TY - JOUR TI - Real-time estimation of R0 for COVID-19 spread AU - Simos, T.E. AU - Tsitouras, C. AU - Kovalnogov, V.N. AU - Fedorov, R.V. AU - Generalov, D.A. JO - Trends in Mathematics PY - 2021 VL - 9 TODO - 6 SP - null PB - MDPI AG SN - null TODO - 10.3390/math9060664 TODO - null TODO - We propose a real-time approximation of R0 in an SIR-type model that applies to the COVID-19 epidemic outbreak. A very useful direct formula expressing R0 is found. Then, various type of models are considered, namely, finite differences, cubic splines, Piecewise Cubic Hermite interpolation and linear least squares approximation. Preserving the monotonicity of the formula under consideration proves to be of crucial importance. This latter property is preferred over accuracy, since it maintains positive R0. Only the Linear Least Squares technique guarantees this, and is finally proposed here. Tests on real COVID-19 data confirm the usefulness of our approach. © 2021 by the authors. Licensee MDPI, Basel, Switzerland. ER -