Outbreak

There is no exact number of instances of disease that must occur for an outbreak to be declared. To determine if an outbreak has occurred, you must compare the number of illnesses reported over the last few months that were caused by the strain you are investigating with the number of illnesses reported over the same period of time that were caused by other strains of the same pathogen and species. If the number of illnesses reported that were caused by the strain you are investigating seems unusually high compared to the number of illnesses caused by other strains of the same pathogen and species, then an outbreak can officially be declared.