On the other hand, given the growing problem of antibiotic resistance, even if this trial were to show overwhelmingly positive results, it would be impossible to recommend chemoprophylaxis as a routine epidemic response without having evidence on the possible effect of mass distributions of ciprofloxacin on the prevalence of resistant pathogens. We believe that by carrying out the sub-study during the epidemic we will provide the most realistic evidence on which to base potential decision making.