Lyme Disease, 2014
Lyme disease is a bacterial infection caused by Borrelia burgdorferi, a spirochete transmitted to humans by bites from I. scapularis (the blacklegged tick or deer tick) in Minnesota. In Minnesota, the same tick vector also transmits the agents of babesiosis, anaplasmosis, one form of human ehrlichiosis, and a strain of Powassan virus.
In 2014, 896 confirmed Lyme disease cases (16.5 cases per 100,000 population) were reported (Figure 1). In addition, 520 probable cases (physician-diagnosed cases that did not meet clinical evidence criteria for a confirmed case but that had laboratory evidence of infection) were reported. Despite some yearly fluctuations, the number of reported cases of Lyme disease has been increasing, as evidenced by the median number of cases from 2006 through 2014 (median, 1,065; range, 896 to 1,431) compared to the median from 1996 to 2005 (median, 464; range, 252 to 1,023).
Five hundred fifty-three (62%) confirmed cases in 2014 were male. The median age of cases was 39 years (range, <1 to 88 years). Physician-diagnosed erythema migrans (EM) was present in 582 (65%) cases. Three hundred fifty-one (39%) cases had one or more late manifestations of Lyme disease (including 267 with a history of objective joint swelling, 66 with cranial neuritis, including Bell’s Palsy, 4 with lymphocytic meningitis, 12 with acute onset of 2nd or 3rd degree atrioventricular conduction defects, and 4 with radiculoneuropathy) and confirmation by Western immunoblot (positive IgM ≤30 days post-onset or positive IgG). Of the 824 cases with known onset dates, onset of symptoms peaked from June through August, with 40% of EM cases experiencing symptom onset in July. This timing corresponds with peak activity of nymphal I. scapularis ticks in mid-May through mid-July. The majority of cases in 2014 either resided in or traveled to endemic counties in north-central, east-central, or southeast Minnesota, or Wisconsin.
- For up to date information see: Lyme disease
- Full issue>> Annual Summary of Communicable Diseases Reported to the Minnesota Department of Health, 2014