I have been bitten by a mosquito. i feel rather tired &dizzy and my wrist and forearm aches . i also have diarrhea. is it possible that i have dengue?

I doubt it: But i would worry more about the west nile virus. See your primary care doctor soon.

Dengue fever: Symptoms of dengue can include a high fever; joint, muscle or bony pain; severe headache &/or eye pain; rash and signs of bleeding like bruising easily, bloody nose or gums, or red petechiae on skin. I wouldn't conclude that this is Dengue based on the current symptoms. However, do seek medical eval if symptoms aren't resolving.