The risk of imported infectious diseases such as dengue fever occurring in Japan has increased recently due to the number of people traveling internationally and other similar reasons. Dengue fever and the Zika virus are both mosquito-borne infections, and are reportedly at epidemic levels in Southeast Asia, Central and South America.
To reduce the threat of infectious diseases, measures to control mosquitoes are essential. Shinjuku City’s mosquito countermeasures include removing insect larvae from rainwater drains on streets and at parks and mowing the grass at parks. Let’s all take similar countermeasures to help prevent mosquitoes from breeding near our homes and places of employment.

Mosquitoes in Japan That Transmit Viruses

Asian tiger mosquitoes, which transmit both dengue fever and the zika virus, can be found in most areas across Japan (the island of Honshu and southward, excluding Hokkaido). These mosquitoes are active mainly from mid-May through the end of October, and suck blood between morning and evening.

Asian tiger mosquito
Photo courtesy of the Department of Medical Entomology of the National Institute of Infectious Diseases

Diseases Transmitted by Mosquitoes

♦︎ What Is Dengue Fever?
Dengue fever is a disease that is spread when a mosquito drinks the blood of a person infected with the dengue fever virus and then bites another person. It is not transmitted directly from person to person.
While not all people become ill from the virus, its symptoms include fever, headaches, aches in the joints and skin rash. The symptoms typically continue for about a week.

♦︎ What Is the Zika Virus?
The zika virus is primarily spread by mosquitoes.
The symptoms include a slight fever, skin rash, conjunctivitis, muscular pain, aches in the joints, fatigue and headaches. However, even if you are infected, the zika virus may be hard to detect because the symptoms may be very slight or not appear at all.
Because a zika virus infection during pregnancy can cause congenital disorders in the fetus such as microcephaly, expectant mothers and those who may be expecting should refrain from going to areas with a high risk of infection.

Mosquito Countermeasures

♦︎ Eliminate Water Puddles
Asian tiger mosquito larvae breed in small water puddles in potted plant saucers, weather-beaten buckets and plastic PET bottles, old tires, hollows of plastic leisure sheets and rainwater drains. Always keep containers and other items that collect rainwater dry and empty by turning them upside down once a week. Keeping rainwater containers clean and tidy is also a good idea.

♦︎ Cut Thickets and Pull Weeds
Asian tiger mosquitoes thrive in humid places where there is little sunlight and lots of plants. It is wise to prune trees and bushes and mow your lawn.

To Prevent Mosquito Bites

・If you are going to visit a place that has a lot of mosquitoes, wear a long-sleeved shirt and long pants so that your skin is not exposed.
・Be sure to properly use insect repellent and mosquito-repelling incense to prevent insect bites when necessary.
・Install screen doors on your windows, and make a habit of quickly opening and shutting doors, entrances and windows to prevent mosquitoes from entering your home.

April 25, 2018