1. University of Southern California, Los Angeles, California, USA;University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA;
2. University of Copenhagen, Hvidovre, Denmark;
3. National Institutes of Health, Bethesda, Maryland, USA;
4. University of Cincinnati, Cincinnati, Ohio, USA;
5. Centers for Disease Control and Prevention, Atlanta, Georgia, USA;
6. University of California San Francisco, San Francisco, California, USA;
7. Centers for Disease Control and Prevention, Fort Collins, Colorado, USA