Airborne and aerosol transmission are not the same. Airborne transmission is defined as the spread of disease caused by particles containing pathogenic microorganisms (diameter less than or equal to 5 micrometers) that are suspended in the air and move with the air. Aerosol transmission, on the other hand, is defined as solid or liquid particles (1 nanometer to 100 micrometers in diameter) containing pathogens mixing in the air to form an aerosol, which is inhaled by the human body and leads to infection, resulting in the spread of disease. Aerosol transmission is a form of airborne transmission, but airborne transmission is not necessarily aerosol transmission. For example, droplets form dust when they fall to the ground, and when disturbed the dust is lifted up and suspended in the air and inhaled by susceptible persons, resulting in infection, is called dust transmission, a form of airborne transmission, but cannot be called aerosol transmission.