According to the World Health Organization, Campylobacter spp. is one of four key global causes of bacterial diarrhoeal diseases around the globe. Luxembourg has one of the highest incidences in the EU, reaching an incidence rate of 159 per 100,000 inhabitants in 2014 with Campylobacter jejuni accounting for 90% of human cases.Between 2009 and 2013, a collaborative research consortium implicating different food safety administrations in Luxembourg conducted the research project HypoCamp, primarily focusing on environmental sources of Campylobacter infections (CORE C09/BM/09). In an epidemiological source attribution analysis using genetic data, we showed that most human cases could be attributed to poultry (61.2%), ruminants (33.3%), environmental water (4.9%) and swine (0.6%). Further modelling work showed that surface waters in Luxembourg were mainly contaminated by wild birds (61% of the water isolates). By modifying the existing housekeeping multilocus sequence typing (MLST) scheme to include molecular marker genes porA and gyrA, we discovered an unexpected endemic pattern in the temporal distribution of genotypes. Almost half of patients were infected by recurring genotypes of which a small subset clustered in time to form micro-epidemics (9% of isolates). We propose to investigate the phenomenon of recurring genotypes in more depth using state-of–the-art genomics. As a follow-up of our previous HypoCamp project, the current CampylOmic proposal aims to explore previously collected data of over 5000 partially sequenced isolates of C. jejuni from diverse sources. Surveillance by core genome multi-locus sequence typing (cgMLST) implemented in our laboratory since 2014 supports the presence of stable genotypes among clinical strains although more comprehensive and internationally validated schemes need to be developed to really confirm these initial findings.In the context of a One Health approach, we propose to conduct two novel pillars of research: (i) the carriage of generalist clonal complexes in wild birds, notably through the development of a culture-independent sequencing stategy, (ii) the specific phenotypic traits of endemic strains among humans, in particular their abilities to adhere to inert surfaces, their habituation ability to oxygen and their tolerance to oxidative stress. The idea is to complete the picture of the Campylobacter population structure in space and time and gain valuable insights on the environmental pathway that might explain the persistence over time of these genotypes.