Transmission Tactics
As discussed on the Habitat page, Legionella pneumophila occupy many diverse water settings. This fact directly defines the methods by which the disease is transmitted to humans. The primary mode of infection is through the inhalation of contaminated aerosolized water droplets by a susceptible human being. The water then enters into the lungs where pulmonary macrophages overwhelm the bacteria. It is here that, rather than be destroyed, Legionella pneumophila proliferate. Because of this mode of contraction, water-aerosolizing devices such as humidifiers and showers are subjects of anxiety in the transmission of Legionella pneumophila to its hosts.
Another theory states that drinking contaminated water followed by aspiration leads to infection. In this method, when the organism enters the mouth it is stopped via cilia in the respiratory tract from entering the lungs. It is through aspiration that the Legionella pneumophila is able to side-step the cilia and fall into the respiratory tract where it will then hold on, invade and multiply.
For details regarding how Legionella pneumophila behaves once has been transmitted to its host go to the Pathogen Proliferation page!