1 Division of General Internal Medicine, Department of Medicine, Tokyo Joto Hospital, Japan Community Health Care Organization, 1360071 Tokyo, Japan.
2 Emerging and Re-Emerging Infectious Diseases Unit, National Institute for Infectious Diseases "Lazzaro Spallanzani," Via Portuense, 292, 00149 Rome, Italy.
3 Muribushi Project for Teaching Hospitals, 9012132 Okinawa, Japan.