Legionella and Legionnaires' Disease

Legionella disease was recognized after an outbreak in 1976 among people who went Philadelphia convention American Legion. The causative agent was identified named as Legonella which is caused Legionellosis infection. Legionellosis is caused in the differential diagnosis of patients showing a combination of neurological, cardiac and gastroinintestial symptoms. The most sources of infection are hot tubs, water used for drinking, hospitals, hotels etc. Bacterias and protozoas in the domestic and public hot-water systems tend to adhere to surfaces, creating microenviroments known as biofilms. Some microorganisms are not harmful for human healthy. Sometimes, transmission may occur through inhalation from the contaminated water can be caused infections.

Legionella Formation and Legionnaires Disease;

The origin of the genus Legionella bacteria is puddles, rivers and lakes. Some of the genus Legionella bacterias are found in the moist soil. The major source is water distribution systems in the buildings such as hospital, hotels&resorts. Other sources are humidifiers, cooling towers, swimming pools, air conditioners. Chemical disinfectant  (especially chlorine) are used to eliminate this bacterias, but it is not enough to ensure optimal conditions.

A temperature 20⁰ to 55⁰ Celcius is ideal for Legionella growth. These temperatures can be created suitable conditions for the formation of Legionella.

Legionella was discovered in 1976 which is caused Legionnaires disease. Legionella pneumophila is belonging to the family of Legionellaceae which can caused disease. The most symptoms of Legionnaires’ disease is cough, high fever, muscle aches and headaches. Most healthy people do not affect Legionella, but older people and people with a weak immune system become infected with Legionella after exposure. Its symptoms are similar to other disease, for this reasons specific tests are needed.

This bacterium is found in;

  • Shower baths and shower heads
  • Hot water storage units
  • Air conditioners and humidifiers
  • Decorative polls and fountains
  • Hot tubs and natural spas
  • Water cooling towers

Water storage tanks, cooling towers and some cold and hot-water systems are potential environment for the formation and growth of the bacterias. The water distribution systems should be avoided water temperatures are between 25°C-45ºC to prevent Legionella colonization. In many systems are not controlled because of the nature of the system.

Transmission of Legionella to People

Legionella is spread out by sanitary systems and air conditioning. Particularly, this bacterias family is encountered in hotels, hospitals, business centers such as in large systems and plants. The transmission of Legionella to people is occured primarily through inhalation of aerosols contaminated with Legionella. Water is the major natural reservoir for Legionella and bacterias are found in many different environments such as hospitals, nursing homes, dental applications, hotels&resorts etc. Regulatory aspects of controlling Legionella in water systems and preventing disease should be considered because of Legionella.

Controlling of Legionnaires' Disease

DVGW Worksheet W551 (German Technical and Scientific Association for Gas and Water) makes suggestions for operating drinking water systems to make certain of excellent drinking water qualities. Various disinfection processes are described at this worksheet. According to Worksheet W551, the water must be maintained to temperature of minimum 60°C at the water outlet. The temperature of the water in the system is not exceeded by more than 5K compared to the temperature of the water at the outlet of the drinking water heater at the circulation system. Otherwise, disinfection is only necessary if the contamination is more than 100CFU/100 ml at the tap points. The water contamination value is higher than 10000 CFU/100 ml should be taken precautions.

Regulation on controlling of Legionnaires disease is published on May 2015 in the official journal. This regulation is about that ensuring against Legionnaires disease. It is specified that the actions to be taken by the people. Summurized of the regulation is about;

  • Duties and responsibilities are specified to prevent disease
  • Duties of the referance laboratory
  • Duties and responsibilities of the laboratory which is analyzed the samples
  • Cleaning and disinfection applications