Legionnaires' Disease From a Vacation Rental's Hot Tub: New York, 2024–2025

Summary

• Legionnaires' disease is caught by breathing in water droplets containing Legionella bacteria. Hot tubs make droplets and keep water at temperatures Legionella likes — and private short-term rentals aren't regulated like commercial properties.
• In 2024, New York health officials used whole genome sequencing to trace two cases to a vacation rental's hot tub, then used a public nuisance law to make sure it was properly cleaned before reopening.
• Rental owners need to know the risks of poorly managed hot tubs, and guests — especially those with health conditions — should take care.

The cases

In mid-October 2024, the New York State Department of Health learned of more Legionnaires' cases than usual in a western New York county, which had averaged 22 cases a year in 2022–2024: five patients in one city had positive urine antigen tests for L. pneumophila serogroup 1. Two were family members who had spent several nights at a short-term vacation rental 40 miles away, and had both used its hot tub, sauna and shower. Both fell ill in the first week of October with cough, fever and chills.

• Patient A, who had other health conditions, was hospitalized on antibiotics and a ventilator, and survived.
• Patient B went to an emergency department and was treated with antibiotics without admission.

No other cases were linked to the rental, and the other three patients had no common exposure.

Finding the source

Health staff took eight samples: five from sinks and showers — the house drew on a private well — plus two swabs of hot tub surfaces and one of hot tub water. The state's Wadsworth Center labs tested them by a quicker culture method (Legiolert, 7 days) and standard culture (10–14 days).

• L. pneumophila turned up in all three hot tub samples, and standard culture confirmed Legionella in the swab from the tub's air–water line (3,700 colony-forming units per mL).
• None was found in the household water — but those samples held so much chlorine that finding live bacteria was unlikely: the owner had bleached the well the night before the inspection.
• Patient A's sputum, negative at a commercial lab, grew L. pneumophila serogroup 1 at the state lab. Its genome differed from the hot tub isolates by only two to three single-letter changes — closely related, making the hot tub the likely source.

Why hot tubs: they're kept at about 100°F–104°F (38°C–40°C) — ideal for Legionella — and heat also breaks down disinfectants. This tub wasn't regularly disinfected.

A reluctant owner

• Officials told the owner to close the hot tub until it was professionally cleaned, a chemical treatment program was in place, and state-collected samples came back clean, and gave CDC guidance.
• About 4 weeks later, the tub was back in use: the owner had cleaned it personally, tested it with an unapproved method, and reopened without telling the state. Officials again explained the requirements.
• Four weeks after that, the listing still advertised the hot tub, and new guest reviews mentioned using it.
• The county then charged the owner under its sanitary code, declared the tub a public nuisance, and ordered it closed.
• After professional cleaning and two rounds of clean samples, the order was lifted on March 31, 2025; the professional now services it weekly.

What it means

Rental hot tubs are often linked to Legionnaires' disease. From 2014 to 2021, one in seven U.S. patients had stayed overnight in a hotel or vacation rental, and about half of those had used a hot tub. New York has matched patients to hot tubs before, including a private hot tub shared in 2021, and CDC has reported outbreaks tied to private-use hot tubs on cruise ships. New York regulates cooling towers, some health care facilities and public pools — but residential spas, including those at homes rented overnight, are exempt. The state has since posted guidance on hot tub risks and water treatment.

Recommendations

• Investigators should test any hot tub linked to cases that meet CDC's outbreak definition — visiting the site, sampling, using every tool including nuisance laws, and taking follow-up samples after cleanup.
• Rental owners should be told the risks of poorly managed hot tubs.
• Travelers should know rental hot tubs can pose a risk, especially with underlying health conditions. CDC has clinical guidance on Legionella infections.

Sources

Based on Matthew Morse, Martin Zartarian, Braden Savage and others (New York State Department of Health and county health staff), "Legionnaires Disease Associated with a Private-Use Hot Tub in a Vacation Rental Property — New York, October 2024–April 2025," MMWR, Centers for Disease Control and Prevention; published by CDC and in the public domain; rewritten in hubnx's own words.