Viral encephalitis (and Tick-borne)

Viral encephalitis1

Clinical criteria
Any person with altered mental state (altered level of consciousness, agitation, lethargy) for longer than 24 hours and displaying two or more of the following six features:
- Fever >38o or history of fever
- Seizures and/or focal neurological findings (with evidence of brain parenchyma involvement)
- Cerebrospinal fluid (CSF) pleocytosis with predominant lymphocytes and/or elevated protein with a negative Gram stain and culture
- Abnormal EEG findings indicative of encephalitis
- Abnormal neuroimaging findings compatible with encephalitis
- No alternative diagnosis (microbiological or non-infectious)

Laboratory criteria
At least ONE of the following three criteria:
- Detection of viral nucleic acid in CSF by PCR
- Culture of virus from CSF
- Serological evidence of acute infection with a virus known to cause viral encephalitis

Epidemiological criteria

Case classification
A. Possible case
Any person meeting the clinical criteria
B. Probable case
C. Confirmed case
Any person meeting the clinical and the laboratory criteria 

Tick-borne encephalitis (TBE)2

Clinical Criteria:
Any person with symptoms of inflammation of the CNS (e.g. meningitis, meningo- encephalitis, encephalomyelitis, encephalo-radiculitis)

Laboratory Criteria for a Confirmed Case3
At least ONE of the following five criteria:
- TBE specific IgM AND IgG antibodies in blood
- TBE specific IgM antibodies in CSF
- Sero-conversion or four fold increase of TBE-specific antibodies in paired serum samples
- Detection of TBE viral nucleic acid in a clinical specimen
- Isolation of TBE virus from clinical specimen

Laboratory Criteria for a Probable Case3
- Detection of TBE-specific IgM-antibodies in a serum sample

Epidemiological Criteria
Exposure to a common source (unpasteurised dairy products)

A. Possible
B. Probable
Any person meeting the clinical criteria and the laboratory criteria for a probable case
Any person meeting the clinical criteria and with an epidemiological link
C. Confirmed
Any person meeting the clinical and laboratory criteria for case confirmation 

1Notification of viral encephalitis due to Tick-borne encephalitis (TBE) should be notified using the case definition below. Notification of viral encephalitis due to another listed pathogen should be notified under the relevant disease (e.g. West Nile virus, Chikungunya virus)

2The following definition should be used for reporting of viral encephalitis caused by Tick-borne encephalitis (TBE) virus

3Serological results should be interpreted according to the vaccination status and previous exposure to other flaviviral infections. Confirmed cases in such situations should be validated by serum neutralization assay or other equivalent assays 

Current as of: 24 January 2019