1. Rickettsial Zoonoses Branch, Division of Viral and Rickettsial Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia.
2. Pasteur Institute of Epidemiology and Microbiology, St. Petersburg, Russia.
3. St. Petersburg Center for Epidemiological Surveillance, St. Petersburg, Russia.
4. Center for Epidemiological Surveillance, Novgorod, Russia.
5. Center for Epidemiological Surveillance, Arkhangel'sk, Russia.