Three Legionnaires' Cases at a Resort With a Spa and Fountain
An 86-room resort hotel receives a call from the local health department: three laboratory-confirmed Legionnaires' disease cases (two urinary antigen positive, one culture confirmed) had onset on June 3, June 19, and July 1, and all three guests stayed in the east wing during the 14 days before onset. The hotel has an indoor whirlpool spa, a lobby decorative fountain, and two evaporative cooling towers. The spa free-chlorine log shows several days below the code minimum, and the fountain is drained and refilled monthly. The general manager asks whether this is person-to-person spread, whether the spa must close, and who must be notified. Records show 60 of the 142 east-wing guests used the spa; none of the other 82 reported illness.
1. Assess the likely transmission route. Compare exposure-specific attack rates and state what evidence would confirm or refute a common-source aerosol.
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Reasoning steps
- Route: Legionella is acquired by inhaling contaminated aerosol (or aspirating contaminated water), not by person-to-person spread. The 2-14 day incubation fits the stated exposure window.
- Attack rates: spa users 3/60 = 5.0%; non-users 0/82 = 0%. All three cases share a wing and span a month, which argues for a persistent point source rather than a single bad batch of water.
- Candidate sources: spa (aerosol-generating, chlorine lapses), fountain (aerosol, monthly drain is not a control), and cooling-tower plume if the east wing is downwind.
- Caveats: the 5% figure assumes complete case ascertainment and accurate spa-use histories; mild cases may be missed. A single culture-matched environmental isolate would strengthen the link far more than another urinary antigen result.
Conclusion: common-source aerosol is the leading hypothesis; ask all three cases about spa, fountain, and window/outdoor exposure, and check wind direction relative to the towers before narrowing the source.
2. The GM wants to keep the spa open and handle notification internally. What are the facility's reporting and closure obligations, and who actually holds closure authority?
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Reporting
- Legionellosis is reportable in most US jurisdictions; the health department already has the cases, so the hotel's duty is full cooperation and prompt disclosure of water-system information, not first notification.
- Separate legal duties may apply: cooling-tower registration and post-case notification ordinances in many cities; pool/spa code requirements; OSHA duties to employees; and any local ordinance requiring an environmental assessment after a cluster.
Closure authority
The GM does not decide this alone. Under most pool/spa codes the regulator can order immediate closure when disinfectant is below the required minimum, and reopening requires corrective action and often inspector approval. Voluntary closure pending direction is the defensible choice when chlorine has repeatedly been below minimum.
Judgment point: internal handling is not an option once the regulator is involved. Document decisions, times, and who authorized them, and preserve the spa and fountain logs rather than reconstructing them later.
3. List immediate actions for the first 72 hours, including sampling, and explain why drain-and-refill is not adequate remediation.
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First 72 hours
- Close the spa voluntarily if chlorine is below code minimum; do not reopen until treated and approved.
- Sample before treatment: about 1 L from spa water, filter housing, and inlet; fountain water and fittings; both cooling towers (basin and drift area). Request culture with serogroup and sequence-based typing so results can be compared with the clinical isolate.
- Decontaminate: hyperchlorinate the spa and its piping per code, clean or replace filters and media, and mechanically clean the fountain and its recirculation line. Treat or shut down towers if results or plume analysis support it.
- Notify exposed guests with a symptom advisory and a number to call; state clearly that there is no person-to-person risk.
- Log every action with time, responsible person, and verification result.
Why not drain and refill: biofilm in piping, jets, and fittings is the reservoir. Replacing the water leaves the biofilm and the aerosol-generating fittings intact, and the system can be recolonized within days, giving false reassurance before culture results return.