At the end of next month Saudi Arabia will again host the Hajj—the largest annual gathering in the world—which attracts more than two million pilgrims from almost every country on earth.1 2 For the individual pilgrim this is a deeply spiritual journey that represents the culmination of months if not years of preparation. From a public health perspective, however, such a gathering makes the possible rampant spread of the influenza virus and a global pandemic—which many experts believe is overdue—a potentially devastating prospect that has been inadequately prepared for.3

Recent work highlighting the high rates of infection and carriage of influenza virus in pilgrims returning from Mecca has emphasised the need for internationally agreed strategies to minimise the risk of a pandemic.4 5 6 Such a strategy should centre on ways to prevent transmission, but must …