Legionellosis in the occupational setting

Legionellosis is the common name for two infections, Legionnaires' disease (LD) and Pontiac fever (PF), both caused by Legionella bacteria. Although with low incidence, LD is an important cause of community- and hospital-acquired pneumonia. Among community-acquired cases, an increasing number was reported to be linked to the occupational setting, posing the need for better recognition of work activities at risk of legionellosis. In this work, we selected and reviewed relevant literature on cases of occupational legionellosis published between 1978 and 2016 in order to define the: 1) etiology; sources of infection, work activities at risk, iv) infection rates, v) predisposing factors, vi) mortality and vii) country distribution. To our knowledge, this is the first review to provide an analysis of cases of occupational legionellosis. A literature search in the PubMed website was started on January 31, 2015 and ended on June 30, 2016. Cases of occupational legionellosis documented in the scientific literature were retrieved from PubMed upon interrogation with the following keywords: Legionella pneumophila, Legionnaires' disease, Pontiac fever, and legionellosis, in combination with employees, workers, and occupational. Abstracts were reviewed, and applicable articles were obtained. Only articles that met the inclusion criteria were considered. Forty-seven articles were selected, reporting confirmed cases of legionellosis which occurred over 66 years (1949-2015), and involved 805 workers (221, LD; 584, PF). Fatalities were all associated with LD, resulting in 4.1% mortality. The most common etiologic agents were Legionella pneumophila (58.5%) and Legionella feeleii (39.4%), the latter being responsible for only one large outbreak of PF. Workplaces more frequently associated with occupational legionellosis were industrial settings (62.0%), office buildings (27.3%) and healthcare facilities (6.3%), though cases were also reported from a variety of workplaces, e.g. artesian excavation and horticultural sites, lorry parks, ships, water and sewage plants. With few exceptions, cases occurred in industrialized countries of the northern hemisphere. Overall, our review highlights an extended spectrum of occupational categories at risk for legionellosis. For all categories, infection originated from exposure to work-generated aerosols contaminated with Legionella spp., and industrial facilities equipped with cooling towers or coolant systems were the most common occupational settings. These observations should raise awareness of the risk of acquiring legionellosis at work, and help to improve prevention and control measures for this infrequent but still problematic disease.