Prevalence of West Nile Virus in Children Being Evaluated for Lyme Disease

Background: West Nile virus (WNV) is a flavivirus typically transmitted between mosquitoes and birds with occasional spill-over into other animals, including humans. Children evaluated for suspected Lyme disease may share environmental risk factors for WNV and present with overlapping symptoms. Our goal was to determine the prevalence of WNV infection in children with suspected Lyme disease. Methods: We performed a nested case-control study within a prospective cohort study of children with suspected Lyme disease aged 1–21 years enrolled at 1 of 8 Pedi Lyme Net emergency departments. Lyme disease was defined by either an erythema migrans (EM) lesion or positive two-tier serology. Cases with Lyme disease ( n = 305) were matched by age, symptoms, and enrolling center to symptomatic controls without Lyme disease ( n = 295). We performed indirect (Luminex microbead immunoassay MIA] with reflex IgM enzyme immunoassay [EIA]) and direct (polymerase chain reaction [PCR]) WNV testing. Acute WNV infection was defined with either a positive MIA and EIA or a positive PCR test result. Results: Of the 600 included patients, 15 (2.5%) had a positive and 53 (8.8%) had an equivocal WNV MIA result. Of these, only 1 had a positive EIA result. Another child had a positive WNV PCR test. The two children with active WNV infections also had acute Lyme disease (0.3%, 95% confidence interval 0.1%, 1.2%) with neurological symptoms. Conclusion: Acute WNV infection is uncommon in pediatric patients being evaluated for suspected Lyme disease. Routine WNV testing is not indicated when evaluating for suspected Lyme disease.