Lyme Disease, 2004
During 2004, reported Lyme disease cases increased to a record number of 1,023 (20.0 cases per 100,000 population). An additional 24 cases were classified as probable Lyme disease. Six hundred forty-four (63%) confirmed case-patients in 2004 were male. The median age of case-patients was 39 years (range, 1 to 94 years). Physician-diagnosed erythema migrans was present in 880 (86%) cases. Two hundred (20%) cases had at least one late manifestation of Lyme disease (including 132 with a history of objective joint swelling and 54 with cranial neuritis) and confirmation by a positive Western blot test. Onsets of illness peaked in July (35% of cases), corresponding to the peak activity of nymphal Ixodes scapularis (deer tick or black-legged tick) in mid-May through mid-July.
Four hundred forty-two (43%) cases occurred among residents of the Twin Cities metropolitan area. However, only 40 (5%) of 736 case-patients with known exposure likely were exposed to infected I. scapularis in metropolitan counties, primarily Anoka and Washington Counties. Most case-patients either resided in or traveled to endemic counties in east-central Minnesota or western Wisconsin. As in 2003, Crow Wing County continued to have the highest number of Lyme disease case exposures (153 [21%] of 736 cases). Lyme disease risk appears to be spreading north and west, indicated by an increasing number of exposures in counties with a history of sporadic Lyme disease case exposures (Becker, Hubbard and Itasca Counties).
For a more detailed discussion of Lyme disease and other tick-borne diseases in Minnesota, including a map of high-risk areas, see “Dramatic Increase in Lyme Disease and Other Tick-borne Diseases, 2004” in the May/ June 2005 issue (PDF: 153KB/16 pages) of the Disease Control Newsletter.
Note: For up to date information on Lyme Disease see Lyme Disease (Borrelia burgdorferi)
Go to full issue: DCN, July/August 2005: Volume 33, Number 4