Orange-crowned Warblers readily succumbed to WNV, but not SLEV, experimental infection, and in agreement 11% of Orange-crowned Warblers found dead were WNV positive, whereas no live birds tested positive for WNV antibody. Proof of principal for long distance movement was shown recently in the Old World from the recovery of WNV from migrating storks5 and WNV antibody from additional migrant varieties.6,7 Historically in the United States, large studies along the Mississippi and Atlantic flyways failed to document the introduction of encephalitis viruses by northbound migrants.8C11 In agreement, genetic studies have shown marked separation between North and South American strains of arboviruses, such as eastern equine encephalomyelitis (EEEV),12 western equine encephalomyelitis (WEEV),13,14 and St. Louis encephalitis (SLEV)15,16 viruses, suggesting limited genetic exchange. Temporal studies in California have shown intermittent genotype modify among WEEV and SLEV isolates, 17C19 indicating possible intro and alternative events. Neotropical migratory parrots would seem to become the likely transport mechanism for such introductions. The north shore of the Salton Sea in Coachella Valley is definitely a unique area to study the introduction of arboviruses into western North America by northbound migrants. Typically, this is the 1st location in California and generally the western United States, where arboviral infections are found out Tmem178 in mosquitoes each year,19C21 and the Imperial Valley just south of this location is definitely where WNV was first discovered west of the continental divide.22 Large numbers of neotropical migrants transiting the Pacific flyway use marshes in the north shore like a stopover site after traversing the Salton Sea and adjacent desert facilitating capture. In addition, arboviruses are active enzootically during most summers at wetlands surrounding the Salton Sea, indicating amplification after local overwintering or intro. From 1996 through 2007, we sampled both migratory and resident birds for the presence of antibody or viral illness in the north shore of the Salton Sea each spring to test the hypothesis that northbound migrants repeatedly introduce arboviruses into California. Related data concurrently collected in Kern Region in the southern end of the Central Valley offered an interesting assessment and a slightly different faunal composition. To assist in the interpretation of our field serology data, we experimentally infected Orange-crowned Warblers ( 0.05) Podophyllotoxin than the percentage EIA positive for the spring migrants. Of these, 5 and 3 from 642 Common Yellowthroat, 0 and 3 from 42 Black-headed Grosbeak, and 0 and 1 from 182 Bullock’s oriole sera were positive for WEEV or flavivirus antibodies, respectively; all other species outlined in Table 1 Podophyllotoxin tested bad. Only the 3 Black-headed Grosbeak sera were confirmed by PRNT to be SLEV antibody positive. In contrast, 2,987 (5.3%) sera from 56,174 parrots collected over the entire study were positive for arboviral antibodies (Table 1), an order of magnitude greater than spring neotropical migrants. These non-neotropical migrant parrots included winter, summer season, and year-round Podophyllotoxin occupants, which were likely revealed locally to arboviruses. Table 1 Neotropical migratory bird species collected in Coachella Valley (COAV) and Kern Region (KERN) during spring (AprilCJune) and tested for antibody against arboviruses* Coquillett) was related directly to the bimodal pattern of mosquito large quantity at marshes along the Salton Sea. Disease amplification continued into June and the numbers of positive swimming pools recognized was highest during summer season, reducing in September as the migrants appeared again on their southbound airline flight..