Legionnaires’ disease (LEE-juh-nares) is a form of pneumonia caused by the bacterium Legionella pneumophila. A mild form of the disease is called Pontiac fever. Unlike Legionnaires’ disease, which affects only a small percentage of people who are exposed, Pontiac fever will affect approximately 90 percent of those exposed.
In addition, the time between exposure to the organism and appearance of the disease is generally shorter for Pontiac fever than for Legionnaires’ disease. Symptoms of Pontiac fever can appear within one to three days after exposure.
Legionnaires’ disease may occur sporadically in the form of community acquired pneumonia and in epidemics.
It is a respiratory infection acquired after inhaling Legionella pneumophila from mist from water sources such as whirlpool baths, showers, and cooling towers that are contaminated with Legionella bacteria.
The disease may be characterized by general malaise, chills and fever. People of all ages can get Legionnaires’ disease, but it primarily affects people with weakened or compromised immune systems, including those who are over age 65, those with lung disease and smokers and generally men more than women. Some people can be infected with the Legionella bacteria and have only mild symptoms or no illness at all.
Legionnaires’ disease is most frequently associated with persons with weak immune system. The disease has been associated with domestic hot-water systems in a number of outbreaks. Legionella can also proliferate in poorly maintained whirlpools, spa pools and associated equipment. Naturally, Legionella bacteria live in fresh water and are often found in hot tubs, air conditioning cooling units and fountains.
Since Legionnaires’ disease can have symptoms similar to those of many other forms of pneumonia, it can be hard to diagnose at first. Legionnaires’ disease is a serious illness and deaths may occur in approximately 10-15% of otherwise healthy individuals. Legionnaires’ disease is not contagious and cannot be transmitted from one person to another.
The disease was named after its discovery in a group of people attending an American Legion convention in 1976. Disease may develop from several days to two weeks after exposure. Symptoms typically disappear within two to five days. Disease is treatable with antibiotics. Legionnaires, disease is also more common in the summer months.
Legionellosis is the term that collectively describes infections caused by members of the Legionellaceae family.
Legionella can grow to dangerous levels in systems that store water, including ornamental water features. Water is the major environmental reservoir for Legionella. Legionella bacteria are protected against standard water disinfection techniques, by their symbiotic relations with later microorganisms (protozoa). Legionella is more resistant to chlorine and microbial biocides than other microorganisms.
In summary, Legionnaires’ disease is caused by Legionella bacteria. Legionella lives naturally in rivers, lakes, and reservoirs but can also be found in cooling towers and domestic water systems. Legionnaires’ disease can be contracted by inhaling in droplets of water containing the Legionella bacterium from water sources where there have been poor maintenance, problems with controlling the temperature of the water or where water has remained stagnant for some time.
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