A woman who is suing Usher for allegedly exposing her to genital herpes has come forward, saying Usher cherry-picked her out of a crowd at one of his concerts, got her number, went to her hotel and had sex with her without disclosing he allegedly had genital herpes.

Quantasia Sharpton appeared with celeb lawyer Lisa Bloom Monday morning, saying she was celebrating her 19th birthday at an Usher concert, wearing a birthday crown, when she was contacted by Usher's security.

Sharpton says she's negative for herpes but still feels violated.

THERE MAY BE MORE COMING
TMZ.com

Bloom went on to say she doesn't know for sure if Usher has herpes but there are media reports saying just that and he has remained silent. 

Bloom is filing a lawsuit on behalf of 2 women and 1 man, all of whom claim they have had sexual contact with Usher since his alleged diagnosis. She says 1 of the remaining clients -- either the man or woman -- has tested positive for herpes.

Attorney Bloom went on to say she's been contacted by others and may file additional lawsuits.

Bloom says one of the things she wants is a court order forcing Usher to reveal to his future sex partners that he has an STD ... again, his health status has not been confirmed.

We've reached out to Usher's reps ... so far they're mum.