Completeness of West Nile virus testing in patients with meningitis and encephalitis during an outbreak in Arizona, USA

Abstract

Accurate data on West Nile virus (WNV) cases help guide public health education and control activities, and impact regional WNV blood product screening procedures. During an outbreak of WNV disease in Arizona, records from patients with meningitis or encephalitis were reviewed to determine the proportion tested for WNV. Of 60 patients identified with meningitis or encephalitis, 24 (40%) were tested for WNV. Only 12 (28%) of 43 patients aged <50 years were tested for WNV compared to 12 (71%) of 17 patients aged ≥50 years (P<0·01). Patients with clinical signs of weakness or paralysis, elevated CSF protein, admitted to an inpatient facility, or discharged to a rehabilitation facility were also more likely to have WNV testing performed. The lack of testing in younger age groups and in those with less severe disease probably resulted in substantial underestimates of WNV neuroinvasive disease burden.

Initial and Long-Term Costs of Patients Hospitalized with West Nile Virus Disease

“…1 Our estimate of WNV costs is conservative as it does not account for costs incurred by nonhospitalized WNV cases or make any adjustment for the under diagnosis or underreporting of WNV disease cases. 1,23 To date, an estimated 18,775 non-hospitalized cases of WNV disease have been reported to CDC. If the cost estimate of a fever case (cost of one healthcare provider office visit, one diagnostic test, and 5 days off work) from Barber and others 13 is applied and adjusted to 2012 USD, the estimated total costs of non-hospitalized cases from 1999 to 2012 would bẽ $28 million or 3.6% of the total direct or indirect medical costs incurred by hospitalized WNV disease cases.…”

Lack of Evidence of Increased West Nile Virus Disease Severity in the United States in 2012

“…During an outbreak of WNV disease in Arizona, only 40% of patients presenting with a clinically compatible neuroinvasive illness were tested for WNV infection and older persons and those with more severe disease were more likely to be tested, suggesting testing biases. 23 Additionally, because ArboNET does not routinely collect information regarding clinical signs and symptoms or specific laboratory findings (e.g., cerebrospinal fluid findings), misclassification of the various syndromes caused by WNV (i.e., encephalitis, meningitis, acute flaccid paralysis, and uncomplicated fever) cannot be detected.…”

Neuroinvasive Arboviral Disease in the United States: 2003 to 2012

“…In addition, preconceptions about arboviral disease epidemiology may impact diagnostic practices, with La Crosse virus testing more likely to be performed on children in selected states and West Nile virus testing considered more in older adults. 54 Additionally, because ArboNET does not routinely collect information regarding clinical signs and symptoms or specific laboratory findings (eg, cerebrospinal fluid findings), misclassification as neuroinvasive disease or a specific clinical syndrome (ie, meningitis, encephalitis, or acute flaccid paralysis) cannot be detected. For example, spinal cord involvement resulting in acute flaccid paralysis has only rarely been described with La Crosse virus or other orthobunyaviruses but 10 cases of acute flaccid paralysis were reported after La Crosse virus infections in our series.…”