A system consisting of one UV-A (365 nm) and two UV-C (265 nm) light-emitting diodes (LEDs) was built to evaluate the effect of single and combined exposures to UV-A and UV-C LEDs on Klebsiella pneumoniae and Escherichia coli inactivation and subsequent reactivation. The dose was measured by actinometry using potassium ferrioxalate. Of laboratory prepared samples, 10 mL were irradiated for 20, 30, 45, 60 and 90 s. Logarithmic inactivation and percentages of photoreactivation and dark repair were calculated. E. coli and K. pneumoniae were reduced by more than 7 and 4 logs, respectively, at a dose of 21.5 mJ cm−2 using UV-C. No positive synergistic effect on the inactivation of the two bacteria was observed when using a simultaneous combination of UV-C and UV-A, probably due to a reactivation of the bacteria in the presence of UV-A light, which was not observed in irradiated samples under an individual exposure of 265 nm. For E. coli under 265 nm, the percentage of photoreactivation amounted to 10%, 3 h after irradiation. The results of this study demonstrated the capacity to inactivate E. coli and K. pneumoniae up to a considerable level and provide information for the application of UV LEDs in point-of-use systems.

OBJECTIVE: To analyze factors associated with diarrheal disease in the rural Caribbean region of Colombia. METHOD: A cross-sectional study conducted in the rural area of the Cesar Department, Colombia, between November 2017 and June 2018. Self-reported cases of diarrheal disease were surveyed, and water samples from 42 households were collected and analyzed. Descriptive statistics were employed in the analysis of socioeconomic status, environmental and sanitary conditions, and we evaluated their association with the diarrheal disease using the Poisson regression models. Each model was adjusted with variables suggested by specific directed acyclic graphs. RESULTS: Poor water supply conditions, hygiene and basic sanitation were reported in the study area. All water samples were classified either as high risk for health problems or unfit for human consumption. The diarrheal disease had a prevalence of 7.5% across all ages and of 23.5% in children under five years old. The variables rainy season (PR = 0.24; 95%CI 0.07–0.85), children under five years old (PR = 4.05; 95%CI 1.70–9.68), water from deep wells (PR = 16.90; 95%CI 2.45–116.67), water from artificial ponds (PR = 11.47; 95%CI 1.27–103.29), toilets availability (PRA = 0.23; 95%CI 0.06–0.96), and swine presence (PR = 0.20; 95%CI 0.05–0.74) were significantly associated with the occurrence of diarrheal disease. CONCLUSION: Water supply, hygiene and basic sanitation conditions have been associated with the diarrheal disease, affecting almost a quarter of the population under five years old. There is an urge for the design of effective policies that improve environmental and sanitation conditions in rural areas.

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