Brown Marusiak Amanda, Giandomenico Dana A, Hollingsworth Brandon D, Mokashi Neha V, Delamater Paul L, Reiskind Michael, Barbarin Alexis M, Williams Carl, Boyce Ross M
Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America.
Institute for Global Health and Infectious Diseases, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America.
PLoS Negl Trop Dis. 2025 Aug 13;19(8):e0013406. doi: 10.1371/journal.pntd.0013406. eCollection 2025 Aug.
North Carolina (NC) ranks among the top five states for spotted fever rickettsiosis (SFR) cases and second for ehrlichiosis in the U.S. Identifying geographic clusters of cases is important to elucidate disease risk and inform public health response, including resource allocation. This study examined geographic patterns of tick-borne disease incidence in NC over a 10-year period and modeled predictors of disease severity.
METHODOLOGY/FINDINGS: We analyzed 6,748 SFR and 1,216 ehrlichiosis cases reported to the NC Electronic Disease Surveillance System between January 2010 and December 2019. Average annual incidence was evaluated in two-year periods using global spatial autocorrelation (Moran's I) and Local Indicator of Spatial Association. We found that ehrlichiosis clusters were detected in north and central NC as well as the coastal Tidewater region, with consistently high incidence in these areas. SFR clustering occurred in similar areas, with high and increasing incidence statewide. Severe cases of ehrlichiosis followed a similar pattern, while severe SFR clusters were distributed more broadly across the state. Additionally, Black/African-American individuals made up a greater proportion of both severe ehrlichiosis and SFR cases relative to non-severe cases. Regression models showed that known tick exposures were associated with lower odds of severe SFR. For SFR, treatment delays of 1-7 days were linked to severity, but delays >7 days were not. In contrast, delays >7 days for ehrlichiosis were associated with lower odds of severe disease.
CONCLUSIONS/SIGNIFICANCE: Associations found here between severity and treatment delay may reflect care-seeking behaviors, testing practices, and background seroprevalence. Geographic differences in disease incidence and severity warrant further investigation and future surveillance. Public health interventions should focus on the north-central and Tidewater regions, focusing on exposure risks awareness for outdoor activities and checking for ticks, which could impact treatment timing and ultimately reduce severity.
在斑疹热立克次体病（SFR）病例方面，北卡罗来纳州（NC）在美国排名前五，在埃立克体病方面排名第二。识别病例的地理聚集对于阐明疾病风险并为公共卫生应对（包括资源分配）提供信息很重要。本研究调查了北卡罗来纳州10年间蜱传疾病发病率的地理模式，并对疾病严重程度的预测因素进行了建模。
方法/发现：我们分析了2010年1月至2019年12月期间向北卡罗来纳州电子疾病监测系统报告的6748例SFR病例和1216例埃立克体病病例。使用全局空间自相关（莫兰指数I）和空间关联局部指标在两年期内评估年平均发病率。我们发现，在北卡罗来纳州北部、中部以及沿海的潮水区域检测到埃立克体病聚集，这些地区的发病率持续较高。SFR聚集发生在类似地区，全州发病率高且呈上升趋势。严重的埃立克体病病例呈现类似模式，而严重的SFR聚集在全州分布更广泛。此外，相对于非严重病例，黑人/非裔美国人在严重的埃立克体病和SFR病例中所占比例更大。回归模型显示，已知的蜱暴露与严重SFR的较低几率相关。对于SFR，1 - 7天的治疗延迟与疾病严重程度有关，但延迟超过7天则无关。相比之下，埃立克体病延迟超过7天与严重疾病的较低几率相关。
结论/意义：此处发现的严重程度与治疗延迟之间的关联可能反映了就医行为、检测实践和背景血清阳性率。疾病发病率和严重程度的地理差异值得进一步调查和未来监测。公共卫生干预应集中在中北部和潮水区域，重点是提高对户外活动暴露风险的认识以及检查蜱虫，这可能会影响治疗时机并最终降低严重程度。
