Concurrently, specimens of brain tissue from three human encephalitis cases, forwarded by the New York State Department of Health to the University of California, Irvine, were reported as positive for West Nile-like virus sequence by genomic analysis. In other tests at CDC, flavivirus antigen was detected in one of the autopsy specimens by immunohistochemistry, and a West Nile-like virus genomic sequence identical to that derived from the bird isolates was observed in a human brain specimen from an encephalitis case. Testing at CDC on September 23 by polymerase chain reaction (PCR) and DNA sequencing of these isolates indicated that they were closely related to West Nile virus (WNV), which has never been isolated in the western hemisphere. NVSL isolated viruses from the birds' tissues and forwarded them to CDC on September 20 for identification and characterization. Department of Agriculture National Veterinary Services Laboratories (NVSL) in Ames, Iowa, on September 10 to be tested for common avian pathogens and the equine encephalitis viruses all tests were negative. Tissue specimens from these birds and a crow with pathologic evidence of encephalitis from New York state were sent to the U.S. Necropsies performed on these birds at the zoo revealed varying degrees of meningo-encephalitis and severe myocarditis. During September 7-9, officials of the Bronx Zoo noted the deaths of a cormorant, two captive-bred Chilean flamingoes, and an Asian pheasant. A clinical case is defined as a presumptive diagnosis of viral encephalitis with or without muscle weakness or acute flaccid paralysis, Guillain-Barre syndrome, aseptic meningitis, or presence of the clinical syndrome characterizing the initial cluster of cases in a patient presenting after August 1.īefore and concurrent with this outbreak, local health officials observed increased fatalities among New York City birds, especially crows. Surveillance is also ongoing in surrounding areas. To define the geographic extent of the outbreak, NYCDOH initiated active surveillance on August 30, and the Westchester County Department of Health and the Nassau County Department of Health initiated active surveillance on September 3. On the basis of these findings, aerial and ground applications of mosquito adulticides and larvacides were instituted in northern Queens and South Bronx on September 3. Eight of the earliest case-patients were residents of a 2-by-2-mile area in northern Queens. Testing of these initial cases by IgM-capture ELISA for antibodies to the common North American arboviruses was positive for SLE virus on September 3 at CDC. On investigation, NYCDOH initially identified a cluster of six patients with encephalitis, five of whom had profound muscle weakness (with axonal neuropathy by electromyelogram and requiring respiratory support ). On August 23, 1999, an infectious disease physician from a hospital in northern Queens contacted the New York City Department of Health (NYCDOH) to report two patients with encephalitis. Louis encephalitis (SLE) virus based on positive serologic findings in cerebrospinal fluid (CSF) and serum samples using a virus-specific IgM-capture enzyme-linked immunosorbent assay (ELISA), the cause of the outbreak has been confirmed as a West Nile-like virus based on the identification of virus in human, avian, and mosquito samples. Outbreak of West Nile-Like Viral Encephalitis - New York, 1999Īn outbreak of arboviral encephalitis was first recognized in New York City in late August and has since been identified in neighboring counties in New York state. For assistance, please send e-mail to: Type 508 Accommodation and the title of the report in the subject line of e-mail. Persons using assistive technology might not be able to fully access information in this file.
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