An outbreak of SARS-CoV-2 Alpha variant (Pango lineage B.1.1.7) was detected at a primary school (School X) in Lansingerland, the Netherlands, in December 2020. The outbreak was studied retrospectively, and population-based screening was used to assess the extent of virus circulation and decelerate transmission. Cases were SARS-CoV-2 laboratory confirmed and were residents of Lansingerland (November 16th 2020 until February 22th 2021), or had an epidemiological link with School X or neighbouring schools. The SARS-CoV-2 variant was determined using variant PCR or whole genome sequencing. A questionnaire primarily assessed clinical symptoms. A total of 77 Alpha variant cases were found with an epidemiological link to School X, 16 Alpha variant cases linked to the neighbouring schools, and 146 Alpha variant cases among residents of Lansingerland without a link to the schools. The mean number of self-reported symptoms was not significantly different among Alpha variant infected individuals compared to non-Alpha infected individuals. The secondary attack rate (SAR) among Alpha variant exposed individuals in households was 52% higher compared to non-Alpha variant exposed individuals (p = 0.010), with the mean household age, and mean number of children and adults per household as confounders. Sequence analysis of 60 Alpha variant sequences obtained from cases confirmed virus transmission between School X and neighbouring schools, and showed that multiple introductions of the Alpha variant had already taken place in Lansingerland at the time of the study. The alpha variant caused a large outbreak at both locations of School X, and subsequently spread to neighbouring schools, and households. 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.

Background: There is a worldwide shortage of medical-grade face masks. Donning masks can play an important role in curbing the spread of SARS-CoV-2. Aim: To conclude whether there is an effective mask for the population to wear in public that could easily be made during a medical face mask shortage using readily available materials. Methods: We determined the effectiveness of readily available materials and models for making a face mask. The outcomes were compared with N95/FFP2/KN95 masks that entered the Netherlands in April–May 2020. Masks were tested to determine whether they filtered a minimum of 35% of 0.3-μm particles, are hydrophobic, seal on the face, are breathable, and can be washed. Findings: Fourteen of the 25 (combinations of) materials filtered at least 35% of 0.3-μm particles. Four of the materials proved hydrophobic, all commercially manufactured filters. Two models sealed the face. Twenty-two of the 25 materials were breathable at <0.7 mbar. None of the hydrophobic materials stayed intact after washing. Conclusions: It would be possible to reduce the reproduction rate of SARS-CoV-2 from 2.4 to below one if 39% of the population would wear a mask made from ePM₁ 85% commercially manufactured filter fabric and in a duckbill form. This mask performs better than 80% of the imported N95/FFP2/KN95 masks and provides a better fit than a surgical mask. Two layers of quilt fabric with a household paper towel as filter is also a viable choice for protecting the user and the environment.