Tick-borne encephalitis (TBE) is a viral infection spread to humans by the bite of a type of parasite known as a tick.
A tick looks like a small black or dark brown spider.
Initial symptoms of TBE are similar to flu and include:
In around 1 in 3 cases of TBE initial symptoms are then followed by additional symptoms.
These symptoms are caused by the virus spreading to the layer of protective tissue that covers the brain and spinal cord (meningitis) and /or the brain itself (encephalitis).
In some case these ‘second-stage’ symptoms can be relatively mild, such as:
- feeling sick
- being sick
- increased sensitivity to bright lights
While in others the second-stage symptoms can be more wide-ranging, such as:
- seizures (fits)
- inability to speak
- inability to control physical movements
Read more about the symptoms of tick-borne encephalitis.
There is currently no cure for TBE so treatment is based on helping relieve symptoms and make a person feel as comfortable as possible until the infection has passed.
If a person only experiences initial symptoms of TBE then no treatment, other than over-the-counter painkiller ibuprofen to relieve symptoms such as fever and headache, is required.
If a person develops second-stage symptoms, then depending on the severity, they may need to be admitted to hospital. Hospital treatment may involve providing supportive treatments such as intravenous fluids, help with breathing and nursing care.
Read more about the treatment of tick-borne encephalitis.
How can you catch it
Ticks that cause TBE are not found in the UK.
They are mainly found in forested areas of central, eastern and northern Europe, including Austria, Bosnia-Herzegovina, Croatia, Estonia, Latvia, Czech Republic, Slovakia, Germany, Hungary, Macedonia, Montenegro, Poland, Serbia, Slovenia, Switzerland, Russia and Ukraine.
There are also two sub-types of TBE known as:
- Far Eastern – found in eastern Russia during spring and summer and in some countries in East Asia, particularly forested regions of China and Japan
- Siberian – found in Siberia
The TBE virus is found naturally in small animals such as mice and voles and in domestic animals such as sheep, goats and cattle. Ticks are the main carriers of the virus, picking up the virus when they feed on the blood of an infected animal. Once the tick is infected with the virus, it carries this for life.
Humans become infected with TBE when they are bitten by an infected tick. The virus is present in the tick’s saliva, which contains a natural anaesthetic, so you may not notice you have been bitten. It is important to check your body regularly for ticks when in risk areas.
Ticks live in forests, woods, grasslands, riverside meadows, marshes, brushwood and shrublands. They usually live in the undergrowth, where they can easily get onto the clothes or skin of passers-by.
Very rarely, drinking unpasteurised milk from infected animals, especially goats, can expose you to the TBE virus.
A seasonal disease
TBE is a seasonal disease as different seasons of the year have a significant impact on tick activity.
In Europe tick activity starts in spring once the temperature reaches 6C (42.8F) and lasts until November when temperatures fall.
Tick activity peaks in May/June and September/October, but in fact most cases of TBE occur during summer months as this is when people are most likely to go hiking, camping and so on.
Some experts are predicting TBE could become more widespread due to climate change resulting in a trend of milder winters and warmer springs. This in turn would mean the ‘window of opportunity’ for tick activity would grow longer.
If the infection spreads to the brain there is a risk of a person experiencing long-term (and possibly permanent) after effects, such as:
- worsening memory
- problems with concentration and a shortening attention span
- changes in behaviour, such as becoming more impulsive and having poor judgement
These sort of long-term after effects occur in around 1 in 10 people who have contracted TBE.
Read more about complications of tick-borne encephalitis.
There is a vaccine that provides protection against TBE in around 9 out of 10 people who receive it. The vaccine is not given as part of the routine childhood vaccination schedule.
It is usually only recommended for people who are planning to work in, or travel in, parts of the world known to have moderate to high levels of infected ticks.
You can also protect yourself against ticks by taking common sense precautions, such as:
- Wear long-sleeved tops and long trousers (tucked into socks). You can also treat your clothes with insecticides such as permethrin.
- Apply insect repellent containing DEET to exposed skin.
- Check your body for ticks regularly. Common places to find them are the hair line, behind the ears, elbows, backs of knees, the groin and armpits.
Read more about preventing tick-borne encephalitis and the tick-borne encephalitis vaccine.
Who is affected
There are an average 3,000 hospital admissions due to TBE in Europe every year (not including Russia).
People who regularly work in rural areas, such as woodcutters, farmers, and hunters, have an increased risk of exposure to TBE.
Hikers and campers in these areas can also have an increased risk.
According to the Health Protection Agency no travellers from England have ever been infected with TBE.
But this could change in future if the disease becomes more widespread due to climate change. So it is still recommended you are vaccinated if you are at a potentially high risk of exposure.
For most people with TBE the outlook is good. The infection can be unpleasant but usually passes within eight days.
But for the one third of people who experience the second stage of infection the outlook is much less favourable. Symptoms can persist for months and though uncommon, the infection can sometimes be fatal.
It is estimated that around 1 in 50 people who catch TBE will die from it.