1. aMassachusetts General Hospital, 100 Blossom Street, Boston, MA, 02114, United States of America (USA).
2. bUniversity College London, London, England.
3. cNational Center for STD Control, Chinese Academy of Medical Sciences and Peking Union Medical College Institute of Dermatology, Nanjing, China.
4. dLondon School of Hygiene and Tropical Medicine, London, England.
5. eUniversity of North Carolina School of Medicine, Chapel Hill, USA.