DR. SANJAY GUPTA: CNN investigated what happened at 17 recent Trump rallies, specifically looking at infection rates in the counties where the rallies took place, four weeks before and four weeks after. And then also comparing them to the corresponding rates at the state level.

The results were startling. 82% of the time, the rate of new cases in the county jumped after President Trump's visit. More than half the time, the county rate of new cases grew faster than the state's rate.

For example, September 12th, Minden, Nevada. In the month going into that rally, cases had begun to fall. But fast forward four weeks and the rate of new cases in the county skyrocketed by 225%, far outpacing the 74% increase the state experienced. Or September 18th, Bemidji, Minnesota. Rates of infection were already climbing in the month before the rally. By the day of the rally, the rate of infection was 6.36 for every 100,000 people in the county, about half the rate of Minnesota. But a month after the rally, the rate of infection in the county had jumped 385% and quickly bypassed the state's rate of infection.

Here’s another way to think about it. If you attend a gathering like this, according to new research, in most places in the United States, there is now a 99% chance the virus is attending right alongside with you.