A stool sample container will be distributed to each participant the day before sample collection, together with instructions for collecting the sample the following morning. Study staff will then return to the village to collect the fresh stool samples. The same procedures will be followed on days 7 and 28. In villages receiving ciprofloxacin prophylaxis, day 0 samples will be collected up to the time of ciprofloxacin administration in the village. At days 7 and 28, samples will also be accepted the day following the scheduled sample collection (i.e., days 8 and 29), if the participant is not able to provide a sample on the scheduled day.