Déjà Vu All Over Again: Two Legionella Outbreaks, One Hotel, Pennsylvania, 2012

BACKGROUND:  Legionellosis results from inhalation of Legionella spp.-contaminated aerosols and clinically manifests as Legionnaires’ disease (LD) or the milder Pontiac Fever (PF). Outbreaks that include both LD and PF are infrequent. Outbreaks are often travel associated.  During 2012, we investigated sequential outbreaks of legionellosis linked to the same Pennsylvania hotel; the second included LD and PF cases.  

METHODS:  Case finding included review of Pennsylvania’s surveillance database for Legionella cases linked to the hotel and active surveillance of hotel registrants and staff. All cases had symptom onset ≤14 days after hotel stay. Confirmed LD cases had positive Legionella urine antigen tests. Probable LD cases had pneumonia and fever or cough. Probable PF cases had fever and one or more of the following: myalgia, cough, headache, diarrhea. Environmental samples were tested for Legionella.

RESULTS:  The hotel had 96 guest rooms and a common indoor pool and whirlpool spa; some rooms also had in-room whirlpool tubs.  Hotel water was from an independent, non-disinfected well water system.  A total of 3,620 hotel registrants from 47 states, Canada, and Australia were contacted during the January (Outbreak 1) and June-August 2012 (Outbreak 2) events.  Outbreak 1 consisted of two confirmed LD cases who stayed at the hotel in January 2012; both used the hotel spa which had a non-detectable chlorine level and 8 of 9 spa water or swab samples were PCR positive for Legionella. All post-remediation samples from the spa were negative. Outbreak 2 consisted of 7 confirmed LD, 9 probable LD and 18 probable PF cases who stayed overnight at the hotel during June-August 2012, but only 15% used the spa. Thirteen of 29 environmental samples were Legionella-positive by PCR or culture. Positive samples were from the hotel spa, hot and cold potable water, in-room whirlpool tubs and showerheads.  Spa and potable water systems underwent emergency remediation; weekly post-remediation samples were Legionella-negative.

CONCLUSIONS: The sequential outbreaks of legionellosis suggest an ongoing source of contamination of the water supply at the hotel.  The initial outbreak was terminated by remediation of the spa; additional cases did not occur for 5 months.  This outbreak highlights how travel associated outbreaks can involve large numbers of potentially exposed persons.  It also highlights the need to address and remediate all potential sources of Legionella when an outbreak is recognized.  Institutional potable water systems should be closely monitored for proper disinfection to suppress growth of microbes like Legionella.