See
the case definition (2004) for Neuroinvasive
and Non-Neuroinvasive Domestic Arboviral Diseases. From the CDC Epidemiology
Program Office.
Total Human Cases Reported to CDC: these numbers reflect both mild and severe human disease cases occurring between January 1, 2009 to December 31, 2009 as reported through November 17, 2009 to ArboNET by state and local health departments. ArboNET is the national, electronic surveillance system established by CDC to assist states in tracking West Nile virus and other mosquito-borne viruses. Information regarding 2009 virus/disease activity is posted when such cases are reported to CDC.
Of the 608 cases, 324 (53%) were reported as West Nile meningitis or encephalitis (neuroinvasive disease), 265 (44%) were reported as West Nile fever (milder disease), and 19 (3%) were clinically unspecified at this time. Please refer to state health department web sites for further details regarding state case totals.
Note: the
high proportion of neuroinvasive disease cases among
reported cases of West Nile virus disease reflects
surveillance reporting bias. Serious cases are more
likely to be reported than mild cases. Also, the surveillance
system is not designed to detect asymptomatic infections. Data
from population-based surveys indicate that among all
people who become infected with West Nile virus (including
people with asymptomatic infections) less than 1% will
develop severe neuroinvasive disease. See: Mostashari
F, Bunning ML, Kitsutani PT, et al. Epidemic West Nile
Encephalitis, New York, 1999: Results of a household-based
seroepidemiological survey. Lancet 2001;358:261-264.
1999|2000|2001|2002|2003|2004|2005|2006|2007|2008
|2009
