text: what causes uti's? i know this is a dumb question and i know you are going to laugh? but a few months ago my cat had one. then a week or so i had one. now my cat and my duaghter both have one! what is it? something in the air? it's caused by a bacteria getting into the urethra and making it's way up he urinary tract.  it's cause by many things including not cleaning properly.  it's can also be caused by sex, that's why it's always a good idea to urinate after sex.  you could have also taken an antibiotic that caused the uti, that's a pretty common way.