Infectious Disease is often an elective that can be done during your 4th year (or maybe 3rd year if your school offers 3rd year electives)
If your school isn't affliated with a hospital or group of hospitals, then you may have trouble finding an ID rotation (if you're not a 4th year student). As a 4th year, you can do visiting student electives almost anywhere you want (and in ID if you want)