Resurgence of pertussis infections in Shandong, China: Space-time cluster and trend analysis

Abstract

Although vaccination is effective in preventing infection, pertussis remains endemic worldwide, including China. To lead better targeted prevention strategies, we examined dynamics of spatial and temporal patterns of pertussis transmission in Shandong, China, from 2009 to 2017. We used space-time cluster analysis, logistic regression analysis, and regression tree model to detect the changes in spatial patterns of pertussis infections in Shandong Province, China, between periods (2009-2011, 2012-2014, and 2015-2017). The yearly pertussis incidence rates dramatically increased by 16.8 times from 2009 to 2017. Shifting patterns of peaks of pertussis infections were observed over both time (from June-July to August-September) and space (from Linyi to Jinan), with increasing RR from 4.1 (95% CI: 2.3-7.4) (2009-2011) to 6.1 (95% CI: 5.6-6.7) (2015-2017) and obvious coincidence of peak time. West Shandong had larger odds of increased infections over the study period (odds ratio: 1.52 [95% CI: 1.05-2.17]), and pertussis had larger odds of spreading to east (odds ratio: 2.32 [95% CI: 1.63-3.31]) and north (odds ratio: 1.69 [95% CI: 1.06-2.99]) over time. Regression tree model indicated that the mean difference in yearly average pertussis incidence between 2009-2011 and 2015-2017 increased by more than 4-fold when the longitudes of counties are < 118.0°E. The geographic expansion of pertussis infection may increase the risk of epidemic peaks, coinciding with increased infections in the future. The findings might offer evidence for targeting preventive measures to the areas most in need to minimize the impact of the disease.