The Biomedical and Health Informatics PhD Program is a residential doctoral program. Students complete coursework, as well as a dissertation. Most UWM courses are taught on campus, including some of the required courses of the PhD program; however, UWM does offer many courses in a distance education format where all or part of the course is online. You can find a list of options on the online copy of UWM Schedule of Classes (See http://www4.uwm.edu/schedule/), by selecting the current term and looking at the listings on on the left, under the heading "Distance Education Classes".
In addition, UWM has cooperative agreements in place with the nearby Medical College of Wisconsin and Marquette University.
You are able to take courses at these institutions, with the approval of your advisor, the steering committee, and the instructor at the host institution, with no additional tuition beyond what you pay to UWM. Pat Hayes (firstname.lastname@example.org) will be able to assist you at getting the necessary approvals from off-campus. These partnering schools offer residential, as well as online options.
Be aware that each institution has its own calendar which may not correspond very closely to UWM, so be ready to plan ahead if you decided to pursue any of these options.