Some infected people have no symptoms at all. However, the first sign is usually a pink or red spot at the site of the tick bite. This appears between 3 and 30 days after biting, and expands steadily, often with an inflamed red border.

As the rash spreads, the previously affected skin may return to a more normal appearance forming an expanding 'target pattern' with a flat border, which may become quite large (10-70 cms) if left untreated. This rash is called 'erythema migrans'. Some erythema migrans rashes may not have a target-type appearance, but can be more evenly colored. A rash that develops within a day of a bite is not erythema migrans, but could be due to a sensitivity reaction, or a more common type of skin infection.

The following symptoms may also develop in the first few weeks of an infection:

• tiredness/fatigue,
• generally feeling sick,
• headache,
• fever,
• aches in muscles and joints,
• a stiff neck, and
• swollen glands (enlarged lymph nodes).

In rare cases there are more serious complications. These can affect the nervous system, joints, heart and other tissues.