When investigating a disease outbreak, the initial step is to find and identify cases, making sure that those classified as anthrax truly have the disease.  The onset times of cases are presented in a graph, showing cases by various subdivisions such as age, gender and location. The population at risk must be identified, namely the group from which the cases arose. A hypothesis is then generated and tested to determine if the population and cases explain the outbreak.  Rather than featuring a complicated statistical analysis, the findings of the American Anthrax Outbreak of 2001 are presented as graphs, showing how useful onset times can be for clarifying the likely cause. 

The first item is a list of 22 cases plus one person who was removed on December 7 due to lack of anthrax confirmation.  This list provides the data for the cases included in the subsequent graphs.  Next is a time graph of the first 21 cases that CDC published once the distribution became clear.  Third is the distribution of suspected and confirmed cases, following by the distribution of inhalational and cutaneous anthrax. Thereafter, the items include onset times for cases that lived and died, cases by age, gender, and location where the infection took place. Finally with the hypothesis that spore-infected mail is the culprit, the next item presents the onset time by potential source of exposure.  A concluding graph is for clinicians, with information on the time course of the 11 cases of inhalational anthrax.