate mosquitoes were not conducted on this day, but the Tokyo metropolitan government will continue monitoring the park.

Some people who use the park worry about safety. A 22-year-old male university student, who came from Suginami Ward, Tokyo, and practiced dancing with his friend there, said with concern: "I visited the park because precautions such as spraying insecticides are being taken. Today, I put on a long-sleeve shirt, which I usually don't wear."

Along park roads, 90 signs were set up, warning, "Be careful of mosquitoes!" and "Please avoid wearing open-toed sandals." The signs urge people to wear long-sleeve shirts and long trousers and use insect repellent.

No. of park visitors drops sharply

Dengue fever is also affecting events to be held in the park. According to the metropolitan government's park management division, a flea market and a bicycle lesson for children set for Saturday were cancelled. Though some events have gone ahead as scheduled because a voluntary ban on use of the park has not been issued, the number of park visitors reportedly sharply decreased since the infections were confirmed.

A woman in her 50s, who works at a park stall, said she lights a mosquito coil every day and applies insect repellent, which she had not used before now. "Of course, the current bad weather has partly affected sales, but they are not recovering [due to fear of the disease]. I hope the park will return to normal, where people can play at ease," she said.

Ministry urges calm over spread of disease

The Health, Labor and Welfare Ministry called on people to remain calm about the spread of dengue fever and said infections were on a limited scale, although new cases have been confirmed.

"The infections are limited to a specific area, and the disease is unlikely to become widespread," a ministry official said.

The ministry believes infections are limited because tiger mosquitoes, which transmit dengue fever, generally live within a 50-to-100-metre range.

The lifespans of the mosquitoes are 30 to 40 days, and during that time, a mosquito is said to bite a human four times, at maximum.

The mosquitoes are only active between mid-May and late October and cannot survive the winter. Medical experts believe dengue fever is not passed on to the next generation of mosquitoes either.

Officials at the Tokyo metropolitan government have been checking mosquitoes in Yoyogi Park, where the patients are believed to have become infected with the disease, but no mosquitoes have been found carrying the virus.

However, Tomohiko Takasaki, chief of the Department of Virology I at the National Institute of Infectious Diseases, said: "If the viruses are found in one out of every 100 mosquitoes, it's an outbreak. That's a nerve-racking thought, though the viruses have yet to be found in the mosquitoes."

Kyoko Sawabe, chief of the institute's Department of Medical Entomology, added: "There may be some people who have become infected but do not show symptoms and are unaware of the infection. Therefore, it's possible that the viruses could spread from these carriers via mosquitoes. Thorough research and measures to cope with the disease are needed."