Prairie Dogs.
When I was young we had a farm in NE New Mexico. We left there in 1052. On a visit back in 1985 I noticed the place had been taken over by Prairie Dogs.
A few years later I noticed a plague warning on a map right over that spot.
From what I have read in the past, the Americas were plague free until Chinese were brought in for laborers. When plague broke out in China Town in San Francisco the City Fathers refused to do anything about it and allowed it to spread.