Alternative routes for dissemination of Legionella pneumophila causing three outbreaks in Norway.

Three outbreaks of Legionnaires' disease were reported in the Fredrikstad/Sarpsborg community, Norway, in 2005 and 2008 caused by the L. pneumophila ST15 and ST462 strains determined by sequence based typing. In this retrospective study, we suggest that the aeration ponds, a part of the biological treatment plant at Borregaard Ind.