Mia Dearden is the second DC Comics character to act as Speedy, the sidekick for the Green Arrow. A former sex worker on the streets of Star City, she was saved from her pimp by Green Arrow; became his ward and, eventually, the new Speedy. When Arrow learns of her HIV status, he actually wants to force her to stop fighting crime due to her diagnosis, but she persuades him otherwise.
After years of service with Arrow, Arrow suggests Speedy should join the Teen Titans (a younger group of heroes who fight crime together led by Batman sidekick Robin). She is nervous about revealing her status to the fellow heroes.
In other media besides comic books, Mia was a recurring character on the comics-based television drama Smallville, though her HIV-positive status was never mentioned. In the current TV series Arrow, Mia is not a character, though a character named Thea Dearden Queen has been introduced whom Arrow has nicknamed "Speedy." There has been no mention of HIV there, either.