1. Division of Viral and Rickettsial Diseases, National Center for Infectious Diseases, Centers for Disease Control and Prevention, 1600 Clifton Road NE, Mailstop G-17, Atlanta, GA 30333, USA1
2. Viral and Rickettsial Diseases Laboratory, California Department of Health Services, Berkeley, CA 94704, USA2
3. Department of Laboratories, Directorate General of Health Affairs, Ministry of Health, 113 Muscat, Oman3