On August 30, 2013, the Colorado Department of Public Health and Environment (CDPHE) was notified by several hospitals of an increase in the number of patients visiting their emergency departments (EDs) with altered mental status after using synthetic marijuana. Synthetic marijuana is dried plant material sprayed with various synthetic cannabinoids and smoked as an alternative to smoking marijuana.

In response to the increase in ED visits associated with the use of synthetic marijuana, CDPHE asked all Colorado EDs to report through EMResource (a web-based reporting system) any patients examined on or after August 21 with altered mental status after use of a synthetic marijuana product. Serum and urine specimens from patients also were requested.

On September 8, CDPHE, with the assistance of CDC, began an epidemiologic investigation to characterize the outbreak, determine the active substance and source of the synthetic marijuana product, and prevent further morbidity and mortality. Investigators reviewed ED visit reports submitted through EMResource and medical charts.

A probable case was defined as any illness resulting in a visit to a Colorado ED during August 21–September 18, 2013, by a patient with suspected synthetic marijuana use in the 24 hours preceding illness onset. Of 263 patient visits reported to CDPHE through EMResource (214) and other means, such as e-mail and fax (49), a total of 221 (84%) represented probable cases.