1. Department of Emergency Medicine, University of Massachusetts School of Medicine, Worcester, Massachusetts.
2. Department of Emergency Medicine, University of Iowa, Iowa City, Iowa.
3. Department of Microbiology, University of Iowa, and Pathology—C606 General Hospital, Iowa City, Iowa.
4. Department of Pathology—C606 General Hospital, Iowa City, IA 52242-1009.
5. The Surveillance Network, Focus Technologies, Inc., Herndon, Virginia.