1. A pneumonia outbreak associated with a new coronavirus of probable bat origin;Zhou;Nature,2020
2. World Health Organization. WHO director-general's opening remarks at the media briefing on covid-19. 11 March 2020:https://www.who.int/dg/speeches/detail/who-director-general-s-opening-remarks-at-the-media-briefing-on-covid-19 —11-march-2020.
3. Clinical features of covid-19;Vetter;BMJ,2020
4. COVID-19 deaths worldwide per million population as of April 30, 2021, by country:https://www.statista.com/statistics/1104709/coronavirus-deaths-worldwide-per-million-inhabitants/.
5. Federal Statistical Office of Germany (Statistisches Bundesamt, Wiesbaden) – DESTATIS. Gesundheit. Grunddaten der Krankenhäuser; Fachserie 12, Reihe 6.1.1. Krankenhäuser 2017, 2.8,2019