(CNN) A CNN investigation of 17 Trump campaign rallies finds that 14 of the host counties -- 82% of them -- had an increased rate of new Covid-19 cases one month after the rally.
The 17 rallies occurred between August 17 and September 26. CNN evaluated the rate of new daily cases per 100,000 residents at four weeks before the rally, on the rally date, and four weeks after the rally at the county level and at the state level.
Of the 14 host counties that had increased infection rates, eight of the counties had declining rates of infection in the month before the rally. The other six counties already had increasing rates of infection in that preceding month.
CNN's analysis also found that in 10 counties, the new rates of infection were growing faster than the overall rate for the state.
Some of the rallies that were surveyed included the Trump campaign's September 12 rally in Minden, Nevada.
In the month before the rally, cases had begun to fall. But four weeks after the event, the rate of new cases in the county skyrocketed by 225%, outpacing the 74% increase the rest of the state experienced in the same time period.
CNN also looked at the September 18 rally in Bemidji, Minnesota and found that while rates of infection had already been increasing in the month prior to the rally, the rate of infection in the county one month later had jumped by more than 385% and was greater than the state's rate of infection.
CNN's analysis evaluated rallies in Minnesota, Wisconsin, Arizona, Pennsylvania, New Hampshire, North Carolina, Michigan, Nevada, Wisconsin, Minnesota, North Carolina, Ohio, and Florida.