ST. LOUIS — Missouri has the third-highest rate of COVID-19 transmission of any state in the country according to Rt.live, a COVID-19 tracking system developed by the founders of Instagram.
Rt.live's model said Missouri has an Rt estimate of 1.13 as of Aug. 5. Only Nevada(1.16) and Hawaii(1.36) have higher rates than Missouri, according to the analysis.
Reproduction factor — also known as R0(pronounced "R Naught") or Re — measures the transmission level of the infections. An R0 of one means each person who tests positive spreads the virus to one other person. An R0 of more than one means the virus is spreading exponentially and an R0 of less than one means transmission of the virus has been interrupted and slowed down.
Rt works on the same scale as R0, but is a slight adjustment on the reproduction factor that its creators say adjusts for changes in testing.
"Our model attempts to correct for testing by looking at what is essentially the positivity rate. This positivity rate changes over time because the group of people tested changes," the site's frequently asked questions section says. "If anything, our model may understate Rt currently because far more people without symptoms are tested, thus driving the positive percentage down and overstating a downward trend in cases."
The co-founders of Instagram — Kevin Systrom and Mike Krieger — worked with Tom Vladeck, a data scientist and owner of Gradient Metrics, to develop the project, which is not affiliated with Instagram or Gradient Metrics. They said they created the site to help people understand the relative growth or decline of the virus.
Missouri's Rt estimate has remained at 1.13 since July 20, and was slightly higher earlier in July. Missouri had an Rt estimate under one from April 1 to May 14.
As of Aug. 5, Illinois — which has seen an increase in cases since loosening restrictions — has an Rt estimate of 1.07, which is the eleventh-highest in the country. Illinois had an Rt estimate under one from March 30 to June 13.
As for the St. Louis area, in particular, the St. Louis Metropolitan Pandemic Task Force calculates R0 for portions of the St. Louis area. On Monday, the last time the task force provided the R0 data, Dr. Alex Garza said the area's R0 was about 1.26.
The creators of Rt.live said they think their formula does a good job of boiling a complex topic into one number, it is important to look at other data as well.
"While we believe our model is very strong, all models have limitations because they reduce a complex reality into a simple system," the site says.