This year’s hajj pilgrimage is well-underway, with hundreds of thousands of muslims gathering in Mecca. The journey to Mecca is a requirement of all able-bodied muslims at least once in their lifetime. It attracts around three million people from across the world. But the concentration of so many people from different backgrounds and countries has often caused problems. In the past, the hajj has been hit by hotel fires, political protests, stampedes and deaths. This year there’s a new worry: swine flu.Saudi health officials have made careful preparations, including detection devices at ports and airports to screen arrivals, and improved facilities at hospitals. They are concerned that the virus could spread rapidly among the pilgrims, who will then return home sick, sparking a global resurgence of the flu. And, casting a further dampener on proceedings, heavy rain has hit Mecca, leaving many roads under water.