Illustration of transformation of age specific MERS-CoV incidence in the general population of the Makkah region to incidence in foreign pilgrims to the Hajj.

Here we show the population of Makkah, MERS cases occurring in the first 27 weeks of 2014, expected number of foreign pilgrims, and expected number of cases in foreign pilgrims. Hajj pilgrims are at risk for two weeks; hence, for each age category, C, the expected incidence in Hajj pilgrims (without onward transmission) is (cases in C)/(population in C × 27 weeks) × (foreign pilgrims in C × 2 weeks).