Abstract
BackgroundBrucellosis is a serious public health problem primarily affecting livestock workers. The strong seasonality of the disease indicates that climatic factors may play important roles in the transmission of the disease. However, the associations between climatic variability and human brucellosis are still poorly understood.MethodsData for a 14-year series of human brucellosis cases and seven climatic factors were collected in Yulin City from 2005 to 2018, one of the most endemic areas in northern China. Using cross-correlation analysis, the Granger causality test, and a distributed lag non-linear model (DLNM), we assessed the quantitative relationships and exposure-lag-response effects between monthly climatic factors and human brucellosis.ResultsA total of 7103 cases of human brucellosis were reported from 2005 to 2018 in Yulin City with a distinct peak between April and July each year. Seasonal fluctuations in the transmission of human brucellosis were significantly affected by temperature, sunshine duration, and evaporation. The effects of climatic factors were non-linear over the 6-month period, and higher values of these factors usually increased disease incidence. The maximum separate relative risk (RR) was 1.36 (95% confidence interval [CI], 1.03–1.81) at a temperature of 17.4 °C, 1.12 (95% CI, 1.03–1.22) with 311 h of sunshine, and 1.18 (95% CI, 0.94–1.48) with 314 mm of evaporation. In addition, the effects of these three climatic factors were cumulative, with the highest RRs of 2.27 (95% CI, 1.09–4.57), 1.54 (95% CI, 1.10–2.18), and 1.27 (95% CI, 0.73–2.14), respectively.ConclusionsIn Yulin, northern China, variations in climatic factors, especially temperature, sunshine duration, and evaporation, contributed significantly to seasonal fluctuations of human brucellosis within 6 months. The key determinants of brucellosis transmission and the identified complex associations are useful references for developing strategies to reduce the disease burden.
Highlights
Brucellosis is a serious public health problem primarily affecting livestock workers
Temporal trend and seasonality of human brucellosis and climatic factors In the period from 2005 to 2018, a total of 7103 cases of human brucellosis were reported in the study area
The cross-correlation analysis revealed that five climatic factors—temperature, precipitation, evaporation, sunshine duration, and wind velocity—were positively correlated with the human brucellosis incidence, and relative humidity and atmospheric
Summary
Brucellosis is a serious public health problem primarily affecting livestock workers. Human infections occur mainly through contact with infected livestock or aborted materials or consumption of unpasteurized food contaminated with Brucella spp., especially raw milk and other products from goat and sheep [4, 5]. People of all ages and both sexes can be affected by the disease, and the occupational groups at higher risk of infection are shepherds, slaughterhouse workers, animal breeders, and veterinarians [3]. Given that Brucella spp. infections occur via various routes of diverse animal reservoirs and transmissions as well as the lack of effective vaccines and timely treatment, the rates of initial treatment failure and relapse along with the degree of substantial residual disability are high [6, 7]
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