I grew up in the Caribbeans and I got dengue once and 2 of my siblings did as well. It was not considered a big deal (at least not fatal) - We talked about it like a bad flu. I remember a bad week-long fever, headache, pain behind the eyes and I couldn't eat anything for days because I had a really bad nausea and I felt disgusted by food.

I think probably the people whose ancestors lived there for hundreds of years (as mine did) probably became immune to all these nasty mosquito-borne diseases through natural selection. Dengue sounds really serious when I read about it now.