Infectious disease surveillance for generating early warnings to enable a prompt response during mass gatherings has long been a challenge in India as well as in other parts of the world. Ujjain, Madhya Pradesh in Central India hosted one of the largest religious festival in the world called âSimhasth kumbh melaâ on the banks of River Kshipra, where more than 50 million attendees came for holy dip during April 22 to May 21, 2016. The attendees included pilgrims (residents and visitors), observers, officials and volunteers.