About Legionella

Legionella and water environments

Legionella bacteriun, at low levels, is widely present in water environments. The problems of infections caused by this pathogen appears when there is a high concentration of that organism within the aerosols produced by contaminated water.

Legionella is widely extended in water natural environments (rivers, lakes, termal waters, etc) in low concentrations and the can survive in very different environmental conditions. That the concentration increases, to pose risk to people, must go to settle, mainly through the distribution networks of drinking water, water systems built by humans, such as cooling towers and water distribution systems, sanitary, where temperature conditions are suitable for multiplication (25-45 º C), physical protection and proper nutrients.



The Legionnaires' disease occurs when susceptible people inhale an aerosol containing Legionella, not when you drink water containing Legionella (showers, hot water taps, hot tubs and cooling equipment such as cooling towers and air conditioners, produce aerosols). Some types of Legionella can cause a type of pneumonia called Legionnaires' disease. Legionella can also cause much less severe disease called Pontiac fever. Pontiac fever symptoms can include muscle aches, headache, cough, nausea, dizziness and other symptoms. Pontiac fever is caused by the same bacteria but without lung involvement.

Since its initial identification in 1977, there have been numerous cases of legionnaire's disease in Canada, USA, France, Italy and Spain among other countries. 15% of cases can be fatal, and this percentage in bacterial pneumonia in 2000 is very high.

In Spain, since 1980 there have been a total of 48 outbreaks of legionnaires' disease, which affected 789 people, apart from the 1,358 sporadic cases since 1997.


Information resources:

The organism

The Legionella species are gram negative. They were originally described as agents of respiratory tract infections studying an outbreak of pneumonia among men who in 1976 attended a convention of American Legionnaires in Philadelphia, USA. It was found that the organism grew in the cooling towers and spread through air conditioning systems of the convention center. Those most affected were individuals who had abnormalities in pulmonary clearance, such as smokers. The Legionella are difficult to grow in culture and rich nutrients required for growth and activated charcoal in the agar to reduce inhibitory substances such as superoxide radicals and peroxides, which are formed when exposed to light.

Where does

  •      In general in the drops of water at a temperature between 20 and 40 º C.
  •      Building cooling towers for air conditioning.
  •      Humidification systems, commercial and domestic.
  •      Hot water pipes.
  •      Public source.
  •      Other systems of movement warm-temperate water.

In short, the primary factors to consider favoring the multiplication of Legionella in water cooling towers are:

  • High temperatures, especially in the summer months.
  • DIRT, which may encourage the presence of other microorganisms (bacteria and protozoa) that favor the multiplication of Legionella and its proper nutrients.
  • Inadequate materials, such as wood and cellulose-based general.
  • CORROSION AND SCALING, due to improper maintenance of the facility and contribute to the growth of Legionella through the supply of nutrients (iron, phosphates, etc..) and favoring the quartering of the bacteria, thus reducing the effectiveness of the cleaning and disinfection.

( https://www.microbelibrary.org/index.php/library/2-associated-figure-resource/556-enlarged-view)

How to Prevent It

Maintenance of cooling tower systems, washing and sterilization of deposits of water 2 times per year. The domestic hot water tanks should be treated equally. Water tanks outdoors should be reviewed periodically.

The study of the sources of infection associated with the emergence of human cases of legionnaires' disease has led to identifying a number of buildings and facilities from the outbreaks which spreads the bacteria causing the infection. Hot water systems, both hot and cold, air conditioning ducts, cooling towers, mechanical breathing apparatus, heated pools and even water features have been clearly implicated in the production of disease. Current knowledge on the biology of bacteria can develop a set of basic principles to minimize the risk of Legionella colonization, and multiplication and dissemination.

Prevention of Legionella contamination can take place as early as the design of facilities and, especially, in the maintenance phase of the same. Moreover, when a specific facility is involved in the production of disease with clear epidemiological and microbiological criteria, the facility should be treated - rigorously sanitized, and control.

Legislation in Spain

The government has completed the development of legislation to prevent legionella national level, but communities have transferred competence in this area. The new Act has been filed as a Royal Decree and has been approved by the Council of Ministers on 27/07/2001.

Among other things, this new law will allow the regions to have more ability to bind to specific locations such as heated swimming pools or cooling towers, to pass regular checks to prevent further outbreaks of the disease.

Details on how to clean, disinfect and maintain the facilities to which we refer is found in the report "Guidelines for Prevention of Legionella in facilities." Other health measures on the merits of monitoring, controlling and even close microbiologically facilities involved in the occurrence of cases or outbreaks, are the responsibility of the health authority and have been widely developed in the recent publication of the Ministry of Health Recommendations for prevention and control of Legionnaires'

(Recommendations for the prevention and control of legionellosis. Technical Secretariat of the Ministry of Health. 1999. ISBN 84-7670-507-7. Price 800 pesetas / 4.81 euros. This document is the result of a joint expert in epidemiology, microbiology, environmental health, preventive medicine or sanitary engineering. Its purpose is to facilitate the adoption of measures for the staff involved in the installation, maintenance, inspection and medical treatment facilities capable of transmitting legionellosis. The recommendations are aimed at personal working for public health authorities and health care, engineers, architects, installers and maintenance companies and treatment facilities. A wide range of professionals, all involved in the prevention of legionellosis.)

Madrid, Catalonia, Valencia and Galicia have special rules to curb the spread through air conditioning systems, although all regions have transferred competence of health inspection.

The pioneer rule was published by the Department of Health and Social Services for the Community of Madrid on June 11, 1998 as a result of the infections occurred in 1996 in Alcalá de Henares, where 11 people died and 246 were affected by the outbreak. ORDER 1187/1998 of 11 June, the Ministry of Health and Social Services of the Community of Madrid by regulating the hygienic criteria to be met by the apparatus of mass transfer water in air flow and humidification devices for the prevention of Legionnaires' disease

The same law says that chlorine is the best treatment for preventive disinfection of equipment.

In Valencia, with repeated outbreaks of legionella reported in the Hospital de Alcoy, the Ministry of Health issued a decree in December 2000 which regulates "the hygienic conditions" that must meet the air conditioning equipment with emission of aerosols prevent legionellosis.

The Catalan government was forced to legislate in December 2000 with urgent technical and sanitary conditions of air conditioners after the legionella outbreak in Barcelona, ​​which affected 49 people in La Barceloneta.

In Galicia was published in January, the decree regulating health criteria for the prevention of legionella contamination in the thermal installation.

In La Rioja is collected in theRoyal Decree 664/1997, of May 12, protection of workers from risks related to exposure to biological agents at work, measures of protection against legionella at the workplace.

Situation in Murcia

Although there Murcia community legislation on analysis of these cooling towers, yes there is a standard protocol and review maintenance of these facilities. That rule is not mandatory. To search for possible sources of infection, on Sunday, a helicopter flew over the city taking photographs. The potable water network in the city of Murcia is ruled out as source of infection. The City Council held from Saturday, the water from public sources as a precaution.


Information resources

Consejerías de Sanidad de las Comunidades autónomas


  • European working group for Legionella Infections. (EWGLI) Grupo de trabajo creado en 1986 constituido por un grupo de epidemiólogos y microbiólogos con el objeto de promover la colaboración en el trabajo sobre la legionelosis y sus agentes etiológicos. http://www.ewgli.org/
  • Legionella FAQ´s. Fuente (EWGLI)
  • Progress Report on the Network of epidemiological surveillance and control of communicable diseases in the European Community. COM (2000) 471 final.Informe status on the network of epidemiological surveillance and control of communicable diseases
  • The legionella experts http://www.legionella.org/
  • Legionella Genome project http://microbiology.columbia.edu/shuman/projects.html
  • Information, questions to experts, books, reports, seminars and consulting services Leginella and all systems of prevention and treatment and water facilities http://www.hcinfo.com/
  • Travel associated legionnaires’ disease in Europe in 1999. Euroroundup Vol 6 / No 4 (April 2001).
    Full paper: http://www.eurosurveillance.org/ew/2000/000420.asp

NOTE: All the information in this section about legislation and regulations are pure informational and its subordinate to the published in Official Journals.