Translations:Basic Field Epi: Participants' Workbook/124/en
Progression of an infectious disease in a population showing a single infected animal (black circle), susceptible animals (outline with no shading) and immune animals (gray shading). The infected animal is shedding agent and exposing either susceptible animals (no shading) or immune animals (shading) to infection. If the infectious animal only encounters immune animals (see image on the right) there will be no disease transmission.