Timely estimation of the current value for COVID-19 reproduction factor R has become a key aim of efforts to inform management strategies. R is an important metric used by policy-makers in setting mitigation levels and is also important for accurate modelling of epidemic progression. This brief paper introduces a method for estimating R from biased case testing data. Using testing data, rather than hospitalisation or death data, provides a much earlier metric along the symptomatic progression scale. This can be hugely important when fighting the exponential nature of an epidemic. We develop a practical estimator and apply it to Scottish case testing data to infer a current (20 May 2020) R value of 0.74 with 95% confidence interval [0.48−0.86].
@article{arxiv.2005.12252,
title = {COVID-19: Nowcasting Reproduction Factors Using Biased Case Testing Data},
author = {Carlo R. Contaldi},
journal= {arXiv preprint arXiv:2005.12252},
year = {2020}
}