Clinical course of the disease

The frequency of illness is subject to seasonal fluctuations and arises from the activity of ticks. Mild winters and humid springs promote the incidence of ticks. Risk of infection can begin as early as February and not end until November.

The illness progresses in two phases; in up to 20% of the cases the first phase is not perceived by patients.
During the two-phase progression, the so-called first phase of the illness occurs after an incubation period of 6 to14 days; this is when the virus enters the bloodstream. Patients complain of general symptoms, such as temperature increase (usually under 39˚C), headaches, overall weakness, fatigue, intestinal problems, cough and sniffles; symptoms often indicative of the common cold. After a frequently symptom-free interval of between 2 and up to a maximum of 8 days, symptoms indicating the affection of the nervous system appear. This happens when the virus succeeds in breaching the blood-brain barrier and infects the brain. Another temperature increase (usually over 39˚C) ensues, with typical additional symptoms being aggravated headaches, neck stiffness, impaired consciousness, delirium (a dramatically progressive mental disorder with dream-like clouding of the consciousness), cranial nerve paralysis, coordination problems and paralysis of the arms and legs. Ultimately, paralysis of the respiratory musculature can occur. Intensive treatment, including artificial respiration, is then essential.

Disease forms of TBE in adults

1.		Meningitis Meningitis comprising fever, stiffness of the neck, sensitivity to light, and nausea/vomiting without affection of the cerebral tissue. Healing without permanent damage; no immediate threat to life.
2.		Encephalitis (the most frequent form) Diffuse inflammation, often of the entire cerebral tissue and frequently with cerebral swelling and bleeding. Especially affected are the basal ganglia, the infection of which can result in a clouding of the consciousness, leading to delirium and coma, paralysis and apraxia (difficulty moving) of the arms and/or legs, epileptic seizures, Parkinson-like trembling and stiffness, as well as breathing difficulties if the brain stem has been affected. There is 0.8-2% fatality rate.
3.		Radiculomyelitis – Poliomyelitis-like The inflammation of the spinal cord and the nerve roots results in paralysis with amyotrophia (wasting away of the muscles), nerve pain, and/or paraplegia with a disruption of bowel movement and urination. Up to 20% lethality.

A serious complication outside of the nervous system can be coagulopathies, wherein internal bleeding leads to shock. Concomitant inflammations of the liver and myocardium are also possible.

What are the consequential damages?
The dying off of the nerve cells (spinal cord and/or cerebral tissue) can cause permanent disability in forms 2 and 3. In children, it can lead to developmental problems, epileptic seizures often requiring life-long medication, and memory and perception problems, Parkinson-like movement disorders, paraplegia, respiratory paralysis and muscle paralysis, which can result in an inability to work, the need of permanent care and dependence on a wheelchair and respirator.

The seemingly mild meningeal form also has its dangers.
Case example: A patient has overcome the mildest form of TBE, meningitis, and spends several days and up to two to three weeks in the hospital. Due to professional care and bed rest, this patient soon feels better.

However, when the patient attempts to resume his usual daily activities, he quickly notices that he is experiencing problems concentrating, and listlessness. If this person does not feel better in one to two months, he becomes anxious, i.e., an additional state of depression worsens his condition. In the majority of cases, this development was observed over a time frame of up to one year. Patients then feel forced to isolate themselves and are often wary of speaking with anyone about this sensitive problem.