Randomization of Treatment Allocation. In each site, 30 communities within a contiguous area of 300,000 to 600,000 individuals will be randomized into the azithromycin or placebo arm. The investigators will use a simple random sample separately for each study site, but without stratification or block randomization within the site. These communities are being randomized from the same pool of communities eligible for a sister trial (Mortality Reduction After Oral Azithromycin (MORDOR) - Morbidity Study).