Tick-borne encephalitis (TBE) is an infectious disease caused by the tick-borne encephalitis virus (TBEV). It belongs to the flavivirus family and is transmitted to humans through the bite of infected ticks, most commonly Ixodes ricinus and Ixodes persulcatus. The disease is most frequently reported in Europe and Asia, particularly in regions with a high tick population.
Tick-borne encephalitis causes inflammation of the central nervous system (the brain and spinal cord), known as encephalitis. This condition can lead to a wide range of symptoms, from mild flu-like manifestations such as fever, fatigue, and headache, to severe neurological complications including loss of consciousness, seizures, or paralysis. In some cases, tick-borne encephalitis can be fatal.
It is important to note that not all tick bites result in tick-borne encephalitis—only a small proportion of ticks carry the virus. However, if a person is bitten by an infected tick and transmission occurs, the disease can develop into a serious and potentially life-threatening condition.
Tick-borne encephalitis is caused by the tick-borne encephalitis virus (TBEV), which is transmitted to humans through the bite of infected ticks (Ixodes ricinus and Ixodes persulcatus). These tick species are most commonly found in forests, grasslands, and rural areas, making people who spend time in nature particularly vulnerable.
The tick life cycle and their ability to transmit the virus depend on various factors such as temperature, humidity, and the availability of host animals whose blood they feed on. The virus is transmitted during the tick’s blood meal from an infected animal. Humans and animals can become infected but do not transmit the virus further.
Geographically, the prevalence of tick-borne encephalitis corresponds to the distribution of infected ticks. The disease is widespread across Europe, Asia, and parts of Siberia. The highest number of cases is reported in Central Europe and Northern Asia. The greatest risk period is late spring to early summer, when tick activity is at its peak.
Tick-borne encephalitis often develops in two phases. After infection with TBEV, the first symptoms typically appear within 1–2 weeks and resemble those of influenza. These may include high fever, headache, fatigue, muscle and joint pain, loss of appetite, and general malaise. This phase usually lasts several days to a week, after which the patient may temporarily feel better.
However, in approximately 30% of infected individuals, a second phase develops after a symptom-free interval of 1–2 weeks. During this stage, the virus affects the central nervous system and causes encephalitis (inflammation of the brain). Symptoms may vary depending on the affected areas of the brain and can include severe headache, fever, vomiting, chills, loss of consciousness, seizures, visual disturbances, and other neurological symptoms.
In severe cases, complications such as respiratory failure, cardiovascular disturbances, and other life-threatening conditions may occur. This stage requires immediate medical attention.
Tick-borne encephalitis virus is classified into three main genotypes based on geographic distribution and genetic characteristics: European (Western), Siberian, and Far Eastern (Asian). While clinical symptoms are generally similar, disease severity may vary.
The European (Western) genotype is widespread across Europe and is usually associated with a milder course of illness and fewer severe complications. Nevertheless, it can still cause serious encephalitis, especially in older individuals.
The Siberian genotype, prevalent in Siberia and other parts of Asia, is associated with more severe disease and a higher risk of mortality. Long-term complications such as muscle weakness, paralysis, and brain damage have been reported.
The Far Eastern genotype, found in East Asia including Japan, China, and Korea, is considered the most severe. It is associated with high mortality rates and a significant risk of long-term neurological complications, including paralysis, brain damage, and psychiatric disorders.
Tick-borne encephalitis is diagnosed based on clinical symptoms, patient history (including possible exposure to ticks during the tick season in endemic areas), and laboratory test results. Laboratory confirmation involves detecting specific antibodies produced in response to TBEV infection in the patient’s blood.
There is no specific antiviral treatment for tick-borne encephalitis, so therapy is primarily symptomatic and supportive. Treatment focuses on reducing fever and pain, maintaining proper hydration, and supporting vital bodily functions while the immune system fights the infection. In severe cases involving central nervous system impairment, hospitalization and intensive care may be required, including respiratory support and seizure management.
Prevention is a crucial aspect of managing tick-borne encephalitis. Preventive measures include avoiding tick-infested areas, using tick repellents, wearing protective clothing in natural environments, and vaccination against tick-borne encephalitis, which is considered a safe and highly effective method of protection.
The long-term effects of tick-borne encephalitis vary depending on the severity of the disease. Individual outcomes depend on factors such as overall health, age, and immune system function.
Some patients may experience serious complications related to brain damage, leading to long-term symptoms such as persistent headaches, muscle weakness, impaired coordination, epilepsy, and cognitive deficits. In severe cases, complications may include paralysis, psychiatric disorders, and permanent neurological disability.
A subset of patients may develop post-infectious syndrome, characterized by chronic fatigue, concentration and memory problems, and emotional disturbances such as depression or anxiety. These symptoms can persist for months or even years after recovery.
It is important to emphasize that not all cases of tick-borne encephalitis are severe. Many individuals experience only mild flu-like symptoms and recover fully without long-term consequences. However, due to the potentially serious nature of the disease and its long-lasting effects, tick-borne encephalitis should be regarded as a significant public health concern requiring proper prevention and management.
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