Complete lesson that covers Spread of diseases, Pathogens and barriers, Pathogens , Defences against pathogens, Immunity, Antigens & Antibodies, Active and Passive Immunity, Immune system disease, Vaccinations, Vaccines, Preventing the spread of disease, Controlling spread of diseases. Main ObjectivesDefine pathogen as a disease-causing organism Define transmissible disease as a disease in which the pathogen can be passed from one host to another State that the pathogen for a transmissible d