( CNN ) -- Tuesday marked the last day of the Hajj , the annual pilgrimage that sees over two million Muslim pilgrims journey to Mecca in Saudi Arabia . It is one of the most celebrated events in the Islamic calendar , and one of the world 's largest public gatherings . Handling a crowd of that magnitude has n't always been easy , especially in light of public health worries and ISIS fears . To ensure such a feat goes off with minimal disruption , Saudi Arabia 's authorities have had to go high-tech . The crowd . Any event that draws crowds a million strong faces the risk of stampedes . Hajj pilgrims have not always been exempt from such a fate . The worst incident occurred in 1990 , when 1,426 pilgrims were trampled to death . A similar event took place in 2006 , when 363 people lost their lives . Since then , the Saudi government has used live crowd analytics software CrowdVision to manage the throng . `` It spots patterns of crowd behavior that indicate potential danger such as high densities , pressure , turbulence , stop-and-go waves and other anomalies , '' Fiona Sterns , CrowdVision 's co-founder , told the BBC . Back in a central control room , police and military personnel monitor the live data feeds provided by the software , which lets them see in real-time where the crowds are thickest . The traffic . Transporting two million people at once has the potential of setting new records in gridlock . To combat this , authorities employ 15,000 public buses to help move the masses between the holy sites . Like the crowds , the buses ' movements are also tracked by wireless monitors to help authorities grasp where traffic jams hold up the procession , and make adjustments accordingly . The government has also invested in several long-term public transport initiatives to take some pressure off the roads . The Al Mashaaer Al Mugaddassah Metro was completed in 2011 , and ferries pilgrims between Mecca , Mount Arafat , Muzdalifah and Mina -- all required stops on the Hajj . The railway line was designed to shuttle 72,000 passengers an hour . Construction has also begun on a four-line metro system for the city of Mecca . Public health . While various health crises -- namely MERS and Ebola -- have cast a shadow over this year 's proceedings , organizers employed a medical army to address any health issues that might arise . According to the World Health Organization ( WHO ) , this year there were 180 ambulances on standby , as well as 22,000 health care professionals , 141 health centers , 25 hospitals with 5,250 beds , and 19,000 units of varying blood types . Officials also banned pilgrims from Ebola hot zones -- namely Guinea , Liberia and Sierra Leone . `` WHO has been closely coordinating with the Ministry of Health of Saudi Arabia to ensure that preparedness measures are in place , '' says Rana Sidani , a WHO spokesperson . The security . The rise of ISIS and other Islamic extremist groups in the region put added pressure on Saudi Arabia this year to increase security measures during the Hajj . `` I would not put it past ISIS to try to disrupt the Hajj and I think Saudi authorities are well aware of that possibility , '' said Fahad Nazer , a terrorism analyst at JTG Inc and a former political analyst at the Saudi embassy in Washington , told The National . To safeguard against the possibility of attack , officials installed thousands of CCTV cameras throughout the country , focusing on the holy sites , and employed facial recognition technology . They also employed 60,000 security troops . `` These forces will be stationed in Mina , Arafat and Muzdalifah to ensure the safety of pilgrims and enable them to perform their rites with ease and comfort , '' Major General Osman Al Mahraj , director of general security , told the Saudi Gazette .
Tuesday marked the last day of the Hajj , the annual pilgrimage that draws over two million Muslim pilgrims . This year there were 180 ambulances , 22,000 health care professionals and 19,000 units of blood on standby . Score: 6