Legionella pneumophila sg 1 outbreak connected to city water network, Finland 2021

We report a Legionella pneumophila sg1 outbreak in Kuopio, Finland with 12 Legionnaires' disease cases between Jan 2020 - May 2021. Sources of infection were identified to be 9 residential building waters systems (9 cases, 1 in each apartment building) and one hospital water system (3 cases). Water isolates (shower) and patient isolates matched with a maximum of 2/1443 allele cgMLST difference. We have uploaded 5 sequences representing all different sequence profiles of the outbreak strain originating from 4 homes and a hospital.