What increase is due to unclear, but the weather and the availability of deer and rodents are important factors.
So far this year 144 cases of the disease have been reported, marking a significant increase. In August alone, 66 cases had been uncovered as of the 24th of the month, compared with 25 to 48 cases during the corresponding period between 2007 and 2010.
However it remains a mystery as to why the numbers are so high in comparison with other years.
Areas most affected are around Stockholm and Lake Mälaren, where experts point to the growing numbers and increased resilience of ticks as well as weather conditions this year, although it is still hard to pinpoint one specific reason.
Marika Hjerteblomsten Qvist, epidemiologist at SMI told Svenska Dagbladet,
”Ticks can handle cold and snowy winters quite well, but during that time there are fewer deer, so there is no direct connection.”
The weather is also relevant to how many people were camping in the countryside, which also affects the risk of being affected.
Encephalitis, is an inflammation of the brain, caused often by a virus carried in the saliva of ticks.
"Most people who get TBE don't even notice it. They may only have flu-like symptoms, but only about one percent of the ticks carry the virus, and even if you get bitten by one, it is not certain that you will get ill,” added Hjerteblomsten Qvist.