Legionnaires' disease is a form of pneumonia, and the disease gets its name from the Legionella bacteria that causes it. These bacteria are typically found in natural bodies of water such as rivers and lakes. However, they become dangerous when they grow in artificial installations that use water.
The symptoms of Legionnaires' disease are similar to those of a flu infection (influenza): fever, chills, muscle aches and cough. The range of symptoms can also include headache, fatigue, loss of appetite, confusion and diarrhea. Compared to COVID-19, pneumonia caused by Legionnaires' disease is much more dangerous, with a fatality rate of 10%.
Improve your building's water quality and protect its occupants against disease.
How do Legionella bacteria grow and spread?
Legionella bacteria thrive in warm water at temperatures between 68°F and 122°F, especially if the water is stagnant or slow-moving. According to the U.S. Department of Health and Human Services, Legionella bacteria often grow in the following components of building water systems:
- Storage tanks and expansion tanks
- Water heaters
- Water hammer arrestors
- Water Filters
- Taps, manual and electronic
- Aerators and flow restrictors
- Showers and hoses
- Pipes, valves and connections
- Atomizers, air washers and humidifiers
- Ice machines
- Hot tubs
- Sources
- Cooling towers
- Medical devices
- In general, equipment that is not used frequently
Legionnaires' disease is acquired by inhaling water droplets contaminated with Legionella. The disease cannot be acquired by drinking contaminated water, unless it accidentally reaches the lungs while drinking. Furthermore, the disease cannot spread between humans – being close to an infected person does not pose a risk.
Even when Legionnaires' disease cannot be transmitted between people, building owners should act quickly if a case is reported on their property. The presence of Legionella bacteria is a clear warning sign that the water systems in a building need attention.
Individuals who meet any of the following conditions are at greater risk of contracting Legionnaires' disease:
- Age 50 or older
- Smokers
- Patients with chronic lung disease
- People with weakened immune systems
- People taking medications that weaken the immune system
How common is Legionnaires' disease in New York?
The latest report on Legionnaires' disease from the New York City Department of Health and Mental Hygiene is from 2017. There were 435 cases reported that year, and there are typically between 200 and 500 cases annually. The number of cases may seem small in a city with a population of more than 8.6 million, but the rate of Legionnaires' disease cases has increased by 8.1% annually between 2010 and 2017.
- The 2015 Legionnaires' disease outbreaks were the most serious in recent years. They affected 133 people, mainly in the Bronx, and there were 16 victims. Many of the cases in 2015 were caused by poorly maintained cooling towers.
- More recently, in 2018, an outbreak in Washington Heights infected 27 people and claimed one casualty.
- In July 2019, two simultaneous cases of Legionnaires' disease occurred at Manhattan Plaza.
Legionnaires' disease can be treated effectively with antibiotics, especially if the patient receives prompt attention. However, the disease can have serious complications if left untreated: the fatality rate is around 10% and patients with pre-existing health problems are at greater risk. Hospital-acquired infections are even more dangerous, with a 25% mortality rate.
What do codes and standards say about Legionella?
Given the importance of keeping Legionella under control in building water systems, ASHRAE created Standard 188, called Legionellosis: Risk Management for Building Water Systems. The first version was published in 2015 and an updated version was published in 2018.
ASHRAE Standard 188 specifies the types of buildings and system components that require a water management program, as well as the minimum requirements for such a program. ASHRAE standards alone are not mandatory, but they provide a fundamental reference for building codes at the state and local level.
In New York City, Local Law 77 of 2015 requires all cooling towers to be registered with the Department of Buildings. Every year, cooling tower owners must certify that the units have been inspected, tested, cleaned and disinfected. Cooling towers must also be registered with the NYS Department of Health.
The New York Administrative Code provides detailed requirements for cooling towers based on the ASHRAE 188 standard, covering the following aspects:
- Maintenance program and records
- Process control measures
- Automated water treatment
- System shutdown and startup
- Commissioning of new cooling towers
Currently, New York codes only address Legionella in cooling towers. However, several design measures can be implemented to control these bacteria in other water systems:
- Storing hot water at 140°F is one of the most effective ways to deal with Legionella, as that temperature is too hot for the bacteria. 140°F is also a dangerous water temperature for humans, but this is resolved by mixing cold water before it reaches the plumbing.
- Ultraviolet disinfection systems can also kill Legionella. UV radiation is most effective when the water content of sediment and scale is first reduced. This can be achieved with filtration and anti-scale systems.
- Dead legs in plumbing systems should be avoided at all costs. They are commonly found in plumbing installations that have been modified, leaving pipes that go nowhere. Legionella can easily grow in stagnant water trapped in dead legs.
- When tankless water heaters are used, recirculation systems can help prevent Legionella. Furthermore, they reduce the time needed for hot water to reach the installations, saving water.
Responding to Legionnaires' Disease Cases
If a building occupant is infected with Legionella, the owner is legally required to report the case to the New York Department of Health and Mental Hygiene. The same applies if Legionella bacteria are detected in a building system, even if no one has been infected yet.
The Department will then visit the affected building to conduct a detailed investigation. They will work with building staff to develop a Legionella sampling plan in order to test all of the facility's water systems.
A Legionella remediation plan is developed based on the test results, and the building owner must implement the plan within the time frame specified by the department. This includes a short-term remediation plan, which must be implemented within 96 hours.
Conclusion
To prevent the growth of Legionella and protect building occupants, the best solution is to have well-designed plumbing and plumbing fixtures. The design should avoid areas where hot water can accumulate, as this creates an ideal environment for Legionella.
If you are planning a major renovation, consider a professional evaluation of your plumbing installation. This way, it is possible to identify potential measures to conserve water, which also saves energy in pumping and heating. Parts of the facility that are susceptible to Legionella growth can be identified and corrected.