Lyme disease is an illness caused by a bacterium called Borrelia burgdorferi, which is transmitted by the bite of an infected tick. The bacterium is usually carried by birds, mice, squirrels, and other small animals. Ticks become infected by the bacterium when they feed on infected animals. The bacterium can be passed to humans when they get bitten by an infected tick. Under normal circumstances, Lyme disease cannot be passed from human to human. Pets (cats and dogs) can get Lyme disease as well, but they don't appear to pass it onto humans. However, they can bring infected ticks into the home.
You may come into contact with a tick simply by brushing against vegetation. The risk of contact increases between early spring and late fall. The winter months don't always offer protection from ticks if the temperature is 4°C or more and there is no snow. It's important to note that not all ticks carry Lyme disease, and the chance of getting Lyme disease from an infected tick is greatly reduced by removing ticks within 24 to 36 hours of attachment.