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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 infection with other neurotropic viruses. Symptoms may include headache, confusion or other alterations in sensorium, nausea, or vomiting. Signs may include evidence of elevated intracranial pressure or meningeal irritation, cranial nerve palsies, paresis or paralysis, altered reflexes, or convulsions. (See Aseptic Meningitis and Encephalitis, Primary.)
Probable: a clinically compatible illness occurring during a period when arbovirus transmission is likely to occur, and with the following supportive serology: a stable (twofold or greater 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, greater than or equal to 160 by neutralization, or a positive serologic result by enzyme immunoassay (EIA)
Confirmed: a clinically compatible illness that is laboratory confirmed
The time of year in which arboviral transmission is likely to occur depends on the geographic location of exposure, the specific cycle of virus transmission, and local climatic conditions.
Arboviruses causing encephalitis include the following:
Encephalitis or meningoencephalitis that follows or occurs in combination with other viral illnesses that are not central nervous system illnesses, or after vaccine is administered. Symptoms may be due to hypersensitivity reaction. Primary encephalitis is excluded.
Confirmed: a clinically compatible illness diagnosed by a physician as postinfectious (or parainfectious) encephalitis
Laboratory studies are important in clinical diagnosis but are not required for reporting purposes.
returnAn illness in which encephalitis is the major manifestation. Symptoms are due to direct invasion and replication of the infectious agent in the central nervous system, resulting in objective clinical evidence of cerebral or cerebellar dysfunction. Postinfectious (or parainfectious) encephalitis is excluded.
Confirmed: a clinically compatible illness diagnosed by a physician as primary encephalitis
Laboratory studies are important in clinical diagnosis but are not required for reporting purposes.
Primary encephalitis is a category used for reporting to the NNDSS. This category includes arboviral encephalitis and primary encephalitis of unspecified cause.
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