## A. What is Ro?

Ro (pronounced R sub naught) is a basic reproduction ratio, i.e. reproduction rate. In a report, the CDC states that Ro is a modeling term:

“R0 is not a biological constant for a pathogen, a rate over time, or a measure of disease severity, and R0 cannot be modified through vaccination campaigns. R0 is rarely measured directly, and modeled R0 values are dependent on model structures and assumptions.” [Delamater PL, Street EJ, Leslie TF, Yang Y, Jacobsen KH. Complexity of the Basic Reproduction Number (R0). Emerg Infect Dis. 2019;25(1):1-4. https://dx.doi.org/10.3201/eid2501.171901 ]

There are various methods for calculating Ro.  The SEIR model for the equation is:

Ro  = 1+ K (τE +  τI) + K2EτI)

All of the terms in this equation are dependent upon the actual number of infected individuals.  If the number of infected individuals is unknown, then the equation stands without an answer.

Small scale antibody studies show that the number of people infected may be from 7 to 85 times more than the number of people tested.  Hence, no one really knows what the true Ro number is.

Wikipedia states:

“Since R0 is rarely observed in the field and is usually calculated via a mathematical model, this severely limits its usefulness.” https://en.wikipedia.org/wiki/Basic_reproduction_number#Estimation_methods

In a recent publication, the CDC stated that the Ro for the COVID-19 virus is 5.7.  This is based on the doubling time for the tested COVID cases. [https://wwwnc.cdc.gov/eid/article/26/7/20-0282_article  They increased the previous estimate from 2.2 to 2.7.  The World Health Organization estimated Ro to be 3.4.

The current method of determining Ro is flawed in that it requires data that does not exist and may never exist.