The transmission mode of Legionella from its source was analyzed by microscope and fluorescence Quantitative Polymerase Chain Reaction (qPCR). The Legionella removal efficiency by water surface was 94.5%, and Legionella had difficulty in penetrating through the surface of the water membrane. A deflection point at the interface between water and air indicated a cluster of Legionella that was bonded to the contact surface by some unknown emplastic media. The emplastic media could stick firmly on glass and Legionella like glue. Force analysis showed that the surface tension of water is 106 orders of magnitude larger than the net force from the sum of the buoyancy and the weight of Legionella, and revealed that the surface tension of water is so large that a Legionella bacterium cannot break away from the water surface membrane and escape. The qPCR results showed that no Legionella was found in the air from a Legionella incubator or the Legionella laboratory. The results demonstrate that Legionella cannot be transmitted to people through water vapour or aerosol. The experimental results also indicate that water was able to remove most Legionella bacteria.
Keywords: Legionella; aerosol; membrane; qPCR; vapour.