The long-term goal of this study is to more precisely define the role of mass azithromycin treatments as an intervention for reducing childhood morbidity and increasing growth, and for the potential selection of antibiotic resistance. The investigators propose a set of 3 cluster-randomized trials comparing communities randomized to oral azithromycin with those randomized to placebo. To assess the generalizability of the intervention, investigators will monitor for antibiotic resistance, which could potentially limit adoption of mass antibiotic treatments. The investigators will also assess several measures of infectious diseases. The investigators hypothesize that mass azithromycin treatments will reduce childhood morbidity and will be accompanied by an acceptable level of antibiotic resistance.