Legionnaire’s Disease remains a continual public threat of today’s modern world. The first outbreak was identified in Philadelphia USA in 1976 at a convention of the American Legion. It affected 221 and 34 died during the out break. This sparked mass panic in the media and public in the US. Since then massive outbreaks were spotted world wide. The biggest outbreak that claimed lives was in Murcia, Spain.

Legionellosis is an infection caused by the bacterium Legionella pneumophila. The disease had two distinct forms.

Legionnnaires disease, the more severe form of infection which includes pneumonia and Pontiac fever a milder illness. Legionnaires disease, due to Legionella sero group 1, is the most well-known form of legionellosis, probably because of the fatalities. About 5% to 30 % of people who have Legionnaires disease die.

Where do the legionnella bacteria come from?

Legionella bacteria are common and can be found naturally in environmental water sources such as rivers, lakes and reservoirs, usually in low numbers. If the bacteria get into water systems used in buildings such as hotels, they can sometimes cause a risk to humans if people get exposed to them through air conditioning or air cooling systems or through contaminated water systems used for baths or showers etc.

How do you get legionnaires disease?

People become infected when they breathe in air that contains tiny droplets of water known as aerosols, inside of which are the legionella bacteria. If the bacteria get inhaled into the lungs they can cause infection.

Legionnaires disease is not transmitted through from water you drink that enters your stomach in the normal way Bacterium has to get into the lungs through breathing it. The illness is not spread from person to person.

What are the usual symptoms of legionellosis?

Patients with Legionnaires disease usually have fever, chills and a cough which may be dry or may produce sputum. Some patients also have muscle aches, headache tiredness loss of appetite and occasionally diarrhea. Laboratory tests may show that these patients kidneys are not functioning properly. Chest X-rays often show pneumonia. It is difficult to distinguish Legionnaires disease from other types of pneumonia by symptoms alone, other tests are required for diagnosis.

Persons with Pontiac fever experience fever and muscle aches and do not have pneumonia. They generally recover in 2 to 5 days without treatment.

The time between the patient’s exposure to the bacterium and the onset of illness for Legionnaires disease is 2 to 10 days, for Pontiac fever, it is shorter, generally a few hours to 2 days.

How do outbreaks occur?

Experience shows that outbreaks in hotels are mostly associated with hot or cold water distribution systems. If the bacteria is in the water in quantities that can cause infection, someone taking a shower would inhale the bacteria trapped inside the tiny aerosols that are created when the shower water hits the hard surfaces of the shower unit or bath. They may also be affected by other water systems that cause aerosols, for example whirlpool spas and fountains. In contrast large explosive outbreaks in the community are mostly associated with cooling towers. Cooling towers are devices used to cool buildings. They are also called “wet air conditioning systems” because the process of cooling air involves extensive contact between water and air thereby creating aerosols. When the legionella bacteria are present in these systems they can cause legionnaires disease. Air conditioning units that use water to cool the air can also pose a risk in hotels. However, many air conditioning systems are dry and these pose no risk for legionnaires disease. When an outbreak of legionnaires disease occurs the source may be found through two types of investigation. One collects information on the activities and where about of the patients with legionnaires disease to look for links between cases such as staying at or visiting the same places before they became ill. The other involves looking for the legionella bacteria in the suspected water sources and in clinical specimens from the patients. It the bacteria are found in both, specialised laboratory methods are use do see if they are of the same type.

What should be done to prevent legionellosis?

Improved design and maintenance of cooling towers and plumbing systems to limit the growth and spread of Legionella organisms are the foundations of Legionellosis prevention.

Factors increasing susceptibility

Age >50
Children rarely infected
Sex, males 3x more susceptible
Existing respiratory disease
Cancer, diabetes, surgery, alcoholism
Mortality rate approx. 12%
Hospitalised patients 25%
ged/immunocompromised up to 80%

Route of Infection

The principle route of infection is through inhalation of the bacteria into the lungs. Bacterium is carried in water of a particular droplet size. The risk is related to the number and type of Legionella in the water, Risk is increased with the density of the aerosol and the droplet size (Range 2-5 microns in diameter). No evidence of person to person transmission

Hazard Rating Factors Production Growth

Stagnant water, Temperature for growth (Range 20 °C to 60 °C), Below 20 °C the growth remains dormant. The range 20 °C – 45 °C favours growth, 37 °C optimum for growth, Above 60 °C the organisms can not survive, Contact time (the death rate is logarithmic with time for a given temperature).

Nutrients (Food): The presence of sediment, sludge, scale, organic material, iron oxide (rust) algae, amoebae and other bacteria. Note: Algal slime provides an ideal stable habitat for multiplication and survival of the organism. Water distribution pipe work fittings and materials used in the installation of the system.

Sources of Legionellosis

Cooling Towers
Spa's & Jacuzzi's
Ornamental Fountains
Water Sprinklers
Misting Machines
Clinical Humidifiers
Drilling/Grinding Machines
Dental Chairs
Car Washes