1. George Mason University, Manassas, VA 20110, USA.
2. Queensland University of Technology, Brisbane, Queensland 4000, Australia.
3. Universidad Peruana Cayetano Heredia, Lima 31, Peru.
4. St. George’s Hospital, London SW17 0QT, UK.
5. Johns Hopkins University, Baltimore, MD 21205, USA.
6. Istituto Superiore di Sanità, Rome 00161, Italy.