One year of laboratory-based COVID-19 surveillance system in Belgium: main indicators and performance of the laboratories (March 2020-21)

Abstract

Background: With the spread of coronavirus disease 2019 (COVID-19), an existing national laboratory-based surveillance system was adapted to daily monitor the epidemiological situation of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in the Belgium by following the number of confirmed SARS-CoV-2 infections, the number of performed tests and the positivity ratio. We present these main indicators of the surveillance over a one-year period as well as the impact of the performance of the laboratories, regarding speed of processing the samples and reporting results, for surveillance.

Methods: We describe the evolution of test capacity, testing strategy and the data collection methods during the first year of the epidemic in Belgium.

Results: Between the 1^st of March 2020 and the 28^th of February 2021, 9,487,470 tests and 773,078 COVID-19 laboratory confirmed cases were reported. Two epidemic waves occurred, with a peak in April and October 2020. The capacity and performance of the laboratories improved continuously during 2020 resulting in a high level performance. Since the end of November 2020 90 to 95% of the test results are reported at the latest the day after sampling was performed.

Conclusions: Thanks to the effort of all laboratories a performant exhaustive national laboratory-based surveillance system to monitor the epidemiological situation of SARS-CoV-2 was set up in Belgium in 2020. On top of expanding the number of laboratories performing diagnostics and significantly increasing the test capacity in Belgium, turnaround times between sampling and testing as well as reporting were optimized over the first year of this pandemic.

Keywords: Belgium; COVID-19; Laboratory-based surveillance; SARS-CoV-2.

Fig. 1

Overview of the laboratory-based COVID-19 surveillance outline and major social distancing measures (“lockdowns”) that were implemented, February 2020 – February 2021, Belgium

Fig. 2

Number of COVID-19 diagnostic tests reported per day and the moving average over seven centered days (dark green line) per date of test result, from the 1^st of March 2020 until the 28^th of February 2021, Belgium. Bars are colored regarding the implemented testing strategy and the legend is numbered in correspondence to the numbered testing strategies in Table 1

Fig. 3

Daily number of COVID-19 laboratory confirmed cases (light green bars), the moving average over seven days (dark green line) and positivity ratio (orange line), from the 1^st of March 2020 until the 28^th of February 2021, Belgium

Fig. 4

Weekly proportion of COVID-19 tests by delay between date of sampling and date of test result, from the 1^st of March 2020 (week 10) until the 28^th of February 2021 (week 08), Belgium

Fig. 5

Weekly proportion of COVID-19 tests by delay between date of test result and date of reporting, from the 5^th of May 2020 (week 19) until the 28^th of February 2021 (week 08), Belgium

Fig. 6

Weekly proportion of COVID-19 tests by delay between date of sampling and date of reporting, from the 5^th of May 2020 (week 19) until the 28^th of February 2021 (week 08), Belgium