Most people with Legionnaires’ disease get pneumonia, a serious lung infection. Most people recover from the illness.
Legionella bacteria are naturally found in environmental water sources, but at low levels that do not pose a health risk. However, they can grow and spread in man-made water systems like cooling towers, evaporative condensers, decorative fountains and hot water systems.
Water systems
Some countries, especially those in Europe, have enacted laws meant to control Legionella in buildings. They advocate that every building with a hot and cold water system have a plan for managing that system, monitoring certain parameters (not necessarily Legionella) to stay within limits, and validate that those controls are working by testing for Legionella at different points in the water system to detect changes in the bacteria.
The ASHRAE 188 standard and a document from the American Industrial Hygiene Association suggest that the approach to managing building water systems for Legionella should be based on the concepts of hazard assessment, risk identification, evaluation, and control. It also suggests that the approach should use a systems approach rather than a process or HACCP control method.
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Plumbing codes dictate nearly every facet of how building plumbing is designed and constructed, including materials used, allowable pipe size and length, water heater temperature, hot-water temperature from source to tap, the amount of time that hot water stays in distal pipes, and many more variables. These codes are largely enforceable prior to the signing of a certificate of occupancy.
Code requirements dictate almost all aspects of a water system during construction and renovation of a building, such as insulation, material selection for piping and fittings, and the number of fixtures per fixture, among other factors. These codes have little to do with controlling Legionella in existing buildings.
Research has shown that opportunistic pathogens like Legionella are more likely to grow in water pipes with “water age” problems, meaning that the pipe surfaces or internal components have been exposed to water at high temperatures and for long periods of time. This can lead to deposits that slow water flow, reducing temperature and increasing surface tension in the pipes, creating an environment that allows opportunistic pathogens to thrive.
State and local health departments typically work with building owners to investigate outbreaks of illness associated with Legionella, recommend remediation procedures for short-term control, and develop plans for addressing the root causes that led to the outbreaks. New York State’s regulations require hospitals and healthcare facilities to monitor their potable water systems for culturable L. pneumophila and institute a water management program if 30 percent of the samples contain the bacteria. They must also notify the state when a sample indicates a high Legionella count, and they are required to send the results to the New York State Department of Health.
Symptoms
Legionnaires’ disease causes pneumonia-like symptoms. The bacteria infect the lungs when you breathe in water droplets (aerosols) that contain Legionella. You can get infected by ingesting the bacteria, but that is less common. This is more likely to happen if you have a weakened immune system from certain medical conditions or medications (like chemotherapy, long-term use of corticosteroids, HIV infection, diabetes, or kidney or liver disease), or if you have a chronic illness that affects your respiratory system, such as chronic obstructive pulmonary disease or emphysema. You may also be more likely to get infected if you are over 50, male, or smoke.
The bacteria that cause Legionnaires’ disease can grow and spread in warm water. They can live in freshwater lakes and rivers, but usually people only become sick from them when they are exposed to man-made warm water systems, such as hot tubs or fountains, or the plumbing systems of large buildings, like hotels or nursing homes. The same bacteria can also cause Pontiac fever, a milder flu-like illness that doesn’t infect the lungs.
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Symptoms of legionellosis include fever, chills, a general feeling of illness, muscle aches, confusion, and diarrhea or vomiting. People with pneumonia from Legionella often have cough, difficulty breathing, and chest pain. They may also have a fever, headache, and confusion. In some cases, the bacterium can invade other parts of the body. This happens most often in people with a weak immune system because of certain illnesses or medications (like chemotherapy drugs, long-term use of corticosteroids, or organ transplantation). It can also happen when the bacterium invades tissues around surgical wounds.
Most people who have legionnaires’ disease recover with antibiotic treatment, but it can be a serious illness, especially for people who are older or have a weakened immune system. The illness can lead to complications, such as pneumonia, heart failure, or sepsis. If the disease is not treated quickly, it can be fatal. The symptoms of legionnaires’ disease start two to 14 days after you were exposed to the bacteria that cause it. If you have the illness, you may need to stay in hospital for a while.
Treatment
The bacteria that cause Legionnaires’ disease grow in warm water, such as that found in hot tubs and large plumbing systems or in cooling towers that are not properly maintained. They are not spread from one person to another through the air but are inhaled when water droplets (aerosols) containing the bacteria are released into the air. Inhaling these aerosols can cause pneumonia, a severe type of respiratory illness. People can also get a milder form of the illness, called Pontiac fever, which does not affect the lungs and is not contagious.
People who develop symptoms of Legionellosis should see a doctor, especially if they are hospitalized. The more quickly treatment is started, the less likely it is that serious complications will develop, such as respiratory failure or septic shock. Antibiotics are the mainstay of treatment. Levofloxacin or azithromycin are usually prescribed for 7-10 days.
Most cases of Legionnaires’ disease occur in health care facilities. This is probably because the patients are more susceptible to the infection and health care facilities often have suitable aquatic environments. Legionella infections may be sporadic or epidemic, community acquired or nosocomial (hospital-acquired).
Culturing of specimens from the lower respiratory tract is the preferred method of diagnosis because it is sensitive and specific. However, appropriate specimens are not always available, and culturing requires specially designed medium.
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Nucleic acid-based methods of detection are also becoming increasingly popular for the diagnosis of Legionella, but have a number of limitations, including their inability to detect bacteria that do not produce DNA, their lack of sensitivity with nonlower respiratory tract specimens, and their ability to generate false positive results in immunocompromised hosts. Direct immunofluorescence can detect antigens from Legionella but is not used very often.
Control of Legionella in health care facilities focuses on limiting the growth of the organism by disinfection and other means. For example, ensuring that only sterile water is used in filling and rinsing nebulizers and limiting use of recirculating water systems prevents Legionella growth. In addition, periodic superheating of water and regular chlorination of water limits bacterial colonization and growth.
Prevention
Preventing Legionella outbreaks starts with a risk assessment and setting appropriate control measures. Water safety specialists, such as Legionella Control International, can help with this process and ensure all necessary steps are taken to reduce the likelihood of an outbreak.
The bacteria live in natural water sources such as rivers, lakes and reservoirs, but can also be present in engineered plumbing systems like hot and cold water systems, cooling towers, whirlpool baths, fountains, humidifiers and garden watering equipment. The bacteria do not spread directly from one person to another and can only be transmitted by inhaling airborne water droplets containing legionella.
Cooling towers, water tanks and other plumbing equipment should be inspected regularly and disinfected as needed. The temperature of the water should be monitored and kept below 49degC to prevent Legionella growth. The pH of the water should be checked regularly to ensure it is within acceptable limits for disinfection. Regular cleaning and maintenance of mist-producing devices is important, especially shower heads, atomisers and whirlpool bathtubs. They should be cleaned and disinfected according to manufacturer instructions.
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Stagnant water is more likely to encourage the growth of Legionella compared to moving water. Stagnant water also decreases water temperature, reducing the effectiveness of disinfectants. A lack of water flow can also lead to the build-up of scale, sediment and gradual water organism accumulation on structural surfaces.
People who are at higher risk of Legionnaires’ disease include older people, smokers, those with a history of heavy drinking and people with chronic respiratory or kidney conditions. The infection can be fatal if not diagnosed and treated early.
It is a legal requirement for workplaces to have a designated responsible person who is experienced and knowledgeable in health and safety matters. This person, often a member of staff, should be appointed to put in place all required precautions against legionella, starting with the legionella risk assessment. This person can be chosen from within the business or an outside expert may be hired if preferred. It is a good idea to keep records of all legionella activities, as this provides evidence that the correct controls are in place.
