Legionella is a genus of gram-negative bacteria capable of causing respiratory diseases such as pneumonia (referred as the Legionnaire's disease) and pontaic fever with flu-like symptoms. The bacteria have over 40 species and one of them, Legionella pneumophila, was discovered in a 1976 pneumonia outbreak at an American Legion Convention held in Philadelphia, which have cost over 20 human lives.
Often transmitted through inhaling contaminated aerosol particles, Legionella could be found in the natural environment such as in soil and artificial water systems like hot water tanks, cooling towers and spas. Smokers, the elderly and people with impaired immunity are most susceptible to the bacteria. Legionnaire’s disease was also found to be more common among males and is not transmissible among humans.
Symptoms of the disease may include high fever and chills, headache, muscle pain, cough, diarrhea and sometimes mental confusion. Severe pneumonia leading to collapse of the respiratory system could also result. The disease could be treated by antibiotic such as erythromycin.