How is the R-Factor estimated?
The approach is based on computations of AGES (Austrian Agency for Health and Food Safety) where the effective reproduction number is estimated via the time series of new infections and the serial interval, the average duration between the disease onset of individual i and the disease onset of other individuals, caused by individual i. The serial interval was estimated to have a mean of 4.46 and a standard deviation of 2.63. An Rt of 0.5 would mean that the number of new infections would halve within 4.46 days.
Thus, while an Rt <1 means that the number of new infections is contracting and expected to abate, an Rt >1 represents rising new infections and is an indicator for governments to tighten measures against COVID-19.
Please note that the presented estimates of Rt can deviate from numbers published by other institutions, such as figures by the Robert Koch Institute for Germany, due to differences in the computational approach described above, the fact that R is estimated on a weekly sliding window and deviations in the data source.
Datasource New-Infections: John Hopkins University