Does a urinary tract infection affect the behavior of an Alzheimer's patient?

Absolutely. Is your wife on antibiotics?

Any time an elderly person's behavior changes suddenly they should always be tested for a UTI.

Yes. As a full time caregiver and having trained to be a professional in home caregiver, I learned to be very watchful for UTIs. Far too many patients syffer from these without diagnosis. Behaviors can change drastically. Call the primary care doc and get a urine test immediately. Good luck.