Western blot serology is useful to distinguish between carriers and patients; paradoxical responses of the antibodies were investigated.

In cases of chronic rhinitis, ozena and rhinoscleroma should be kept in mind, even in developed countries, and systematically screened for, especially as there are specific diagnostic tools and effective treatments available.

Cross-reactivity between C. burnetii and Legionella spp. has long been known and should be considered in patients with persistent infections. It is important to establish the definite diagnosis because the antibiotic treatment regimens and duration are significantly different. To the best of our knowledge, we reported here the first case of mediastinitis associated to C. burnetii and we diagnosed this persistent infection despite low anti-C. burnetii phase I IgG levels.