Spatiotemporal Evolution of Lyme Disease in North Carolina from 2010 to 2020

Lyme disease is the most common vector-borne disease in the United States with a majority of cases occurring in the Northeast, upper Midwest, and mid-Atlantic. While historically a low incidence state, North Carolina (NC) has seen substantial increases in reported Lyme disease cases over the past decade. The aim of this study was to characterize the spatiotemporal evolution of Lyme disease in NC from 2010 to 2020. Confirmed and probable cases reported to the NC Division of Public Health were included in the analysis. Cases with a documented travel history to a high transmission area during a defined period of interest were excluded. The study period was divided into 4 subperiods: 2010–2012, 2013–¬2015, 2016–2018, and 2019–2020. Data were aggregated by zip code of residence of the identified case. Absolute change in incidence per 100,000 from 2010–2012 to 2019–2020 was mapped to identify zip codes with the largest changes. Global and local spatial autocorrelation analyses were performed to evaluate the overall distribution of cases and identify high incidence zip codes with high incidence neighboring zip codes (i.e., hotspot areas) for each subperiod. Overall, we found the largest absolute changes in incidence, up to zero to 464.7 cases per 100,000 people in zip codes located in Ashe County, in the northwestern part of the state and extending towards Buncombe County. The distribution of cases became increasingly and significantly clustered over the study period, from a Moran’s I of 0.012 (p = 0.127) in 2010–2012 to a Moran’s I of 0.403 (p < 0.001) in 2019–2020. Hotspots included 22 high incidence zip codes in the 2019–2020 subperiod in the northwestern part of the state, largely co-located with areas experiencing the largest absolute changes in incidence. The results demonstrate the rapid emergence of Lyme disease in northwestern NC over the past decade. Efforts targeted to these geographic areas are urgently needed to educate local residents, medical providers, and public health officials in order to prevent and ultimately reduce the burden of Lyme disease.