1. Clinical Investigation Facility, David Grant USAF Medical Center, 101 Bodin Circle, Travis Air Force Base, California 94535
2. Laboratory of Experimental Virology, Department of Medical Microbiology, Center for Infection and Immunity Amsterdam, Academic Medical Center, University of Amsterdam, 1105AZ Amsterdam, The Netherlands
3. D. I. Ivanovsky Institute of Virology, Russian Academy of Medical Sciences, 123098 Moscow, Russia
4. Viral and Rickettsial Disease Laboratory, California Department of Health Services, 850 Marina Bay Parkway, Richmond, California 94804