Coronavirus Transmission Rate: Best and Worst U.S. States

Which U.S. States Have the Highest and Lowest Coronavirus Transmission Rates? By transmission rate, we're referring to R, the reproduction rate of the virus. Recall that R = 1 means that each infected person infects 1 other person. To slow the virus, R needs to be <1. Currently, it's estimated that only 10 states plus Washington, DC have R<1, while the other 40 states have an R >1.

In especially good shape are states such as Connecticut, bolded below, where the R is well below 1 and there were only 12 new cases per 100,000 people over the past week.

An R slightly below or only slightly above 1, when there are few overall cases, is still quite good–that describes Maine, North Carolina and Kentucky currently, although all will need to be careful to watch their R so as to keep new cases low.

Best U.S. States by Coronavirus Transmission Rate (R)

Connecticut (R = .73), 12 new cases per 100K in last week
Washington, DC (R = .85), 82 new cases per 100K in last week
Massachusetts (R = .9), 120 new cases per 100K in last week
New Hampshire (R = .91), 28 new cases per 100K in last week
Virginia (R = .93), 48 new cases per 100K in last week
Rhode Island (R = .96), 91 new cases per 100K in last week
Maine (R = .98), 8 new cases per 100K in last week
Maryland (R = .98), 54 new cases per 100K in last week
Illinois (R = .98), 56 new cases per 100K in last week
North Carolina (R = .98), 14 new cases per 100K in last week
Kentucky (R = .98), 13 new cases per 100K in last week

At the other end of the spectrum are states such as Nevada, Florida, Idaho and California, all of which have an R higher than 1 and over 100 new cases per 100,000 population over the past week. States such as these have prompted New York and the Tri-State area to Mandate a 14-Day Quarantine for Visitors from High Covid-19 States.

Worst U.S. States by Coronavirus Transmission Rate (R)