Some people call squirrels – big eyed rats with fussy tails, others call rats – baby squirrels that haunt the night. I say they are rodents that transmit diseases. Both rodents can carry the plague – yes the one from the medieval ages, the deadliest infectious disease. Squirrels are also know to transmit tularemia ( very high fatality rate), typhus and ringworm through bites or other forms of direct contact, like feces. Then there are rats, these little night devils can carry even more diseases including hantavirus, leptospirosis, lymphocytic choriomeningitis, and salmonella. So you ask which one of these vermin is worst when it comes down to transmitting diseases, well on a scale of 10, rats are 9/10 and squirrels are 8/10 (mostly because the high fatality rate of tularemia).
https://gogreenpestcontrol.ca/squirrel-vs-rats…s-and-whos-worst/
https://www.linkedin.com/pulse/squirrels-vs-rats-diseases-whos-worst-randy-bilesky/?published=t