1. Red Cross Blood Bank Foundation, Willemstad, Curaçao, The Netherlands Antilles.
2. Stichting HIV Monitoring (SHM), Amsterdam, The Netherlands.
3. St Elisabeth Hospital, Willemstad, Curaçao, The Netherlands Antilles.
4. Epidemiology and Research Unit, Medical and Public Health Service of Curaçao, Willemstad, Curaçao, The Netherlands Antilles.
5. Department of Infectious Disease Epidemiology, Medical Faculty of Imperial College, London, United Kingdom.