For health professionals: Tick-borne encephalitis (TBE)
Find detailed information on tick-borne encephalitis (TBE) for health professionals.
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What health professionals need to know about tick-borne encephalitis
TBE virus is caused by a single-stranded ribonucleic acid (RNA) virus from the family Flaviviridae. There have been 3 sub-types identified:
- Far Eastern
TBE virus is transmitted through the bite of an infected tick, primarily of the Ixodes ricinus and Ixodes persulcatus species.
Approximately 2 out of 3 cases of TBE infection are asymptomatic. When you have symptoms of TBE, the illness typically has a biphasic course.
The first phase is associated with symptoms like:
- muscular ache
The listed symptoms usually resolve within 1 week and correlate with viremia. They are also frequently subclinical or present as a nonspecific illness.
This phase is followed by a temporary remission lasting approximately 1 week.
There is a second neurologic phase after the virus has spread to the central nervous system. This happens in 20% to 30% of individuals. The second stage presents as aseptic meningitis (especially in children) or:
- some combination
Studies of patients with neurologic illness report that, overall, approximately:
- 50% have meningitis
- 40% have meningoencephalitis
- 10% have meningoencephalomyelitis
The European sub-type is associated with milder disease with:
- 20% to 30% of patients experiencing the second phase
- mortality rates of 0.5% to 2%
- severe neurological sequelae in up to 10% of patients
In children, the second phase of illness is usually limited to meningitis. However, adults older than 40 years are at increased risk of developing encephalitis. This is linked to higher mortality and long-lasting sequelae in those over the age of 60.
Far Eastern variety
The far eastern sub-type is associated with more severe disease (monophasic illness) with:
- no asymptomatic interval preceding the onset of neurological disease
- mortality rates of up to 35%
- higher rates of severe neurological sequelae
The Siberian sub-type is associated with a less severe disease with a fatality rate of 1% to 3%. There is a tendency for patients to develop chronic or extremely prolonged infections.
The diagnosis is usually based on:
- history of exposure to ticks within the previous 4 weeks
- clinical symptoms
- specific IgM and IgG antibodies to TBE, as measured by enzyme-linked immunosorbent assay (ELISA)
Antiviral antibodies are usually detectable at the beginning of the second phase.
Other specific tests are:
- nested reverse transcriptase polymerase chain reaction (nRT-PCR) to detect virus-specific nucleic acid
- western blots, performed in specialized laboratories
There are no effective antiviral drugs for TBE. Therefore, treatment consists of supportive care.
For more information
- Committee to Advise on Tropical Medicine and Travel
- European Centre for Disease Prevention and Control
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