New York City’s 2026 Legionnaires’ disease outbreak has put cooling towers and rooftop mechanical systems back in the spotlight.
It has been a serious public-health event.
The outbreak began on Manhattan’s Upper East Side in early July. The NYC Health Department ultimately ordered 76 buildings to clean and disinfect cooling towers after positive initial PCR screening results. Subsequent laboratory testing confirmed live Legionella bacteria in 34 cooling towers at 33 buildings.
As of the City’s July 21 update, 82 people had been diagnosed and five had died. Health officials also reported that new cases had sharply declined and said they believed the source of exposure had been eliminated.
For building owners and property managers, the immediate lesson is obvious: cooling-tower maintenance, testing and compliance matter.
At Bell Bird Control, we think there is a second, narrower lesson worth considering:
When you’re inspecting critical rooftop equipment, look at the rest of the rooftop environment too.
What Is Legionnaires’ Disease?
Legionnaires’ disease is a serious type of pneumonia caused by Legionella bacteria.
People can become infected by breathing small droplets of water containing the bacteria. Cooling towers can become a source of community exposure because they contain recirculating water and release mist into the outside air.
Legionnaires’ disease is generally not transmitted from person to person.
New York City regulates the operation and maintenance of cooling towers, and those requirements became even stricter in 2026. Beginning May 8, operating cooling towers became subject to Legionella sampling at least every 31 days.
Those responsibilities belong to qualified water-management, laboratory, environmental and cooling-tower professionals.
Bird control is not Legionella control.
But that doesn’t mean bird activity around cooling towers and other rooftop equipment should be ignored.
Often, When You Get on the Roof, You Discover Something Else
Property managers know this phenomenon well.
You go onto a roof because of one problem and discover two others.
A cooling-tower inspection may also reveal deteriorated equipment, drainage problems, standing water, damaged materials—or substantial bird activity.
Pigeons and other pest birds commonly use commercial rooftops because buildings provide the things they need: food, water and protected places to roost or nest.
That can put birds around:
- Cooling towers
- HVAC equipment
- Outdoor air intakes and louvers
- Roof drains
- Parapets and ledges
- Mechanical screening
- Equipment platforms
- Service walkways
Sometimes the evidence is obvious.
There are birds everywhere.
Other times, the birds aren’t there when the engineer or inspector arrives—but the evidence they left behind is.
Droppings, Feathers and Nests Aren’t Just Unsightly
Bird problems are often treated initially as an appearance or cleaning problem.
They can be considerably more than that.
Bird droppings, feathers, nesting materials and food debris can accumulate around equipment and building surfaces. Nesting materials can obstruct drains. Droppings can damage certain building materials. Bird nests can harbor secondary pests, including bird mites.
And birds and their waste can carry bacteria and other microorganisms.
That is why significant accumulations of bird waste should be treated as a biological sanitation issue, not simply swept away as ordinary dirt.
Bell Bird Control has decades of experience inspecting commercial properties, professionally cleaning and disinfecting areas contaminated by bird waste, and developing humane exclusion and deterrent systems to help prevent recurring problems.
Are Birds Causing Legionnaires’ Disease?
This is where it is important to be precise.
Bell is not suggesting that birds caused the Upper East Side Legionnaires’ disease outbreak—or that finding birds near a cooling tower means they caused a positive Legionella result.
Determining the source of Legionella requires appropriate sampling, laboratory analysis and investigation by public-health and cooling-tower professionals.
The NYC Health Department’s investigation has focused on cooling towers and Legionella found within them. The City has not identified rooftop birds as the cause of this outbreak.
Our point is different.
If a building is already taking a careful look at its cooling tower and surrounding mechanical environment, why ignore a separate biological and sanitation problem sitting next to it?
A rooftop covered with bird droppings, feathers and nesting material deserves attention regardless of whether Legionella is present.
A Rooftop Inspection Should Look Beyond One Piece of Equipment
The current outbreak offers property managers an opportunity to think more broadly about preventive maintenance.
When someone is inspecting rooftop mechanical areas, look around.
Are pigeons roosting on the cooling-tower structure?
Are there nests around protected mechanical areas?
Are droppings accumulating on equipment or service walkways?
Are feathers and nesting materials collecting near drains?
Are birds congregating around outdoor air intakes or louvers?
Are employees and contractors walking through contaminated areas when servicing equipment?
Has an old bird deterrent system failed or become damaged?
Is somebody repeatedly paying to clean bird waste without correcting the reason birds keep returning?
Those are all legitimate building-management questions.
Don’t Just Clean It. Ask Why the Birds Are There.
Cleaning accumulated bird waste may be necessary, particularly when conditions are significant.
But cleanup alone doesn’t solve the underlying bird problem.
This is where the principles of Integrated Pest Management apply just as they do with rodents and insects.
Why are the birds choosing that location?
Where are they roosting?
Where are they nesting?
What is attracting them?
Can access to those locations be changed?
Would netting, bird wire, spikes, an appropriate electrical deterrent system or another humane exclusion technique make the location unsuitable?
The objective isn’t to harm birds.
It is to change the environment so they choose somewhere else.
The Best Building Professionals Look Beyond Their Individual Scope
There is a broader lesson here as well.
A cooling-tower specialist shouldn’t pretend to be a bird-control specialist.
A bird-control company shouldn’t pretend to be a Legionella consultant.
But good building professionals should recognize conditions outside their immediate scope and tell property management when they see them.
That’s why Bell has been discussing this issue with environmental consultants and other professionals who regularly inspect rooftops.
If someone performing a cooling-tower, Legionella or environmental inspection sees substantial bird activity or accumulated bird waste, flag it.
Then bring in the appropriate specialist.
Likewise, if Bell’s bird-control technicians encounter a condition involving mechanical equipment, water management or another issue outside our expertise, the appropriate response is to alert the building—not pretend it is a pest-control problem.
Good risk management requires good specialists who communicate with each other.
The Upper East Side Outbreak Is a Serious Reminder
The encouraging news is that NYC Health believes the source of exposure from the Upper East Side outbreak has been eliminated. All cooling towers with positive initial screening results underwent required remediation, and all towers subsequently confirmed to contain live Legionella had already been remediated.
But five deaths and dozens of illnesses are a powerful reminder that rooftop mechanical environments deserve serious attention.
Property managers should comply fully with NYC’s cooling-tower requirements and rely on qualified professionals for Legionella testing, water management, cleaning and disinfection.
And while you’re looking at the cooling tower, look around it.
If birds are roosting around critical mechanical equipment, droppings are accumulating, nesting material is collecting near drains or employees and contractors are working around contaminated areas, those conditions deserve attention too.
They may be a different problem.
But they’re still a problem.
Bell Bird Control has decades of experience helping commercial properties identify bird pressure, safely address bird-waste contamination and implement humane long-term bird-control systems.
Sometimes better risk management starts simply by noticing what else is happening on the roof.
Sources and Additional Information
NYC Department of Health and Mental Hygiene — Upper East Side Legionnaires’ Disease Investigation
https://www.nyc.gov/site/doh/health/health-topics/legionnaires-disease.page
NYC Department of Health and Mental Hygiene — Cooling Tower Registration and Maintenance
https://www.nyc.gov/site/doh/business/permits-and-licenses/cooling-towers.page
NYC Health — July 18, 2026 Update: Cooling Tower Remediation
https://www.nyc.gov/site/doh/about/press/pr2026/second-death-in-ues-legionnaires-disease-cluster.page
NYC Health — July 21, 2026: Confirmatory Legionella Testing Results
https://www.nyc.gov/site/doh/about/press/pr2026/preliminary-list-ues-cooling-towers-confirmed-live-legionella.page
Watch this space for more.
