Hospital Infection Control Response To The Threat of a New Epidemic: West Nile Virus

R. Blair, N. Donegan, L. Bell, and D. Lucey. Washington Hospital Center, Washington, DC.

ISSUE: In response to reported cases of human West Nile virus (WNV) infection in the state of New York during 1999 and an anticipated spread throughout the eastern United States in 2000, a large hospital in Washington, DC developed a meningitis surveillance system (MSS). The MSS prospectively alerts Infection Control Practitioners (ICP) and Infectious Disease physicians (IDP) of suspicious encephalitis and aseptic meningitis cases. Prior to initiation of this system, meningitis and encephalitis cases were identified retrospectively and sporadically. PROJECT: Case-finding methods include the use of Centers for Disease Control and Prevention and IDP definitions. Inclusion criteria for cerebrospinal fluid (CSF) specimens are absolute white blood cell (WBC) counts greater than 9, and exclusion criteria are WBC differentials over 50% neutrophils or bloody specimens. CSF specimen reports are screened, categorized, and linked to a Microsoft ACCESS surveillance worksheet for immediate ICP case review. Suspect cases are expeditiously reported to the IDPs and the Public Health Department, allowing for appropriate follow-up and polymerase chain reaction (PCR) testing. A graph of aseptic meningitis occurrence, periodically provided to the IDPs, is used as a tool to track trends. RESULTS: Although avian WNV was identified, no human cases were diagnosed in the Washington, DC area. However, the establishment of a baseline quantification of meningitis facilitates identification of an epidemic in the future. The MSS designed in response to a specific threat is now in place to screen for other infrequently identified pathogens of concern. The MSS as a screen for aseptic meningitis, bacterial meningitis and post-craniotomy surgical site infections provides greater sensitivity than microbiology results alone. LESSONS LEARNED: This Infection Control program reacted to a singular concern by developing a prospective surveillance system for meningitis that increases case finding sensitivity, provides timely public health reporting, and contributes to nosocomial surveillance accuracy.