Not so. Inmates are going in and out all the time to offsite court dates (where they’re held in the county jail for as long as it takes) or specialist medical appointments or needed procedures. Now we’ve cut those down to the absolutely necessary trips, but our cancer patients still need their radiation treatments, emergency room visits are needed to evaluate chest pains, etc.
I won’t deny staff is a likely source for infections coming in, though. Staff resistance to required protocol is something I’ve observed. Covid denial is not a small issue in my state. Many hospitals and medical clinics in the area have the same issues with their employees. They too mandate masks etc. onsite, but a lot of folks go home, then go out to the bars or the family gatherings, or church on weekends.
I’m amazed we skated covid-free for 6 months, and that was due to aggressive quarantine and other recommended measures, but all it takes is one super-spreader/shedder to trigger a spread.