The infection is passed from one child to another when they have infected eye and nose secretions (dirty faces) which easily spread. Unlike other infectious diseases, for trachoma a single episode of infection is often not uncomfortable or noticed as being different. The problem is that repeated infections keep the inflammation present. The longer the inflammation goes on the more discomfort and severe the scarring, and the more severe the scarring the greater the risk of blindness.
A child easily may have between 30-40 episodes of reinfection during childhood and they may have had 160-180 infections to have scarring severe enough to cause blindness in later life(4). Each episode of infection may last a few months, but repeated reinfection leads to the appearance of continuing infection and disease.
(4) Gambhir M, Basanez MG, Burton MJ, Solomon AW, Bailey RL, Holland MJ, et al. The development of an age-structured model for trachoma transmission dynamics, pathogenesis and control. PLoS Negl Trop Dis. 2009;3(6):e462 doi: 10.1371/journal.pntd.0000462 [PMC free article] [PubMed]
