Background: The Dutch province of Limburg borders the German district of Heinsberg, which had a large cluster of COVID-19 cases linked to local carnival activities before any cases were reported in the Netherlands. However, Heinsberg was not included as an area reporting local or community transmission per the national case definition at the time. In early March, two residents from a long-term care facility (LTCF) in Sittard, a Dutch town located in close vicinity to the district of Heinsberg, tested positive for COVID-19. In this study we aimed to determine whether cross-border introduction of the virus took place by analysing the LTCF outbreak in Sittard, both epidemiologically and microbiologically. Methods: Surveys and semi-structured oral interviews were conducted with all present LTCF residents by health care workers during regular points of care for information on new or unusual signs and symptoms of disease. Both throat and nasopharyngeal swabs were taken from residents suspect of COVID-19, based on regional criteria, for the detection of SARS-CoV-2 by Real-time Polymerase Chain Reaction. Additionally, whole genome sequencing was performed using a SARS-CoV-2 specific amplicon-based Nanopore sequencing approach. Moreover, twelve random residents were sampled for possible asymptomatic infections. Results: Out of 99 residents, 46 got tested for COVID-19. Out of the 46 tested residents, nineteen (41%) tested positive for COVID-19, including 3 asymptomatic residents. CT-values for asymptomatic residents seemed higher compared to symptomatic residents. Eleven samples were sequenced, along with three random samples from COVID-19 patients hospitalized in the regional hospital at the time of the LTCF outbreak. All samples were linked to COVID-19 cases from the cross-border region of Heinsberg, Germany. Conclusions: Sequencing combined with epidemiological data was able to virtually prove cross-border transmission at the start of the Dutch COVID-19 epidemic. Our results highlight the need for cross-border collaboration and adjustment of national policy to emerging region-specific needs along borders in order to establish coordinated implementation of infection control measures to limit the spread of COVID-19.
|Journal||BMC Infectious Diseases|
|Publication status||Published - 4 May 2021|
Bibliographical noteFunding Information:
This study has been financially supported by the Dutch organization for health research and healthcare innovation (ZonMw 10430022010001). ZonMw had no role in the design of the study and collection, analysis, and interpretation of data and in writing the manuscript.
The authors would like to thank all healthcare personnel of the participating LTCF and the Public Health Service South-Limburg for the data collection, along with all laboratory personnel involved in the sequencing of the strains. We are also grateful for the sequences from GISAID?s EpiFlu Database. Unfortunately, we could not incorporate a table in the methods section due to the huge number of people who have contributed, but we would like to thank all the authors, originating and submitting laboratories for sharing these SARS-CoV-2 sequences. We would also like to thank Kevin Konings from the South Limburg Public Health Service for his assistance in visualising the maps used in Fig. 3 of the manuscript.
© 2021, The Author(s).