1. Danish Institute for Food and Veterinary Research, Copenhagen, Denmark;
2. Centers for Disease Control and Prevention, Atlanta, Georgia, USA
3. Centers for Disease Control and Prevention, Atlanta, Georgia, USAAtlanta Research and Education Foundation, Atlanta, Georgia, USA
4. US Food and Drug Administration, Laurel, Maryland, USA
5. Ministry of Public Health, Bangkok , Thailand
6. Centers for Disease Control and Prevention, Atlanta, Georgia, USAStatens Serum Institut, Copenhagen, Denmark