Estimate of the development of the epidemic reproduction number Rt from Coronavirus SARS-CoV-2 case data and implications for political measures based on prognostics

Sahamoddin Khailaie; Tanmay Mitra; Arnab Bandyopadhyay; Marta Schips; Pietro Mascheroni; Patrizio Vanella; Berit Lange; Sebastian Binder; Michael Meyer-Hermann

Outbreak of the novel Coronavirus SARS-CoV-2 (CoV) in China has induced a world-wide pandemic. The comparably high lethality in the elderly population and in patients with comorbidities (Istituto Superiore di Sanità 2020), together with a widely absent immunisation of the population against the novel virus as well as the limited health system capacity, which was estimated to become overwhelmed by an unlimited virus spreading (an der Heiden and Buchholz 2020), led to non-pharmaceutical interventions (NPIs) to reduce virus transmission mostly by reducing inter-individual contacts. The aim of these measures was to achieve at least a delay of viral spreading, allowing the health care system to extend its capacities and to treat less patients per time. The measures might also induce a complete stop of viral spreading. The NPIs installed in Germany appeared to be efficient in containing viral dissemination. Any measure impacts on the observed numbers of new infections with a delay in the range of the serial interval, which is in the range of 4.5 days for CoV (Nishiura et al. 2020; Flaxman et al. 2020 ) and makes it difficult to judge when to release NPIs. In view of collateral damages and economic burden, the pressure to release NPIs as early as possible is increasing (Dorn et al. 2020 ). Thus, current political decisions require a safe ground providing an estimate of the impact of NPIs by now. In fact, a continuation of daily increase of reported cases while the measures are in place can also mislead political decisions if not well informed about the present trend of the achieved reproduction number. Furthermore, the high variance of the locally reported new cases adds to the uncertainty about the efficiency of the NPIs. Thus, it is extremely important to construct a model that captures not only the disease dynamics but also has the potential to inform us about the trend of the outbreak by considering the timedependence of the reproduction number for COVID-19. The situation in Europe was recently analysed (Flaxman et al. 2020 ). Here, a systematic analysis of the development of the reproduction number over the time period of the CoV-outbreak in Germany and in all federal states of Germany is provided by the date of paper submission.