Belonging to the genus Flavivirus, tick-borne encephalitis (TBE) is transmitted by the bite of an infected arthropod, specifically mosquitoes and ticks. The highest number of cases lie in Eastern Europe and Russia. Ixodes ricinus is the tick vector for both tick-borne encephalitis as well as Lyme disease in Europe, therefore coinfection is possible.
Fever, headache, fatigue, and malaise tend to occur and last for about five days. Following a short period of symptom-free time, more severe manifestations may develop including meningitis, encephalitis, myelitis, and cranial neuritis. Death rate for TBE is about one percent. However about one-third of patients experience lasting symptoms, primarily neuropsychiatric.
The ELISA test can detect IgM and IgG antibodies to TBE. If it is too early for antibody development, but TBE is suspected, polymerase chain reaction (PCR) tests may be done on the serum. While lumbar puncture, brain MRI and EEG may be done, they all produce nonspecific findings and diagnosis cannot be based solely on them. Moderate pleocytosis and increased albumin can be found in the cerebrospinal fluid; abnormalities in the thalamus, cerebellum, and brainstem in MRI may be shown as well.