Legionnaires’ Disease

A Brief History

The first outbreak of the disease occurred at the 1976 Legionnaires Convention in Philadelphia. The bacteria that caused the disease was eventually isolated and calledLegionella Pneumophilla. This bacterium is responsible for 90% of all cases of legionella infections.

The Symptoms

Legionnaires’ disease begins with very general symptoms, including a headache or muscle ache. Symptoms worsen with a high fever and shaking chills. From here infected individuals become progressively more unwell, suffering from dry coughing and chest pains. Most patients go on to develop pneumonia, which sometimes requires hospitalization. Complete recovery can take several weeks and around 5-15% of known cases of Legionnaires’ disease have proved fatal.

Naturally Harmless

The legionella bacteria are found naturally in rivers, warm springs, streams, lakes and riverbanks. In their normal habitats legionella do not cause infections, however, once they have entered air conditioning units and water supplies of large buildings they can cause disease outbreaks.

In The Indoor Environment

The latest scientific thinking is that legionella bacteria infect people when inhaled into the lungs. This is why the research around the spread of Legionnaires’ disease has focused on building ventilation systems. The theory states that infected water is picked up and circulated via the heating and ventilation system. If these droplets are small enough, they can be inhaled by building occupants and thus enter the lungs.

Cooling Towers

Research has pin-pointed the danger areas as cooling towers. These towers are central part of large modern air-conditioning systems. They are used to cool water and dissipate unwanted heat to the atmosphere through water evaporation. It is here that the most care must be taken to ensure the bacteria have no chance to develop.

It is a Building Code requirement that bacteria levels in cooling towers are checked at least monthly. Contact Airlab for independent advice and sampling.

Disease Prevention

Regular monitoring and cleaning can greatly reduce the risk of legionella infections. A monitoring and maintenance programme will ensure that heating and air ventilation systems are clean and clear of bacteria. Hot water tanks, which might provide ideal conditions for the growth of legionella, should be cleaned. Water system should also be flushed out on a regular basis to prevent the water from stagnation.