Legionella: a health risk
But let’s go step by step.
What is Legionella?
Legionella is a gram-negative aerobic bacteria. More than 50 species have been identified, divided into 71 serum groups.
The most dangerous one is Legionella Pneumophila: about 90% of Legionellosis cases have been linked to it.
Why is it called Legionella?
Legionella acquired its name after an acute outbreak that sickened 221 persons attending a convention of the American Legion (an association of U.S. military veterans), causing 34 deaths. The convention occurred in a hotel in Philadelphia in 1976.
The “new” bacteria, called Legionella, was found in the air conditioning system of the hotel where the veterans were staying.
How is it transmitted? What are the health risks?
When this comes into contact with the lungs of subjects at risk, legionellosis occurs, often mistakes for pneumonia in the past.
What does Legionella entail?
• Pontiac fever: the average incubation period is 24-48 hours, similar to a flu which will resolve in 2-5 days and has no pulmonary involvement.
• Legionellosis: the average incubation period is 5-6 days, with serious pulmonary involvement. In addition to malaise, headaches, coughs, fever, neurological and cardiac symptoms and various complications may be present. In several cases it can be lethal. The disease is lethal in 5-15% of cases.
Where the problem exists and under what conditions
• Water/sanitary installations, domestic hot water, domestic cold water (taps, showers, etc.)
• Spas, pools and rehabilitation pools
• Decorative fountains
• Medical appliances for respiratory treatments
• Cooling towers
• Birthing tanks
• Air conditioning systems and humidification
• Dental offices
• Fire extinguisher sprinkler system
The optimal water temperature for development and infection is between +20 and + 50 °C. Moreover, the presence of nutritive elements (as biofilm, sediment, limestone), facilitates the development of the bacterium.
Treatment techniques against Legionella
There is no water treatment without negative consequences. Nor there is a treatment that guarantees the total elimination of all risks.
There are short-term and long-term measures.
Short-term measures are good practices of maintenance of a water system to prevent and contain contamination:
• Descaling of less worn elements by immersion in acid solution. Disinfection for at least 30 minutes in cold water containing at least 50 mg/L of free chlorine.
• Replacement of joints, gaskets, tap filters, shower heads and worn flexible pipes to the showers as well as any other element of discontinuity.
The frequency of replacement usually depends on the water characteristics. For example, major is the water hardness, more frequent will be the formation of limestone hence the wear of the hydraulic elements.
Long-term measures are:
• Thermal treatment
• Silver copper ionization
• Hyper chlorination
• U.V. irradiation
• Chlorine dioxide hydrogen peroxide with silver salts
For all these long-term measures, we have developed a series of tools and tips, which can help you in preventing and controlling Legionella. You can find them in our Technical Book “Control Systems and Legionellosis Prevention”.
Download it for free.
