Coronavirus Covid-19 increased by 467 percent in Kansas counties, requiring masks in public places. The number of cases fell within six weeks of the mandate, according to the CDC. The study looked at the disparities between the Kansas counties in the summer. Some counties that did not need masks had less strict instructions, according to the report. The CDC reports that the rate of Covids-19 cases has primarily been reversed after the mandate has been enforced.

Reference
CDC says mask mandates can slow Covid-19 spread. https://www.nbcnews.com/health/health-news/cdc-says-mask-mandates-can-slow-covid-19-spread-n1248417?cid=eml_nbn_20201120