What it is:

  • Legionella are tiny rod-shaped bacteria.
  • There are over 40 known species of Legionella.
  • Legionella pneumophila is the cause for most human infections.
  • The pneumophila was first discovered following a pneumonia outbreak at the Convention of the American Legion in Philadelphia in 1976.
  • Pontiac fever and Legionnaires' disease are the two forms of Legionellosis.

Occurrence:

  • The Legionella bacterium are known to occur naturally in soil, surface fresh water, groundwater, marine surface water and potable water.
  • Legionella often proliferate in biofilms in plumbing where they become inaccessible to chlorine residuals.
  • It thrives in warm water (25-50°C) that is stagnant and has been found in re-circulating hot and cold water systems in hospitals, hotels, factories, public buildings, cooling towers and homes.

Health effects

  • The general population can be fairly resistant to infection.
  • Those with the best chance of picking up the disease are elderly, hospital patients on respiratory therapy, persons on corticosteroids or other immunosuppressive drugs and those with diabetes and end-stage kidney disease.
  • The disease is usually transmitted by the inhalation of an aerosol of tiny water droplets that contain the bacterium.
  • Symptoms of Legionnaires' disease include: Loss of appetite, muscle pain, headache, fever, cough, confusion, chills, nausea, diarrhea, vomiting, chest pain, difficulty breathing and disorientation.
  • Legionnaires' disease costs the U.S. healthcare system between $101 million and $321 million annually according to estimates by the U.S. Centers for Disease Control and.

Regulation:

  • The U.S. Environmental Protection Agency's (EPA) has set a Maximum Contaminant Level Goal (MCLG) in drinking water for Legionella at zero.

Water treatment:

  • To disinfect the entire water plumbing system you can try hyper-chlorination, thermal (superheating and flushing), chlorine dioxide or copper-silver ionization.
  • Drinking water treatment will kill Legionella but there is a chance that recontamination could occur during distribution and in the plumbing.

Sources: Centers for Disease Control and Prevention, U.S. Environmental Protection Agency (EPA), Water Research Foundation, World Health Organization.