Legionellosis is an infection of the lungs caused by bacteria called Legionella. The bacteria can cause two types of infections: Legionnaires’ disease, which is a severe type of pneumonia, and Pontiac fever, which is a milder, influenza-like illness.

How is legionellosis spread?

Legionellosis is not spread from person to person. The bacteria that causes the infection lives in the environment in warm water. Less commonly, soil (such as potting soil) has also been implicated in cases of legionellosis. People become ill when they breathe in water droplets contaminated with these bacteria. Most cases are usually seen during the warmer months of the year.

Some common sources of Legionella are:

  • Commercial cooling towers, heating, ventilation and air conditioning systems
  • Large water systems in hotels (therefore travel is a common risk factor), hospitals and nursing homes 
  • Hot tubs, whirlpools, and public spas
  • Showers, especially those used outside the home or those that have not been in regular use
  • Decorative water fountains
  • Hot water tanks
  • Humidifiers
  • Creeks and ponds and the soil from their banks
  • Potting soil and composting material used for gardening
What are the symptoms of legionellosis?

Pontiac fever is a mild respiratory illness lasting about 1 to 3 days. Symptoms usually start within 1 to 2 days after contact with the bacteria and include a fever, headache, muscle aches and tiredness; less often there may be cough or nausea.

Legionnaires’ disease is a severe form of pneumonia which is sometimes fatal. Symptoms usually start within 5 to 6 days (can be from 2 to 10 days, and rarely as long as 3 weeks) after contact with the bacteria and include fever and chills, muscle aches, headache, cough, shortness of breath, weakness, diarrhea, loss of appetite and confusion. Delays in diagnosis may occur because symptoms are similar to other forms of pneumonia.

Typically, healthy people don’t become ill, or they develop the milder form of the disease. Those most at risk of developing life-threatening infections are adults over 65, persons who smoke or are heavy alcohol users, and those who have lung disease, kidney disease, weak immune systems, or diabetes.

What is the treatment for legionellosis?

Most cases of legionellosis presenting as Legionnaires’ disease are successfully treated with antibiotics. Persons with serious underlying health problems may take a long time to recover even after treatment. In rare cases, death can occur. Pontiac fever usually does not require antibiotic treatment. Treatment for legionellosis is the decision of a healthcare provider.

Are there any restrictions or special considerations for people ill with legionellosis?

Generally, people can return to work and child care when they are fever free and feeling well enough to return. Since legionellosis is not spread from person to person, there is no risk of spreading the infection to others.

How can I protect myself against legionellosis?

To prevent becoming ill with legionellosis or to prevent the growth of legionella bacteria:

  • Follow manufacturers’ directions for regular maintenance and cleaning of all water devices such as hot tubs, whirlpools, humidifiers, air conditioners, fountains, etc.
  • Keep your home water heater at a minimum of 60°C to help prevent the growth of Legionella. However, to reduce the risk of scalding, water at the tap should be no higher than 49°C. A qualified plumber can install mixing valves to control the tap water temperature.
  • Avoid using tap water in respiratory therapy devices such as CPAP machines. Always follow the manufacturer’s directions for water use with these devices.
  • Avoid smoking to decrease your own personal risk.
  • Building managers should have water safety plans that include maintenance, monitoring, and cleaning of water systems.
What is Ottawa Public Health’s (OPH) role?

All cases of legionellosis must be reported to public health for follow up. Once a laboratory report of this illness is received, OPH interviews the individual, provides education and follows up with the person’s healthcare providers where appropriate. If a common source of illness is identified, OPH will provide follow-up investigation.

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