On Mar 11th, 2020, the World Health Organization (WHO) stated in its Situation Report - 51 Coronavirus disease 2019 (COVID-19) as a pandemic. In early April 2020, a teaching hospital underwent shutdown and quarantine due to an outbreak of infection in accordance with Section 6 of the Infection Protection Act (index patient and 5 infected nursing staff). The complete staff (physicians, nurses and nonmedical personnel [NMP]) underwent COVID-19 testing within two phases: (1) between Apr 3rd and 5th, 2020 [n=1170], followed by (2) between Apr 8th and 9th, 2020 [n=953] with COVID-19 silent carrier positivity rates in accordance to testing phases of (1) n=19 (1.6%) and (2) n=25 (2.6%). The cumulative infection rate for NMP (1.6%), doctors (3.8%) and nurses (9.7%) was connected to type and extent of COVID-19 patient contact. Despite COVID-19 positivity of 34.8% (46 of 132 beds), a risk-free management of hospital operation is possible to a certain extent if hygiene regulations and strict patient selection are followed. However, a COVID-19-free clinic cannot be expected due to silent carriers.