1. U.S. Naval Research Laboratory, Center for Bio/Molecular Science and Engineering (Code 6910), 4555 Overlook Avenue SW, Washington, D.C. 20375, Centers for Disease Control and Prevention, National Center for Infectious Diseases, 1600 Clifton Road, Atlanta, Georgia 30333, Center for Bioresource Development, George Mason University, 4400 University Drive, Fairfax, Virginia 22030-4444, and Nova Research, Incorporated, 1900 Elkin Street, Suite 230, Alexandria, Virginia 22308