Mass antimicrobial administrations have been remarkably successful in reducing the prevalence of the ocular strains of Chlamydia that cause trachoma. Repeated distributions progressively lower the prevalence of infection, and in some cases may even result in local elimination. Mass treatments cannot be continued forever, due to concerns about cost and antibiotic resistance. The hope has been that other measures such as latrine construction and hygiene programs would prevent infection from returning. Unfortunately, no non-antibiotic measure has yet demonstrated an effect on infection.