I'm surprised the international community hasn't built a few walls/fences to contain threats like those.
It's pretty hard to build a rat proof fence, especially across hundreds or thousands of miles, and it is an "outbreak" concern more than anything, it doesn't infect many people:
https://www.cdc.gov/poxvirus/monkeypox/about.html
The reason they are trying to trace it is that every human infection is an opportunity for an adapted, transmissible virus to emerge.
If you’re interested in reading about the initial cases of various emerging diseases (or rather, emerging diagnoses), Laurie Garrett‘s book, The Coming Plague, is a good read.