There are 4 (or is it 5) strains of DF. You can only get each one once, but each subsequent infection raises the prospect of developing Dengue Hemorrhagic Fever - nasty!
Read more abiutDF here: https://www.worldnomads.com/travel-safety/worldwide/what-you-need-to-know-about-dengue-fever
There's a very strong El Nino effect occurring this year 2015, and scientists are predicting a very bad year for DF throughout the tropics. That's already becoming evident with epidemics in Myanmar for example. Even Hawaii is experiencing a larger than usual number of cases (112 and rising).
Take care, use the precautions outlined in the article I've linked you to. almost 3 years ago