Between three and 30 days after someone is bitten, they can develop a circular rash around the area of the bite.
It can then lead to a range of more serious symptoms, including a flu-like illness with tiredness, headaches and muscle or joint pain.
If the condition is not treated, symptoms may develop months or years later. It can cause neurological symptoms, such as temporary paralysis of the facial muscles, and it can also trigger symptoms similar to those of fibromyalgia or chronic fatigue syndrome.
Lyme disease is difficult to diagnose but a blood test is available. It can be treated with antibiotics but is difficult to cure if discovered late.