US Infections Go Super-Exponential

The seven-day average number of days-to-double in the United States dropped to 2.03 from 2.36 a few days ago. The days-to-double keeps dropping, making the infection curve super-exponential.

If each infected person sickens one additional person every two days, the total number infected would double every two days, and we’d have exponential growth. Super-exponential growth happens if the time to infect the next person decreases every day.

The difference between the confirmed infection counts and the actual counts could explain the super-exponential growth. As the testing increases, we are doing a better job uncovering the underwater part of the iceberg which is the infected, but uncounted. If so, we should see the super-exponential growth fade to exponential, and then sub-exponential as the testing rate stabilizes, and the containment measures take effect. We would see this in the log-plots as a transition from bending-up to straight-line to bending-down, and the dashed line dropping below the dotted line.