Legionella longbeachaedetected in an industrial cooling tower linked to a legionellosis outbreak, New Zealand, 2015; possible waterborne transmission?

Abstract

SUMMARYA legionellosis outbreak at an industrial site was investigated to identify and control the source. Cases were identified from disease notifications, workplace illness records, and from clinicians. Cases were interviewed for symptoms and risk factors and tested for legionellosis. Implicated environmental sources were sampled and tested for legionella. We identified six cases with Legionnaires’ disease and seven with Pontiac fever; all had been exposed to aerosols from the cooling towers on the site. Nine cases had evidence of infection with eitherLegionella pneumophilaserogroup (sg) 1 orLegionella longbeachaesg1; these organisms were also isolated from the cooling towers. There was 100% DNA sequence homology between cooling tower and clinical isolates ofL. pneumophilasg1 using sequence-based typing analysis; no clinicalL. longbeachaeisolates were available to compare with environmental isolates. Routine monitoring of the towers prior to the outbreak failed to detect any legionella. Data from this outbreak indicate thatL. pneumophilasg1 transmission occurred from the cooling towers; in addition,L. longbeachaetransmission was suggested but remains unproven.L. longbeachaedetection in cooling towers has not been previously reported in association with legionellosis outbreaks. Waterborne transmission should not be discounted in investigations for the source ofL. longbeachaeinfection.