The Re reported yesterday by the university of Tennessee dashboard was 1.06 and the R0 widely reported at the beginning of the pandemic was 2.5. If we plug in those values and solve for Pi for the state of Tennessee we get 0.576. (1.06/2.5) = (1 – Pi). 0.424 = (1 – Pi). Pi = 0.576.
The number of actual cases according to the CDC is far more than the number of reported cases, around 10 times more according to the CDC’s best estimate.
The general estimate at the start of the pandemic was we would have to get to around 60% immunity in the community for the virus to die off due to herd immunity. If the data being reported is anywhere in the vicinity we could be at 57.6% immunity in the state as of yesterday.
Once Re gets below 1.00 the number of new cases will be declining as the number of active cases which spawn new infections will also be declining.
On July 16th, I suggested we probably needed to get to around 115k reported cases in the state to hit our HIT (herd immunity threshold). There’s a technical glitch at the state level in today’s report but they do provide the total number of known cases as of today and it’s at 99,044.
My estimate was a best guess at the time but we’re only 16k away from the number so I still think in the next few days Re will likely go below 1.00 for the state. If so, no one should expect the virus to die out overnight but it will start to decline fairly rapidly as it will have difficulty finding new hosts until there are very few prospects left.
Lastly, this is a new virus and while our professionals and scientists know a thing or two about viruses in general, they need specific data to know everything there is to know about any new virus. In the beginning of something like this and for some time everyone, including the best minds we have, will be operating to some degree in the “fog of war”.
My big concern with our data right now continues to be that with the various “artificial” means we’re undertaking to slow the spread of the virus and with certain estimates that have been provided by those who should know best the conclusions one might draw from that data and the underlying assumptions could potentially turn out to be quite erroneous.
Note: I am not a doctor, nor am I a scientist. By profession, prior to my retirement, I was a project controls engineer, which means I collect and analyze data. More importantly perhaps, over the course of my life, I’ve stayed at a Holiday Inn Express on multiple occasions. TIFWIW.
