1. Rickettsial Zoonoses Branch and Centers for Disease Control and Prevention, Atlanta, Georgia, USA.
2. Bacterial Special Pathogens Branch, Centers for Disease Control and Prevention, Atlanta, Georgia, USA.
3. Division of Cancer Epidemiology and Genetics, National Cancer Institute, Rockville, Maryland, USA.
4. Digestive Diseases Research Institute, Tehran University of Medical Sciences, Tehran, Iran.
5. Department of Biology, School of Computer, Mathematical, and Natural Sciences, Morgan State University, Baltimore, Maryland, USA.