MADISON, Wis. (AP) -- Wisconsin health officials say there was a significant increase in the number of reported Lyme disease cases in the state last year.

State Health Officer Dr. Sheri Johnson says there were 1,819 cases reported in 2007. She says that compares with 1,456 in 2006.

She says that, while Lyme disease has been reported in many areas around Wisconsin, most took place in the northwestern and west central regions of the state.

Johnson says that most people in Wisconsin who develop Lyme disease are exposed to infected ticks between May and August. She says the greatest risk of developing the illness is during June and July."

Lyme disease is caused by a bacteria carried by small ticks called deer ticks. Officials say it can cause debilitating arthritis as well as serious heart and nervous system problems.