Severe tick-borne encephalitis in Slovenia: epidemiological, clinical and laboratory findings.

The aim of this retrospective study was to determine epidemiological, clinical and laboratory characteristics in adult patients with the severe form of tick-borne encephalitis. Thirty-one patients with a severe course of disease admitted to the intensive care unit of the Department of Infectious Diseases at the University Medical Centre Ljubljana, Slovenia, between 1996 and 2000 were included in the study. Tick-borne encephalitis virus infection was confirmed by the demonstration of specific IgM and IgG antibodies in serum using routine serological screening tests. All the patients had specific IgM antibodies at admission and IgG antibodies were present in 90.3%. Nineteen patients suffered from severe meningoencephalitis, 11 from meningoencephalomyelitis, and dysfunction of the autonomic nervous system was found in one patient. The mortality rate was 3.3%. Tick bite was recorded in 58% and a characteristic biphasic course of the disease was found in 16 patients. The median cerebrospinal fluid leukocyte count was 112 x 10(6)/l, and in 93.5% of patients the cerebrospinal fluid protein concentration was greater than the cut-off value of 0.45 g/l. The findings of the present study indicate some clinical, epidemiological and laboratory distinctions between published data on the mild or moderately severe form of tick-borne encephalitis and our patients with severe disease.