1. From the King Faisal Specialist Hospital & Research Centre, Riyadh, Saudi Arabia
2. Correspondence: Sami Al Hajjar · Head, Pediatric Infectious Diseases, Department of Pediatrics, King Faisal Specialist Hospital & Research Centre, PO Box 3354, Riyadh 11211 Saudi Arabia · T: +966 1 4647272 F: +9661 4427784 · hajjar@kfshrc.edu.sa
3. From the Harvard Medical School, Boston, Massachusetts, USA