Dr. Murai Éva - Gubányi András szerk.: Parasitologia Hungarica 29-30. (Budapest, 1997)

accompanied by sore throat, the pharyngeal structures are usually inflamed and sometimes conjunctival injection is also present. In such cases, medical examination usually yields the diagnosis of summer influenza. (Numerous textbooks describe the above signs of the first phase as respiratory symptoms. Here it is important to mention that TBE is not accompanied by coughing.) These first atypical symptoms can be expected to occur on days 7-14 after the tick bite, and disappear within one week even without treatment. It should be emphasised that in the overwhelming majority of the cases the disease does not get beyond the first phase, and disappears without raising the suspicion of TBE virus infection in anyone. In one-fourth of the cases, if the first phase is deficient in clinical symptoms, the disease takes a monophasic course. The first phase is followed by an asymptomatic period lasting a couple of days, and then by the second phase. The second phase begins when the virus has entered the nervous system and starts to multiply there in weeks 2-4 after the tick bite. That phase starts with a pyrexial spike higher than that in the first phase, accompanied by dizziness, intense headache and, almost invariably, vomiting. The patients' movement becomes clumsy, and they easily stumble and fall. Occipital stiffness develops. The patients are usually somnolent but may as well be extremely restless and irritable. Restlessness and irritability may be followed by unconsciousness at any time. Convulsion occurs in a very small proportion of hospitalised patients. Based upon the clinical symptoms, meningitic, meningoencephalitic and meningoencephalomyelitic forms of the disease can be distinguished. Benign meningitis is more common in childhood. A polio-like clinical picture may occur at any age but is relatively uncommon. In every fifth hospitalised patient, encephalitis is accompanied by paralysis. In half of the cases involving paralysis, severe residual symptoms are left behind after recovery. The disease process most frequently affects the proximal muscle groups, almost always the shoulder girdle. Paralysis occurs more frequently in muscle groups which are subjected to stress during the prodromal phase. In the most severe cases the respiratory muscles also may become paralysed. Death usually sets in on day 2-30 of the nervous symptoms, as a consequence of progressive spino-bulbar paralysis or tetraparesis accompanied by respiratory paralysis (Jellinger 1981). The other extreme is when the virus infection passes off in an asymptomatic manner, which can be detected only by sero-epidemiological investigations. For each diagnosed case of TBE there are four symptom-deficient cases of unrecognised infection (Gustafson et al. 1992). Some of the meningitic forms are also likely to remain undiagnosed, as after the intense headache and vomiting the symptoms disappear without any treatment. That benign form is common especially in childhood. However, even benign infections of a less severe course often leave behind a lasting headache, slight memory disturbances, narrowed cognitive functions, and depression. Permanent EEG abnormalities can be detected after apparent clinical recovery (Juhász and Szirmai 1993). The severity of the clinical picture may vary by period and region, as indicated by the experience gained at the Szent László Hospital (Tables 1-3). It must be added immediately, however, that not in all areas of the country has this "attenuation" of the disease been observed. Today we do not yet know what factors are responsible for differences in the course of TBE, as individual virus strains may also differ in infectivity, affinity to the nervous system, and invasive properties. However, so far only the virus strains originating from areas beyond the Ural Mountains and the European strains could be demonstrated to differ in the severity of clinical symptoms produced.