The individuals that originated the urine samples likely have some very nasty disease(s) and handling the containers could possibly transmit said disease(s).
The containers should be disinfected on the outside. That is a requirement for shipping potentially hazardous samples.
It takes something like Ebola, or at least the world’s worst STD or UTI to make urine infectious.
Any box I see that says “clinic” or medical” or “biological” doesn’t get opened. But it’s safe to go through ordinary shipping and it’s safe to sit there until it gets picked up again.