COVID-19: SARS-CoV-2 susceptibility in healthcare workers – cluster study at a German Teaching Hospital

Purpose: The local health department (in German: Gesundheitsamt) ordered a shutdown of a teaching hospital due to the severe acute respiratory syndrome coronavirus (SARS-CoV-2) outbreak – one index patient and five infected healthcare workers – and put it under quarantine. For the first time, all patients plus all employees of one German hospital (healthcare providers, physicians, and nurses) were tested to detect silent or asymptomatic carriers. Methods: A serial polymerase chain reaction (PCR) test for SARS-CoV-2 was performed three times (1) between April 3rd and 5th, 2020 [n = 1171], (2) between April 8th and 9th, 2020 [n = 953] and (3) between April 14th and 17th, 2020 [n = 983]. Results: The teaching hospital’s proven coronavirus disease 2019 (COVID-19) patient load on Friday, April 3rd, 2020, was 34 patients, of whom 11 were on ventilation in the intensive care unit (ICU), one in the intermediate care unit (IMC), and 22 in the infectious disease ward. Another 32 patients in a different infectious disease ward were suspected for COVID-19 with test results pending. COVID-19 silent carrier (asymptomatic) positivity rates based on the phases of testing were (1) n = 24 (2.1%), (2) n = 25 (2.6%) and n = 9 (0.9%). The cumulative infection rate for healthcare providers, physical therapists, physicians, and nurses was 1.8%, 4.5%, 4.8%, and 11.9% which were associated with the type and extent of COVID-19 patient contact (p < 0.05). Conclusion: Despite prior proper preparation, a COVID-19 positive patient load of up to 34.8% (46 of 132 hospital beds) resulted in a 10- to 20-fold increase in risk for healthcare workers for SARS-CoV-2 compared to the general population. Because of asymptomatic carriers, a COVID-19-free hospital cannot be expected to exist. Based on our experience, repeated testing of all staff members with patient contact is necessary and is the best option to effectively contain the virus. Those having the most contact with patients had the highest risk of becoming infected (10- to 20-fold higher risk), with nurses being at the highest risk.