Transmission of Legionellosis

Transmission of the disease is by means of aerosols or atomised water droplets contaminating the bacteria.

Many processes can produce these small droplets of water including showers, taps, cooling towers and any other process where the surface of water is broken or agitated. Once airborne these aerosols can travel for long distances (miles if produced externally) and spread over a wide area.

If these are inhaled into the respiratory system then the bacteria hijack the human body’s own defence system, propagate and cause the infection. Transmission of the disease from human to human has never been documented and it must be stated that most people who are exposed to the bacteria do not become ill.

The factors that determine the morbidity of the disease are not yet fully understood, however, infection is more frequent in males than in females.

Also, the risk of Infection increases in the middle aged or elderly population, smokers or people with chest or respiratory conditions and anyone who may have a suppressed immune system.