1. Wisconsin Viral Research Group, Milwaukee, WI 53226, USA.
2. Open Medicine Institute, Mountain View, CA 94040, USA.
3. Blood Systems Research Institute, San Francisco, CA 94118, USA.
4. Department of Laboratory Medicine, University of California, San Francisco, San Francisco, CA 94143, USA.
5. Department of Medicine, Hematology/Oncology Division, University of California, San Francisco, San Francisco, CA 94143, USA.
6. Abbott Laboratories, Abbott Park, IL 60064, USA.