Can't see the film? Watch it here.
For The One Show, Dr Sarah Jarvis has been finding out about Lyme disease.
Lyme disease is caused by bacteria called Borrelia burgdorferi, it is transmitted to humans by ticks, and if not treated can cause serious health issues.
Watch Sarah's film, above.
In her film, Sarah told us that a small but growing number of us - estimated by the Health Protection Agency as up to 3000 people per year - are becoming infected, often after a walk in the countryside.
The good news is, if it's caught early Lyme disease is really easy to treat, said Sarah. Only one in three ticks carry the bad bacteria, and if you remove the tick (the best way is with tweezers) within 12 hours of being bitten, you significantly reduce the chance of being infected.