Legionellosis: Global Epidemiology and Current Perspectives on Diagnosis and Treatment

Abstract: The genus Legionella , first identified in 1977, comprises environmental Gram-negative intracellular bacteria that cause Legionellosis . Ubiquitous in freshwater and artificial water systems, Legionella species have an unclear global incidence, with reported cases likely significantly underestimated. Travel-associated Legionnaires’ disease (TALD) has increased recently and become a surveillance priority. For diagnosis, culture remains the gold standard but is time-consuming. Urinary antigen testing enables rapid screening, yet is mainly restricted to L. pneumophila serogroup 1. Molecular diagnostics, particularly PCR, offer high sensitivity and detect multiple serogroups, facilitating early diagnosis. Therapeutically, macrolides and fluoroquinolones constitute the mainstay of treatment, though evidence supporting combination therapy remains limited. Increasing reports of antimicrobial resistance underscore the need for strengthened antibiotic stewardship and global surveillance. Future efforts should prioritize large-scale epidemiological studies, diagnostic standardization, treatment optimization, and resistance monitoring to reduce disease burden. Keywords: Legionella , Legionellosis , epidemiology, resistance, treatment