The number of people in the Netherlands with Lyme’s disease continues to rise and the infection total has quadrupled over the past 20 years, the public health council RIVM said on Monday.

In total, 27,000 were diagnosed with Lyme’s last year, a rise of 2,000 on 2014 when the RIVM last reported on the prevalence of the tick-borne disease.

The figures were released on Monday at the start of a week-long campaign to warn people of the dangers of tick bites. Every year, 1.3 million people are bitten by ticks while walking in woods, dunes or even the garden. Left untreated, Lyme can affect the joints, heart and central nervous system.

The RIVM and other bodies researching ticks have set up a special monitor in an effort to better understand the Dutch tick population. People can use the monitor to check their symptoms and see where most infected ticks have been found.

The RIVM recommends people check their skin and clothing for ticks if they have been in the countryside. People are also advised to wear long sleeves and tuck their trousers into their socks.