[Epidemiology and progress of early summer meningoencephalitis in Baden-Württemberg between 1994 and 1999. A prospective study of 731 patients]

Abstract

Background and objective: Tick-borne encephalitis (TBE) may develop into a serious disease leading to invalidism in a considerable proportion of patients. Detailed clinical and epidemiological data about the risks of TBE in Baden-Württemberg have been missing. A prospective study was started in 1994 to investigate the areas of risk in this part of Germany and to describe the clinical course and prognosis of TBE.

Patients and methods: Doctors at all departments of Internal Medicine, Neurology and Paediatrics, at diagnostic laboratories and the departments of public health were asked to participate in this study. Data were recorded by means of a questionnaire.

Results: Between 1994 and 1999, 771 patients with TBE were recorded. Detailed clinical and epidemiological data were available for 731 patients. In 88% of the patients infection took place during leisure time activity, two thirds of infections occurring between June and August. The median incubation period was 8 days with a range of 4-28 days. 71% of the patients reported a prodromal stage with flu-like symptoms. TBE manifested as isolated meningitis in 47%, as meningoencephalitis in 42% and as meningoencephalomyelitis in 11%. With increasing age the number with a serious course of disease also increased. The most frequent symptoms were impairment of consciousness, ataxia and pareses of the limbs. In the children, the course of disease and prognosis was much better than in adults. Of 230 patients who were re-examined between 1 and 5 years after the acute illness 23% suffered from persisting moderate or severe symptoms. The death rate was about 1.4%.

Conclusion: In Baden-Württemberg, tick bites are associated with a high risk of tick-borne encephalitis and severe neurological complications. Therefore, active immunization is recommended for all persons exposing themselves to ticks. Persisting complications after TBE are by far more common than serious complications after active immunization.