The_analysis_of_persistent_typhoid_in_Chile

Up until 1991, typhoid fever was very common in Santiago, Chile. The hyper-endemicity of typhoid was eventually brought under control using a combination of vaccination of schoolchildren with Ty21a live oral vaccine, identification and treatment of epidemiologically-relevant chronic carriers and prohibition of the use of untreated sewage to irrigate salad vegetable crops. Since 1991, amplified transmission was stopped and the incidence of typhoid plummeted. Since 2005 cases of typhoid have been very uncommon. Ongoing studies are exploring whether these rare cases in Santiago are the consequence of short-cycle spread of indigenous strains from elderly chronic carriers (originally infected in Santiago in the 1970s and 1980s) or are due to importations from travellers and immigrants from other Latin American countries where typhoid is more endemic. The first tranche of Salmonella Typhi DNA samples in this study represent isolates from children and adults and with acute typhoid fever, adult chronic carriers, and the environment, all from the 1980s. A second separate smaller tranche of specimens includes DNA from more recent cases (since 2010) and from recently identified chronic carriers.