Interesting study from 2014 about the impact of mass gatherings on an influenza pandemic, commissioned by the Department of Health and produced by Public Health England: The observational studies and the quasi-experimental study together provided evidence that mass gatherings are associated with a risk of influenza transmission, particularly within the specialised setting of Hajj. New evidence supports the findings that respiratory viruses (including influenza) are transmitted at specialised events such as the Hajj; however specific evidence for pandemic influenza does not suggest widespread transmission occurs. Four strands of evidence emerged from the outbreak reports.