Legionnaire’s Disease
Legionnaire’s Disease, also known as legionellosis is a lung-related infectious disease that is known to be caused by a bacterium of the genus Legionella.  The vast majority of cases of Legionnaire’s disease are caused by Legionella pneumophila—a water-based microorganism that lives in especially warm environments.
There are two basic forms of Legionnaire’s disease:

• Plain Legionnaire’s disease that is also known as Legion fever.  It produces pneumonia and is the more severe form of the disease.
• Pontiac fever, which is caused by the same organism but leads to a mild respiratory illness that is more like influenza than pneumonia.

The history of Legionnaire’s disease began in July 1976 when a number of people at a convention came down with a mysterious pneumonia in Philadelphia.  By January of 1977, the organism was identified as a bacterium no one knew about.  It was named Legionella. 
Nowadays, about 8000-18000 people come down with Legionnaire’s disease every year in the US. Again, the disease can be mild or severe.   Outbreaks of the disease often receive a lot of media attention although there are plenty of cases that are isolated and involve only one or two victims.  Most outbreaks occur in the summer and early autumn but cases can occur throughout the year.  The fatality rate for the condition is about 5 to 30 percent, depending upon the outbreak. 
Symptoms of Legionnaire’s disease include the onset of a fever, chills, coughing (which can be dry or productive), muscle aches, headaches, fatigue, poor appetite, ataxia (poor coordination) and sometimes diarrhea and vomiting.  The disease affects the functioning of the kidneys, liver and electrolytes.  Low sodium is a common finding.  The Chest XRAYS reveal bilateral pneumonia that looks a great deal like other kinds of pneumonia.  Sufferers of Pontiac fever exhibit muscle aches and fever but no pneumonia.  The disease lasts 2-5 days and resolves without any specific treatment.  It takes about 2-10 days to come down with the symptoms of Legionnaire’s disease from the time of exposure.
Diagnosis
Sufferers of the disease are generally middle aged and smokers who have a baseline chronic lung disease.  Patients who are immunocompromised are at a higher risk of getting pneumonia from Legionella.   The best tests for the diagnosis of this disease is the detection of the bacterium in sputum samples or high antibody levels to Legionella in blood samples obtained 3-6 weeks apart.  Legionella antigens can show up in urine samples as well. 
Treatments
Antibiotics in the form of quinolones and macrolides have proven to be the best choices for the treatment of Legionnaire’s disease.  Tetracycline is also a good choice for an antibiotic.   Some doctors add rifampin to one of the above antibiotics in more severe cases of the disease.  The use of these antibiotics has reduced the mortality rate to 5% or less. 
There is a great deal of oxidative stress in Legionnaire’s disease and the body’s defenses against the reactive oxygen species are less than what is necessary.  For this reason, substances such as glutathione which are antioxidants can help balance the redox status of the lungs. 
Transmission
Legionnaire’s disease usually occurs after inhaling an aerosol containing the bacterium Legionella.  The particles can come from any infected water source and transmission is worse in areas that are poorly ventilated.  Cooling towers can cause the disease in industrial areas.  Large air conditioning systems can be a cause of the disease.  Even ice making and misting equipment can be causes.  Outdoors, ornamental fountains can harbor Legionella.  The disease is especially associated with hotels, hospitals and cruise ships with poorly maintained cooling systems.  One type of Legionella is found in compost and soils and is transmitted through the dusts of these soils.