Retrospective IgM ELISA testing of sera and CSF from patients with encephalitis or meningitis who were previously tested for SLEV were confirmed positive for WNV infection, even in those who previously had negative or equivocal SLEV results. Before 1999, WNV had never been detected in the Western Hemisphere. Finally, virus was isolated from Culex pipiens mosquitoes, providing evidence for the presumed vector for virus transmission. By October, 15 horses had developed encephalitis on Long Island in New York and were found to be positive for WNV. Crow deaths were then confirmed to be caused by WNV. Simultaneously, researchers isolated virus from brains of patients who died from encephalitis during the outbreak and identified a Kunjin/West Nile-like flavivirus based on sequencing, further confirming the etiology. Sequencing initially revealed a strain most likely related to WNV, initially referred to as WNV-like then later confirmed to be WNV lineage 1, most closely related to the 1998 Israel strain. Brain tissues from these birds were sent to the United States Department of Agriculture National Veterinary Services Laboratories (NVSL), with viral isolates then sent on to CDC for sequencing. Approximately 2 weeks after the launch of the investigation by NYCDOH, captive exotic birds at the Bronx Zoo began to die with encephalitis determined to be the cause of death as diagnosed by the zoo veterinary pathologist, Dr. While massive die-offs of American crows (family Corvidae) were initially thought to be linked to the human outbreak, the New York state pathobiologist reported that the deaths were related to mass poisonings. Louis encephalitis virus (SLEV) by monoclonal antibody capture-enzyme linked immunosorbent assay (MAC-ELISA) at CDC, leading to swift implementation of mosquito control measures. Initial testing of sera and cerebrospinal fluid (CSF) from a subset of suspect patients were found to be positive for IgM antibodies against St. Based on patient and family interviews and environmental inspections, it became apparent that the most likely pathogen was mosquito borne. Similar cases were also quickly identified at neighboring hospitals, and the NYCDOH requested assistance from the Centers for Disease Control and Prevention (CDC) to help identify the cause. Deborah Asnis) in the borough of Queens, prompting an investigation. In late August of 1999, 2 cases of encephalitis were reported to the New York City Department of Health and Mental Hygiene (NYCDOH) by an infectious disease physician (Dr. In the mid-1990s, a new strain of WNV (lineage 1) emerged that resulted in a high proportion of neurological infections, with epizootics occurring in Romania, other parts of Europe, Russia, and Israel. Infections were typically characterized as subclinical or causing mild febrile illness. West Nile virus (WNV) was first discovered in Uganda in 1937, and for more than 60 years, circulated in an enzootic mosquito-borne transmission cycle throughout Africa, the Middle East, Russia, and Europe, with the predominant strain being lineage 2. Introduction and history of West Nile virus in North America The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Ĭompeting interests: The authors have declared that no competing interests exist. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.įunding: The authors were funded in part by NIH/NIAID (U19AI089992-06)(K.O.M.), the Chao Foundation (K.O.M.), and the Brockman Foundation ( ) (K.O.M). Vasconcelos, Instituto Evandro Chagas, BRAZILĬopyright: © 2021 Ronca et al. Citation: Ronca SE, Ruff JC, Murray KO (2021) A 20-year historical review of West Nile virus since its initial emergence in North America: Has West Nile virus become a neglected tropical disease? PLoS Negl Trop Dis 15(5):Įditor: Pedro F.
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