|
.gif) |
Encephalitis, Arboviral
1996 Case Definition
Revised September 1996
Clinical description
Arboviral infection may result in a febrile illness
of variable severity associated with neurologic symptoms ranging
from headache to aseptic meningitis or encephalitis. Arboviral encephalitis
cannot be distinguished clinically from other central nervous system
(CNS) infections. Symptoms can include headache, confusion or other
alteration in sensorium, nausea, and vomiting. Signs may include
fever, meningismus, cranial nerve palsies, paresis or paralysis,
sensory deficits, altered reflexes, convulsions, abnormal movements,
and coma of varying degree.
Laboratory criteria for diagnosis
- Fourfold or greater change in serum antibody
titer, or
- Isolation of virus from or demonstration of
viral antigen or genomic sequences in tissue, blood, cerebrospinal
fluid (CSF), or other body fluid, or
- Specific immunoglobulin M (IgM) antibody by
enzyme immunoassay (EIA) antibody captured in CSF or serum.
Serum IgM antibodies alone should be confirmed by demonstration
of immunoglobulin G antibodies by another serologic assay (e.g.,
neutralization or hemagglutination inhibition).
Case classification
Probable: a clinically
compatible case occurring during a period when arboviral transmission
is likely, and with the following supportive serology: a stable (less
than or equal to twofold change) elevated antibody titer to an arbovirus
(e.g., greater than or equal to 320 by hemagglutination inhibition,
greater than or equal to 128 by complement fixation, greater than
or equal to 256 by immunofluorescence, and greater than or equal
to 160 by neutralization, or greater than or equal to 400 by enzyme
immunoassay IgM).
Confirmed: a clinically compatible case
that is laboratory confirmed
Comment
The seasonality of arboviral transmission is variable
and depends on the geographic location of exposure, the specific
cycles of viral transmission, and local climatic conditions. Reporting
should be etiology-specific (see below; the four encephalitides printed
in bold are nationally reportable to CDC):
- St. Louis encephalitis
- Western equine encephalitis
- Eastern equine encephalitis
- California encephalitis (includes
infections from the following viruses: LaCrosse, Jamestown
Canyon, Snowshoe Hare, Trivittatus, Keystone, and California
encephalitis viruses)
- Powassan encephalitis
West Nile encephalitis
- Other CNS infections transmitted by mosquitoes,
ticks, or midges (e.g., Venezuelan equine encephalitis and
Cache Valley encephalitis)
See also:
Printable
Version |
|
