Vanhu vari pakati pemamiriyoni 17 kusvika ku25 vane utachiona hwechirwere cheriver blindness, uye vanenge mamiriyoni 0.8 havachanyatsooni zvakanaka. Utachiona uhwu hunonyanya kutapukira munyika dzesub-Saharan Africa, kunyange zvazvo pane vamwe vakatapukirwa kuYemen nenzvimbo dzakataramuka dzeCentral neSouth America. Muna 1915, chiremba anonzi Rodolfo Robles ndiye akatanga kuona kuti hwemusi iri ndiro rinoparira chirwere chemaziso. World Health Organization yakanyora pasi chirwere ichi sechirwere chakashayirwa hanya chekunzvimbo dzinopisa.