Epidemiology has its limits at the point where an inference is made that the relationship between an agent and a disease is causal ( general causation ) and where the magnitude of excess risk attributed to the agent has been determined ; that is , epidemiology addresses whether an agent can cause a disease , not whether an agent did cause a specific plaintiffâ s disease . Epidemiology has its limits at the point where an inference is made that the relationship between an agent and a disease is causal ( general causation ) and where the magnitude of excess risk attributed to the agent has been determined ; that is , epidemiology addresses whether an agent can cause a disease , not whether an agent did cause a specific plaintiffâ s disease . ''