Population-based screening in a Dutch municipality after a primary school outbreak of the SARS-CoV-2 Alpha variant

9 November 2022

The respiratory illness COVID-19 is caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which emerged in Wuhan, China, late 2019. SARS-CoV-2 rapidly spread globally and caused a major public health and economic impact.

The SARS-CoV-2 Alpha variant was first detected in November 2020, in samples collected in September from cases in the United Kingdom (UK). This variant became the predominant strain in the UK in December 2020, only weeks after it had first been identified. Initial epidemiological studies suggested an overrepresentation of Alpha variant cases among the age group 0–19 years, and a higher reproduction number for this variant compared to pre-existing variants.

Following the public health alert from the UK, increased surveillance was done in the Netherlands, including testing of travellers from the UK and sequencing of a random sample of positives. This resulted in the first detection of an Alpha variant infection in the Netherlands in December 2020, and contact tracing showed a link with the first Dutch Alpha variant case and an outbreak at a primary school (School X) in the municipality Lansingerland. 

In October 2022, a RECOVER paper was published that studied the outbreak retrospectively and prospectively, from December 2020 until February 2021. The aim was to get a better understanding of the disease severity and transmission of the Alpha variant

Alpha and non-Alpha variant cases were cases confirmed by additional laboratory testing (variant PCR or whole genome sequencing). Symptomatic or post-exposure testing (routine testing) and population-based screening were performed in four phases based on the course of the outbreak. This assessed the extent of virus circulation and decelerated transmission. 

The alpha variant caused a large outbreak at School X, and subsequently spread to neighbouring schools, and households. The results showed that population-based screening (together with other public health measures) nearly stopped transmission of the outbreak strain, but did not prevent variant replacement in the Lansingerland municipality.

Read the paper here

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