Covid in 80% NA deer and they could spread it to humans

No.13848107 ViewReplyOriginalReport
An unpublished study has detected the virus in 80% of deer sampled in Iowa between November 2020 and January 2021.

https://www.walesonline.co.uk/news/uk-news/covid-up-80-white-tailed-22109219

HOW did deer get this from the plague rats?