Hundreds of thousands of Muslims have poured into the holy city of Mecca for the annual hajj pilgrimage. The hajj is one of the five pillars of Islam and is mandatory once in a lifetime for all Muslims, provided they are physically fit enough and financially capable of performing it. This year the threat of the Middle East respiratory syndrome corona virus (MERS-CoV) has raised fear of an epidemic, prompting many pilgrims to don face masks as a precaution against infection. An estimated thirty eight people have died in Saudi arabia due to the virus.