Defining outbreak: breaking out of confusion.

In the last two decades, emergence and re-emergence of infectious diseases have amplified the use of emotionally charged terms like "outbreak," "epidemic," and "pandemic" in the life sciences literature, the news media, and clinical practice. For instance, "outbreak" sounds like a scientific term, yet has quite a variety of uses. Its precise meaning is not universally understood, except that "outbreak" always refers to something positive in number and negative in perception. The many dimensions of the health field would benefit from a concerted effort to strengthen the definitions of key terms. The development of public health policy is an art form, aimed at some desired population health outcome, requiring a strong adherence to reliable scientific data. Although many different factors affect the adoption of interventions to promote health and curb disease, the closer the formulation of public health policy to scientific findings and terms, the more likely the goal intended will be reached.