Abstract
.From 1975 to 1983, a large epidemic of typhoid fever (TF) affected the metropolitan region (MR) of Chile (incidence rate [IR] of 219.6 per 105 in 1983). In 1983–1984, interventions were implemented focusing on person-to-person transmission (vaccination, food handlers’ control, and mass communication) and regulations to control irrigation waters containing fecal contaminates. In 1991, a second intervention was quickly implemented to avoid the cholera epidemic affecting neighboring countries (total prohibition of growing or selling crops in the MR). We explored the potential impact of these interventions on the epidemic. We created a yearly database of the MR TF cases, population, and contextual factors of TF from 1969 to 2012. We first analyzed the epidemic (Joinpoint regression), identified predictors of TF (Poisson multiple regression), and then analyzed the effect of the interventions (interrupted time series model). The main predictor of the TF epidemic was the rate of unemployment. In relation to the 1983–1984 person-to-person interventions, TF came down by 51% (95% confidence interval [CI]: 30.2–65.0%) and continued to decrease at a rate of 10.4% (95% CI: 5.8–15.6%) per year until 1991. In 1991, with the strong environmental control of the sewage-irrigated crops, TF further decreased by 77% (95% CI: 69.0–83.1%) and continued decreasing thereafter at 13% (95% CI: 11.3–15.6%) per year until the end of the study period. Today, 40 years after the epidemic, TF is a rare disease in the MR of Chile.
Highlights
From 1950 to 1976, typhoid fever (TF) was highly endemic in Chile and did not seem to respond to improvements in household coverage of safe drinking water or sewage collection; in 1977, a large epidemic cycle began (Supplemental Figure 1).[1]
The TF epidemic was attributed to various causes, including person-to-person transmission of Salmonella enterica serovar Typhi (ST), the short cycle associated with poor personal hygiene,[4] and deterioration of safe food handling practices,[2] deterioration of drinking water chlorination,[6,7] or the use of untreated sewage in irrigation systems.[8,9]
Typhoid fever incidence had a strong downward trend until 1991 and in 1992, its decline accelerated reaching, by the end of the study period, the lowest TF incidence rates (IRs) reported in the metropolitan region (MR) (Figure 1)
Summary
From 1950 to 1976, typhoid fever (TF) was highly endemic in Chile and did not seem to respond to improvements in household coverage of safe drinking water or sewage collection; in 1977, a large epidemic cycle began (Supplemental Figure 1).[1] This has been the largest TF epidemic reported in Latin America, occurring in a country with the best health indicators in the region.[2,3] The highest incidence rates (IRs) were seen in the metropolitan region (MR), one of Chile’s 16 geographical regions, located in the center of the country. We collected all available data and used sound statistical analysis, to evaluate this association, which could inform policy makers in areas of high TF incidence
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