Procedures for obtaining informed consent have been developed in accordance with the Ottawa Statement on the Ethical Design and Conduct of Cluster Randomized Trials . Gatekeepers have been defined as the health care professional in charge of the HC and village chiefs and their deputies. Village chiefs will be asked to provide written permission for the randomization of their village. It will not be possible to obtain individual-level informed consent for participation, as each arm will likely include several thousand individuals during an emergency. We have met established criteria for the waiver of individual consent in a cluster-randomized trial [28, 29]. Nonetheless, in villages receiving household chemoprophylaxis, the study nurse will present the risks and benefits of taking ciprofloxacin to household members, and it will be administered only to those who are willing. In the village-wide prophylaxis arm, a series of community meetings will be held in advance of the mass distribution, during which the study and its risks and benefits will be presented and questions may be answered. Those persons who present to the ciprofloxacin distribution site will be considered to have been duly informed of the risks and benefits of taking ciprofloxacin and the voluntary nature of their participation.