Lyme borreliosis is an infectious disease caused by the bacterium Borrelia burgdorferi . It is transmitted to humans through saliva when bitten by certain types of ticks (of the genus Ixodes) when they are infected.
In Belgium, it is estimated that 14% of ticks are infected. The Borrelia bacteria are usually found in the tick's intestine. When sucking blood, the bacteria move from the intestine to the salivary glands of the tick, which takes some time (usually one day). The risk of transmission of the bacteria therefore increases with the length of time the tick is attached. The risk appears low if the tick is removed within 12 to 24 hours. After a tick bite, the risk of developing the disease is considered to be about 1-3%.