COVID-19 in healthcare workers in three hospitals in the South of the Netherlands, March 2020

Sikkema, R. S.; Pas, S.; Nieuwenhuijse, D. F.; O'Toole, A.; Verweij, J.; van der Linden, A.; Chestakova, I.; Schapendonk, C.; Pronk, M. R.; Lexmond, P.; Bestebroer, T.; Overmars, R. J.; van Nieuwkoop, S.; van den Bijllaardt, W.; Bentvelsen, R. G.; van Rijen, M. M. L.; Buiting, A. G. M.; van Oudheusden, A. J. G.; Diederen, B. M.; Bergmans, A. M. C.; van der Eijk, A.; Molenkamp, R.; Rambaut, A.; Timen, A.; Kluytmans, J. A. J. W.; Oude Munnink, B. B.; Kluytmans, M.; Koopmans, M. P. G.

Background: Ten days after the first reported case of SARS-CoV-2 infection in the Netherlands, 3.9% of healthcare workers (HCWs) in nine hospitals located in the South of the Netherlands tested positive for SARS-CoV-2 RNA. The extent of nosocomial transmission that contributed to the HCW infections was unknown. Methods: We combined epidemiological data, collected by means of structured interviews of HCWs, with whole genome sequencing (WGS) of SARS-CoV-2 in clinical samples from HCWs and patients in three of nine hospitals that participated in the HCW screening, to perform an in-depth analysis of sources and modes of transmission of SARS -CoV-2 in HCWs and patients. Results: A total of 1,796 out of 12,022 HCWs (15%) of the three participating hospitals were screened, based on clinical symptoms, of whom 96 (5%) tested positive for SARS-CoV-2. We obtained complete genome sequences of 50 HCWs and 18 patients. Most sequences grouped in 3 clusters, with 2 clusters displaying local circulation within the region. The observed patterns are most consistent with multiple introductions into the hospitals through community acquired infections, and local amplification in the community. Conclusions: Although direct transmission in the hospitals cannot be ruled out, the data does not support widespread nosocomial transmission as source of infection in patients or healthcare workers.