Evidence for multiple cases of recurrent Legionella infection: a Danish national surveillance study

Abstract

While case reports have documented recurrence of Legionnaires’ disease, the frequency of recurrent infections has not been systematically examined at a national level over multiple decades. Between 2000 and 2020 in Denmark, 21 individuals had repeat laboratory-identified Legionella infection, totalling 48 episodes of hospitalisation. The majority of these individuals had underlying comorbidities. In at least 3 of the 21 cases, a different Legionella serogroup was detected during the second episode of infection, which could indicate reinfection from a new source. These results emphasise that Legionella can, and does, reinfect high-risk individuals causing multiple hospitalisations.