According to the Institute for Occupational Health and Safety, Legionella was first identified in America at a Legion Convention in July 1976. There was an outbreak of approximately 182 cases, which resulted in 29 fatalities. The root cause for the outbreak was determined to emanate from the hotel’s cooling tower, which affected pedestrians as the walked past, inhaling the aerosol. Hence, the bacterium identified was given the name, Legionella. Thus, wherever conditions in a water system are ideal for the growth and transmission of the Legionella bacteria, there is a risk of infection. Therefore, unless Legionella is controlled in water systems, workers and even the public may be at risk.

What is Legionella?

Legionella is a pathogenic waterborne bacterium that results in infections called legionellosis—the most severe of which is Legionnaires’ disease.

Conditions leading to the growth of Legionella bacteria

The Legionella bacteria thrive well in conditions where:

  • Water temperatures are between 20oC and 45oC
  • Amoebae, a single cell organism which act as hosts for Legionella
  • Biofilm, a thin layers of microorganisms that form slime on surfaces in contact with water
  • A source of nutrients, such as sludge and corrosion

How does Legionella enter the body?

The Legionella bacteria enter the body when tiny droplets of water suspended in the air (aerosols) containing the bacteria or contaminated soil particles are inhaled. Legionella does not spread via person-to-person contact.

What are the symptoms of Legionellosis?

Legionellosis lack characteristic symptoms or signs. However, the severity of the disease arising from the Legionella bacteria can range from a mild form (Pontiac fever) to a more severe form (Legionnaires’ disease).

Pontiac fever is an influenza-like illness with a high infection rate and short incubation period, lasting last between 2 to 5 days.

Legionnaires’ disease in contrast, has an incubation period of 2 to 10 days but can last up to 20 days. Legionnaires’ disease is characterized by the onset of an acute and rapid pneumonia, as well as other non-specific symptoms, such as:

  • Muscle pains
  • Headaches
  • High fever usually 38C (100.4F) or above
  • Fatigue
  • Loss of strength
  • Changes in mental state, for example, confusion
  • A persistent cough that starts off dry but as the infection develops, phlegm becomes present
  • Chills
  • Shortness of breath
  • Chest pains

How is Legionnaires’ disease treated?

Legionnaires’ disease is treated using antibiotic therapy.

What populations are most at risk for contracting Legionella?

Although not everyone who is exposed to Legionella becomes infected, there are groups of people who are at a higher risk of infections. These people include:

  • Those over the age of 50
  • Smokers
  • Alcoholics
  • Men are more susceptible than women
  • Those suffering from chronic diseases, respiratory diseases, kidney diseases or have an impaired immune system

What occupations are at risk for Legionnaires’ disease?

While the majority of most workplaces are at risk of exposure to Legionella due to fact that they all have at least a hot and cold water system for the purposes of hygiene uses, as well as air conditioning, there are a few occupations at an increased risk. These include but are not limited to:

  • Water service providers
  • Maintenance workers who clean and maintain cooling towers
  • Air conditioning engineers
  • Plumbers dealing with contaminated showers or pipework
  • Spa pool cleaners
  • Workers in waste water in treatment plants
  • Construction workers involved in building demolition or refurbishment
  • Workers in leisure, hotel industry and cruise ships
  • Workers in industries with water spray systems, such as humidification in printing works and textile mills
  • Laboratory analysts handling Legionella contaminated samples

Measures to control the risk of exposure in the workplace

If the workplace has a water system, the following measures can be undertaken to control the risk of exposure to Legionella:

  • Identify the risk systems by checking to see if the system produces fine water droplets, if the water is stored or stagnant, and if the water temperature between 20oC and 45oC.
  • Follow the manufacturer's instructions for operation, cleaning, and maintenance.
  • Inspect and thoroughly clean cooling towers and evaporative condensers annually, replacing any corroded parts.
  • Do not build fresh air intakes close to cooling towers; this will allow contaminated aerosols to enter ventilation systems.
  • Examine, clean and test air filters for leaks, replacing them periodically.
  • Clean hot water tanks regularly, as they provide the optimum conditions for the growth of Legionella.
  • Regularly flush out the water system to prevent the water from stagnating.
  • Monitor the water system at risk for the growth of both aerobic bacteria and Legionella; aerobic bacteria will indicate the presence of biofilm.
  • Train and educate workers on working in environments where they are at risk of exposure to Legionella.
  • Encourage workers to use PPE when doing any maintenance work on water systems, even if Legionella has not been detected.

Who is responsible for controlling the risk in the workplace?

Employers have a duty to keep their workers safe. Therefore, it is the responsibility of the employer to control the risks associated with Legionella. Duties include:

  • Identifying and assessing sources of risk
  • Managing any risks
  • Preventing or controlling any risks
  • Keeping and maintain the correct records
  • Providing workers with the necessary PPE
  • Providing information to workers regarding what is Legionella, where it can be found in the workplace and precaution to take to reduce the risk of exposure

You catch it, when you breathe it

Legionella’s mortality rate lies between 10 to 12 percent. However, those that do survive Legionnaires’ disease are left very unwell due to the debilitating nature of the disease. Individuals are often left deaf or blind, with lost limbs, or suffering with brain damage. Unfortunately, because it is a respiratory disease, you do not catch it from drinking water; you catch it when you breathe in the bacteria.