Tick-borne encephalitis

A viral infectious disease spread by ticks

Tick-borne encephalitis (TBE) is a viral infectious disease involving the central nervous system. The disease is caused by the tick-borne encephalitis virus (TBEV), a member of the genus Flavivirus. TBE is primarily transmitted to humans through the bite of infected ticks, particularly the Ixodes ricinus and Ixodes persulcatus species. The disease is endemic in parts of Europe and Asia.

Virology

The tick-borne encephalitis virus is a positive-sense single-stranded RNA virus. It belongs to the family Flaviviridae, which also includes other notable viruses such as the West Nile virus, Dengue virus, and Zika virus. TBEV is divided into three subtypes: European, Siberian, and Far Eastern, each associated with different geographical regions and clinical outcomes.

Transmission

TBE is primarily transmitted through the bite of infected ticks. The Ixodes ricinus tick is the main vector in Europe, while Ixodes persulcatus is prevalent in Asia. In rare cases, the virus can also be transmitted through the consumption of unpasteurized dairy products from infected animals. Human-to-human transmission is extremely rare.

Epidemiology

TBE is endemic in many parts of Europe and Asia, with thousands of cases reported annually. The highest incidence rates are found in Russia, the Baltic states, and Central Europe. The disease is most commonly reported during the spring and summer months when tick activity is at its peak.

Clinical Features

The clinical course of TBE can be divided into two phases. The first phase, which occurs after an incubation period of 7-14 days, is characterized by nonspecific symptoms such as fever, fatigue, headache, and muscle aches. After a brief remission, the second phase may occur, involving neurological symptoms such as meningitis, encephalitis, or meningoencephalitis. Severe cases can lead to long-term neurological sequelae or even death.

Diagnosis

Diagnosis of TBE is based on clinical presentation and confirmed by laboratory testing. Serological tests to detect specific antibodies against TBEV in the blood or cerebrospinal fluid are commonly used. Polymerase chain reaction (PCR) testing can also be employed to detect viral RNA.

Prevention

Preventive measures include avoiding tick bites by wearing protective clothing, using insect repellents, and performing regular tick checks. Vaccination is available and recommended for people living in or traveling to endemic areas. The vaccine is effective against all subtypes of TBEV.

Treatment

There is no specific antiviral treatment for TBE. Management is supportive and focuses on alleviating symptoms. Hospitalization may be required for severe cases, and treatment may include pain relief, hydration, and monitoring for complications.

Prognosis

The prognosis of TBE varies depending on the severity of the disease and the patient's age and health status. While many patients recover fully, some may experience long-term neurological complications. The case fatality rate is higher for the Far Eastern subtype compared to the European subtype.

Related pages

• Flavivirus
• Encephalitis
• Tick
• Viral infection

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