Dengue Fever

by Kensatsukan Gaijin

If you are gearing up for a trip to Tokyo soon, you might want to pack one more thing in your suitcase - mosquito repellant.  For the first time since 1945, Japan is suffering under an outbreak of Dengue Fever.  The number of locally acquired dengue fever cases reported in Japan is now up to 144, as of Friday. The first locally transmitted case in 70 years was reported in a teenage girl from Saitama Prefecture one month ago.  


Due to the spread of the disease, Tokyo authorities have been undertaking disinfection works, closing the popular Yoyogi Park and Shinjuku Central Park. Restrictions have also been placed on visits to Aoyama Park, Sotobori Park and Meiji Jingu Gaien Park. Now the health ministry says a case of dengue fever is now suspected in Tokyo’s Sumida Ward, relatively far from the suspected epicenter of a recent outbreak of the disease. 


Japan is not alone - the fever is spreading around Asia, and on Friday in China, medical authorities in heavily-populated Guangdong Province reported a spike in infections, from 6,083 to 8,273, in just two days.  This year's outbreak is 14 times greater than last year, a result, medical authorities say, of heavy rains across southern China. With larger amounts of standing water, the breeding ground for the disease-carrying Aedes aegypti mosquitoes, insect numbers have exploded.  


Spread by mosquitoes, dengue is one of the leading causes of death in the tropics.  The dengue virus is transmitted by tiger mosquitoes — whose habitat in Japan ranges as far north as Tohoku. If they bite infected people, the virus multiplies inside them and gets transmitted to other people when the mosquitoes bite them. Also known as "breakbone disease" for the extreme joint pain it induces, pain behind the eyes, rashes, easy bruising, and headaches are hallmarks of infection. A more extreme variant of the virus, dengue hemmorhagic fever, causes vomiting of blood and is often fatal. Every year, around 50 to 100 million dengue infections are registered all over the world with a mortality rate of around 2.5 percent.  


There is no immunization or specific treatment for dengue fever. Fortunately, there is hope:  the Japanese pharmaceutical company Takeda is developing a vaccine against dengue fever that is expected to be marketed in 2017.  The vaccine, still in an experimental phase, uses a live weakened virus of the mosquito-borne disease and is the work of the US company Inviragen which was acquired by Takeda in 2013.  French pharmaceutical company Sanofi is also developing a vaccine against dengue which is already in its final stage of testing with an estimated release date of 2015.  


In addition, a low-priced device that can collect up to 500 mosquitoes in three hours has been developed by a former university professor in Nagoya that only costs 3,000 yen.  The black, triangular-shaped device measures about 40 cm long and is made from waterproof plastic cardboard. To a mosquito, the shape of the device resembles a crouched dog or cat.  It has a replaceable adhesive sheet attached to its surface that emits a smell similar to animals or human beings, drawing and trapping mosquitoes.  Since the summer people have already purchased 500 of the item.  Most experts believe that the only way to successfully stop this disease is to control mosquito populations and reduce the amount of people exposed to and bitten by tiger mosquitos.