Legionella – yet another reminder of why management control is so important

At the time of writing, and according to NYC Health information 92 people have been reported as infected with Legionnaires’ disease, 7 people having sadly died.

NYC Health information also reported on the “remediation results” since the initial identification that there was problem, that:

• 183 cooling towers at 160 buildings have been tested for Legionella - of those:

• • 77 cooling towers at 75 buildings tested PCR positive for the presence of Legionella bacteria in initial testing.
  • 59 cooling towers at 58 buildings tested culture positive, confirming the presence of live Legionella bacteria. All have been cleaned and disinfected.
  • In total, 106 cooling towers have tested culture negative. All other results are pending at this time.

Legionnaires' Disease - NYC Health

To give some context to this, and as a result of a number of clusters/outbreaks in New York over the last decade, the NYC Department of Health and Mental Hygiene (DOHMH) enforces specific regulations for building owners and operators:

• Mandatory Registration: Every cooling tower must be registered through the online NYC Cooling Tower Registration Portal before seasonal startup.
• Monthly Legionella Sample Collection and Reporting

• From May 2026, Legionella sampling must be conducted monthly, with no more than 31 days between samples.
• A building's qualified person must report the date of each Legionella sample in the NYC Cooling Tower Registration Portal within five days of sample collection.
• The NYC Health Department may issue a summons to building owners that do not comply with this requirement.
  
  

• Summertime Hyperhalogenation
  • Hyperhalogenation must be performed in each cooling tower system between 1^st July 2026 and 31^st August each year and submit a declaration form to the NYC Cooling Tower Registration Portal within 30 days, that the work has been completed.
  • Cooling tower water must be tested for Legionella three to 31 days after completing the Hyperhalogenation.
  • The NYC Health Department may issue a summons to building owners that do not comply with this requirement.

• Outbreak Response: If elevated levels of bacteria are found, or during a public health emergency, owners are legally required to drain, deep clean, and chemically disinfect the entire system immediately.

For me looking at these findings, with 42% and 32% of a sampled 183 cooling towers testing positive for the presence of Legionella by PCR and culture respectively, there is concerns.

Testing for Legionella, while it does provide information, is a performance indicator rather than a control measure. It is also always best carried out with other testing and inspection work, rather than in isolation, as a better understanding of the systems water quality is produced and so what, if any, interventions are needed. I don’t know to what extent the national standard for Legionella, ANSI/ASHRAE Standard 188-2021 “Legionellosis: Risk Management for Building Water Systems”, is being adopted, but something isn’t working.

The mandated Summertime Hyperhalogenation is scheduled for between 1^st July and 31^st August each year, no doubt designed to coincide with the period of peak use and max load for evaporative cooling systems. The unusually warm weather during June could well have extended that period. With this Legionella outbreak/cluster starting in early/mid-July, and numbers of cooling tower systems testing positive, was the Hyperhalogenation work just too late as an intervention this year?

Finally, I also noted in the NYC Health report that:

 “Legionnaires' disease is not caused by any building's plumbing system. Residents in ZIP codes 10028, 10128, and 10075 can continue to drink tap water, bathe, shower, cook, and use your air conditioner at home.”

I fully understand the need to reassure the public, but the first sentence is just wrong, as indeed NYC should know having had recent outbreaks at:

• A senior living complex in Albany New York (Aug 2024)
• A public housing building in Brooklyn, New York (Jan 2023)
• A condominium complex in Bronx New York (Aug 2023)

Both New York City and New York State have mandatory testing regimes for specific systems and services, but bearing in mind that only last year another outbreak of Legionnaires’ disease caused 114 infections and 7 deaths in Central Harlem, is it enough (NYC have some of the strictest controls in place in the US too)?

The similarities with London in the late 1980s/early 1990s in terms of Legionella outbreaks is something I cannot shake. And perhaps, as with the introduction of L8 – first published in 1991 - in the UK, a more comprehensive management led approach to the problem is needed. I’m not saying L8 is perfect, but the current 4th iteration with over 240 pages of associated guidance is a very good basis for developing much more effective control.

Almost a year ago, I highlighted that cases of Legionnaires’ disease are increasing globally (Insight - Legionella causing problems around the World). For the USA, the CDC are reporting that rates of Legionnaires’ disease have “increased 9-fold” since 2000 (Legionellosis Surveillance and Trends | Legionella | CDC). We all need to recognise and respond to this risk by making sure our Legionella management is as good as it can be.