1. Unit of Infectious Diseases, Department of Internal Medicine, Ospedale Civile "Spirito Santo," Pescara, Italy.
2. Section of Epidemiology and Public Health, University "G. d'Annunzio" of Chieti, Italy.
3. Department of Oncological Science, Mount Sinai School of Medicine, New York, New York.
4. Cornell University Medical College, New York, New York.