1. Department of Hygiene, Epidemiology and Medical Statistics, Medical School, University of Athens, Athens, Greece.
2. Antiviral Research, Abbott Global Pharmaceutical R&D, Abbott Park, Illinois.
3. Red Cross General Hospital, Athens, Greece.
4. Clinical and Epidemiological Virology, Rega Institute for Medical Research, Katholieke Universiteit Leuven, Leuven, Belgium.
5. Centro Hospitalar de Lisboa Ocidental, Lisbon, Portugal.
6. Instituto de Higiene e Medicina Tropical, Universidade Nova de Lisboa, Lisbon, Portugal.