text:  U.S. futures contracts are trading lower at this hour. Dow futures down one-tenth of a percent. This is NPR. Dengue, the mosquito-borne illness, causes flu-like symptoms, but a new study suggests it's also associated with an increased risk of depression. NPR's Gabrielle Emanuel has more. The risk of developing depression is almost double in the first few months after getting dengue compared to normal. That risk goes down but remains elevated even after a year.