Implementing the Health Early Warning System based on syndromic and event-based surveillance at the 2019 HajjKingsley Lezor Bieh, Anas Khan, Saber Yezli, Ahmed El-Ganainy, Sari Asiri, Badriah Alotaibi, Sujoud Ghallab, Amgad Elkholy, Abdinasir Abubakar and Hani Jokhdar