Urethritis can be picked up from many things where bacteria is present.
It can take up to 2 weeks to clear but should notice the symptoms lessening after a couple of days.
Thanks. What about the hot tub?
I am sure that it is possible, I can not rule out that it is not possible. In most cases not enough scientific tests have been done to disprove a lot of things. Since a poorly maintained hot tub would have bacterial growth then it is possible, but why would you go into a hot tub like that?
If you suspect her of cheating then I would not let this push you over the edge to accuse her.