Endemic La Crosse Virus Neuroinvasive Disease in North Carolina Residents: 2000–2020

La Crosse virus neuroinvasive disease (LACVND) is the most common cause of arboviral encephalitis in children within the United States; in North Carolina, it is the most prevalent endemic mosquito-borne disease in humans. Here we report a surveillance summary of confirmed and probable LACVND during 2000–2020 using North Carolina Electronic Disease Surveillance System data, and we describe associated demographic characteristics, spatiotemporal distribution, clinical features, and mortality rates. A total of 355 cases (74.9% confirmed) were reported from 41 North Carolina counties; most cases (92%) occurred in 19 Western North Carolina counties. An average of 17 cases were reported annually with the majority (94%) of cases occurring between mid-June and early October (epiweeks 25–41). The median case age was nine years (range: 1–95 years), 79% were aged ≤ 18 years, and 56.6% were male. Cases commonly presented with headache (95.4%), fever (95.1%), and altered mental status (80.8%); encephalitis (82.0%) and meningitis (45.9%) were frequently diagnosed. Encephalitis was more common in children (87%) than adults (62%) (P < .001). Similarly, seizures were more common in children (54%) than adults (27%) (P < .01). The case fatality rate was 1.4%; however, differences in age-specific rates were observed. Changes in case definitions and reporting requirements, missing data, different reporting sources, and the retrospective nature of this study are all important limitations of our study. Given the persistent endemicity of La Crosse virus in Western North Carolina, clinicians and public health providers should consider La Crosse virus disease in all individuals, especially children, with compatible symptoms and a travel history to endemic counties. Prevention measures and educational outreach/public health messaging should focus on caregivers and children in Western North Carolina counties and during times when transmission risk is higher (i.e., summer and early fall).