Legionnaire’s Disease was first named in 1976, when veterans attending an American Legion conference came down with a mysterious pneumonia. It was identified as caused by a previously unidentified bacteria that flourishes in soil and water, and is often found in water storage facilities and cooling towers. Scientists named the bacteria Legionella pneumonphila. Although the incidence of Legionnaire’s worldwide is unknown, it had a resurgence in summer 2015 in the United States, with outbreaks in New York, Illinois, and California.
A common way for Legionella to travel is through contaminated aerosols. It is often transmitted in hospitals through wound infections. The bacteria lives in water storage facilities that are poorly maintained in homes, industrial sites, shopping centers, and hotels. There is no indication the bacteria is ever transmitted from person to person.
An article in the Human Healthy Project explains the way in which it attacks the human body:
…Legionella are often parasites of amoebas, which are single-celled organisms with pseudopods used to feed and move. Essentially, they are one of many amorphous blobs in water that swim around and eat things. In a human body, macrophages share the most resemblance to amoebas. After all, macrophage translates to “big eaters” in Greek according to Wikipedia. I think of them as Pac-man, except instead of yellow pellets they ingest foreign pathogens and dead particles. When a macrophage ingests whatever it finds (in this case, bacteria), the pathogen becomes trapped in a compartment called the “phagosome”. Usually, phagosome will combine with “lysosome”, a separate compartment with enzymes to digest and kill the pathogen–like a stomach pouch with digestive enzymes and acid secreting cells.
Legionella prevents the fusion of phagosome with lysosome, and turns the macrophage into a lovely home. Once they reach high numbers, they will form pores to exit the macrophage and move onto the next target, much like they do in amoebas. Both the macrophage and amoebas are dead as a result of the process. In Legionnaire’s disease, Legionella affects macrophages in the lungs. Once the bacteria reach high numbers, high inflammatory response occurs as the body’s defense, both build up causing pneumonia symptoms.
The same bacteria that causes Legionnaire’s disease also causes Pontiac fever. Pontiac fever develops in 95 percent of the people exposed, but it is a self-limiting disease, and does not usually involve pneumonia. Symptoms first appear within a day or two, and usually resolve within two to five days. It is rarely fatal. The symptoms include high fevers, chills, diarrhea, headache and other flu-like manifestations. Treatment focuses on relieving the symptoms.
Legionnaire’s disease develops in a much smaller percentage of infected persons. The incubation period ranges from two to 10 days, and the illness can last for weeks. It has no signature symptom, but there is a general malaise and anorexia. After that, some patients develop a cough (with or without blood), and possible chest pain and gastrointestinal distress. Nearly half of patients will experience neurological symptoms such as delirium, disorientation and tremors. Most people have fever with chills. Without treatment, the disease can progress to respiratory failure, failure of kidneys and other organs. Legionnaire’s can be fatal to 40 to 80 percent of patients. Treatment is by antibiotics.
The best way to prevent Legionnaire’s disease is to maintain water systems and ensure access to clean water. The bacteria cannot survive in water temperatures of 70 degrees centigrade and greater, and cannot reproduce at temperatures below 20 to 25 degrees centigrade. Chlorine, hydrogen peroxide, copper/silver ionization, anodic oxidation, UV penetration, and filters are also aids in prevention.