Lyme Disease, 2003

During 2003, reported Lyme disease cases decreased to 473 (9.4 cases per 100,000 population) from a record 867 cases (17.6 per 100,000) in 2002. An additional 31 cases were classified as probable Lyme disease. Two hundred seventy-four (58%) confirmed case patients in 2003 were male. The median age of case-patients was 33 years (range, 1 to 90 years). Physician- diagnosed erythema migrans was present in 393 (83%) cases. One hundred seven (23%) cases had at least one late manifestation of Lyme disease (including 82 with a history of objective joint swelling and 19 with cranial neuritis) and confirmation by a positive Western blot test. Onsets of illness peaked in July (39% of cases), corresponding to the peak activity of nymphal Ixodes scapularis (deer tick or black-legged tick) in mid-May through mid-July.

Two hundred thirty-eight (50%) cases occurred among residents of the Twin Cities metropolitan area. However, only 50 (15%) of 331 case-patients with known exposure data likely were exposed to infected I. scapularis in metropolitan counties, primarily Anoka, Washington, and extreme northern Ramsey Counties. Most case-patients either resided in or traveled to endemic counties in east-central Minnesota or western Wisconsin. As in 2002, Crow Wing County continued to have the highest number of Lyme disease case exposures (60 [18%] of 331 case patients).

For a more detailed discussion of Lyme disease and other tick-borne diseases in Minnesota, including a map of high-risk areas, see “Lyme Disease and Anaplasmosis in Minnesota, 2003” in the March/April 2004 issue (vol. 32, no. 2) of the Disease Control Newsletter.

• For up to date information see: Lyme disease
• Full issue>> Annual Summary of Communicable Diseases Reported to the Minnesota Department of Health, 2003