New approach to environmental investigation of an explosive legionnaires´ disease outbreak in Spain: early identification of potential risk sources by rapid Legionella spp immunosensing technique

BACKGROUND: An explosive outbreak of Legionnaires’ disease (LD) was identified on 11 December 2015 in Manzanares, Ciudad Real, Spain, and was declared closed by 03 February 2016. The number of declared cases was 593 with 277 confirmed cases so that it can be considered as one of the outbreaks with highest attack rate. This rate could be attributed to the ageing of the population, among others, in addition to various risk factors and habits, and the meteorological conditions (thermal inversion) maintained in this municipality at the time. The Public Health Services succeeded in breaking the bacterial transmission. Several facilities were early identified by microbiological analysis, including a cooling tower and a decorative fountain, as possible infectious sources. Rapid analytical techniques for rapid Legionella detection and the shutdown and preventative closure of positive installations have been considered key elements in the control of this outbreak. RESULTS: Rapid microbiological analysis helped to the early identification of potential risk sources in a Legionnaires´ disease outbreak, reducing decision-making processes according to the actual needs of the intervention in public health and shortening the exposure of the population. CONCLUSIONS: Protocolized and immediate intervention in an outbreak is a crucial issue to reduce their effects on public health. For this, identification and control of the suspicious sources able to disseminate the bacteria and cause the illness is required. Rapid analytical techniques like immunomagnetic separation (IMS) method based on the whole bacterial cell detection are shown as excellent tools to investigate all the potential sources of risk.