| The Legionella organism is a gram negative, rod shaped bacterium that can cause pneumonia (Legionnaires' Disease) or a flu like illness (Pontiac fever). It was first identified and recognized as causing disease during the outbreak that occurred in conjunction with the American Legion Convention in Philadelphia in 1976. There are over 40 species of Legionella and 18 of those can cause disease. It is estimated that the species Legionella pneumophila causes most of the infections. |