Organisms not present in body fluids for 72 hours
Welcome to HCM.
Thanks for posting your query.
STDs are more than 30 in number. Certain STDs like gonorrhea
can become infectious within few hours after the infection as it confined local area of genitals.
But infections like HIV
spreads through exchange of body fluids. In HIV, disease gets established only after 72 hours usually. Then only virus would be present in blood,semen or vaginal fluid. So theoretically your girl friend would not get infections that can spread through exchange of body fluids whereas STD affect local tissues of genitalia may be infectious from the hour one itself.
But Medicine is not Mathematics to get constant answers. Deviations can not be ruled out. I hope that you got the point.