Use of pulsed-field gel electrophoresis for investigation of a cluster of invasive group A streptococcal illness--Spokane, Washington, 1999.

On January 25, 1999, health officials in Spokane County, Washington (1999 population: 415,000), were notified of a fatal case of necrotizing fasciitis (NF) caused by community-acquired invasive group A streptococcus (GAS) infection. Although invasive GAS infection is not a reportable disease in Washington, Spokane health officials requested reports of additional invasive GAS cases from local hospital infection-control professionals and the medical examiner to identify other cases. This report describes a cluster of fatal illnesses caused by GAS in five residents of Spokane County and illustrates how investigators used pulsed-field gel electrophoresis (PFGE) to determine whether the cluster was unrelated sporadic cases or attributable to a common source.