Back-of-the-envelope Delta variant math [View all]

[Shermann]

I'm working off of this article:

https://www.cidrap.umn.edu/news-perspective/2021/06/cdc-delta-variant-now-10-us-covid-19-cases

So on May 22 the variant made up 2.7% of US cases (approx 750 out of 28,000).

Now the variant makes up 10% of cases (approx 1200 out of 12,400).

So despite the number of CV-19 cases going down, Delta cases are doubling every four weeks. If you think of the Delta variant as an independent pandemic, that gives it an R-naught value of around 1.4 (assuming a two week infectious period). That is significantly higher than the magic value of 1 that you must remain below for the pandemic to wane.

That's during a time where the vaccines are in effect, but vaccinations are trailing off. So in looking at it independently from other strains, it appears to be a pandemic within a pandemic that will continue to spread with exponential growth.

Please find a mistake in my math or reasoning.