1. Division of Infectious Diseases, Department of Medicine, University of California, San Francisco, CA 94143, USA
2. Department of Pathology, University of California, San Francisco, CA 94143, USA
3. Department of Medicine, University of California, San Francisco, CA 94143, USA
4. Institute of Microbiology and Virology, Riga Stradins University, LV-1007 Riga, Latvia
5. Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, SE-171 77 Stockholm, Sweden
6. D.I. Mendeleyev Institute for Metrology, 190005 St. Petersburg, Russia
7. Almazov National Medical Research Center, 197341 St. Petersburg, Russia
8. Department of Epidemiology and Biostatistics, University of California, San Francisco, CA 94143, USA
9. Division of Oral Epidemiology, University of California, San Francisco, CA 94143, USA