Lyme Disease
Annual Summary of Reportable Diseases

Lyme disease is caused by Borrelia burgdorferi, a spirochete transmitted to humans by bites from Ixodes scapularis, the blacklegged tick. Recently, a new species, B. mayonii, has also been identified as a cause of human disease, and 13 cases have been reported in Minnesota residents since 2013, two in 2022. Data for these cases is included in the summary data below. In Minnesota, the same tick vector also transmits the agents of babesiosis, anaplasmosis, one form of ehrlichiosis, and a strain of Powassan virus.

In 2022, a new national case definition for Lyme disease surveillance went into effect, and as a result, MDH changed its surveillance methods. As a high-incidence state for Lyme disease, Minnesota is no longer required to collect clinical information to classify each case and instead reports totals based on the number of people who have confirmatory lab testing. Because of this change, case numbers appear to have increased dramatically in 2022, but they are comparable to prior years. For a portion of Minnesota counties that are in emerging and low-incidence areas of the state, MDH continued to collect detailed data and will summarize that below. 

Under the new case definition, Minnesota identified 2,685 probable Lyme disease cases (46 cases per 100,000 population) based on confirmatory laboratory evidence. In addition, 24 suspect cases with only supportive laboratory results were also reported. The total number of laboratory reports for Lyme disease received in 2022 (3,148) was nearly identical to what was received in 2021 (3,128). The overall median age for all reports was 52 years old, which is comparable to past years. 

Of the 2,685 probable Lyme disease cases reported, 188 (7%) cases occurred in counties that are considered low incidence for Lyme and other tickborne diseases. Traditional case follow-up was performed for these cases and similar to the laboratory only data, the majority (56%) of cases were male. The median case age was 42 years (range, 2 to 96). Physician-diagnosed erythema migrans (EM) was present in 46 (24%) cases. Twenty-six (14%) cases had one or more late manifestations of Lyme disease, including 12 with a history of objective joint swelling, 10 with cranial neuritis including Bell’s Palsy, and three with acute onset of 2nd or 3rd degree atrioventricular conduction defects. Of the 150 (80%) cases with known onset dates, onset of symptoms peaked from May through September. This timing corresponds with the typical peaks in tick activity in the spring and early summer. Most cases either resided in or traveled to endemic counties in north-central, east-central, or southeast Minnesota, or Wisconsin.

• Find up to date information at: Lyme Disease (Borrelia burgdorferi)

Lyme disease is caused by Borrelia burgdorferi, a spirochete transmitted to humans by bites from Ixodes scapularis, the blacklegged tick. Recently, a new species, B. mayonii, has also been identified as a cause of human disease, and 11 cases have been reported in Minnesota residents since 2013, 1 in 2021. Data for these cases is included in the summary data below. In Minnesota, the same tick vector also transmits the agents of babesiosis, anaplasmosis, one form of ehrlichiosis, and a strain of Powassan virus. 

In 2021, 1,033 confirmed Lyme disease cases (18 cases per 100,000 population) were reported. In addition, 869 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. Overall, the number of reported cases of Lyme disease has been increasing for many years, despite yearly fluctuations. The median number of cases from 2010 through 2019 (median, 1,190; range, 896 to 1,431) was higher compared to the median from 2000 to 2009 (median, 915; range, 463 to 1,239) (Figure 1). Data for 2020 are not available due to surveillance changes made during the COVID-19 pandemic. 

Of the confirmed Lyme disease cases reported, 642 (62%) cases were male, and the median case age was 45 years (range, 2 to 94). Physician-diagnosed erythema migrans (EM) was present in 697 (67%) cases. Three hundred seventy-one (36%) cases had one or more late manifestations of Lyme disease, including 241 with a history of objective joint swelling, 108 with cranial neuritis including Bell’s Palsy, 6 with lymphocytic meningitis, 16 with acute onset of 2nd or 3rd degree atrioventricular conduction defects, and 1 with radiculoneuropathy, and confirmation by Western immunoblot (positive IgM ≤30 days post-onset or positive IgG). Of the 934 cases with known onset dates, onset of symptoms peaked from June through August, with 68% of EM cases experiencing symptom onset in June or July. This timing corresponds with peak activity of nymphal I. scapularis ticks in mid-May through mid-July. Most cases either resided in or traveled to endemic counties in north-central, east-central, or southeast Minnesota, or Wisconsin.

• Find up to date information at: Lyme Disease (Borrelia burgdorferi)

2020 data is not available.

• Find up to date information at:  Lyme Disease (Borrelia burgdorferi)

Lyme disease is caused by Borrelia burgdorferi, a spirochete transmitted to humans by bites from Ixodes scapularis, the blacklegged tick. Recently, a new species, B. mayonii, has also been identified as a cause of human disease, and 10 cases have been reported in Minnesota residents since 2013, 1 in 2019. In Minnesota, the same tick vector also transmits the agents of babesiosis, human anaplasmosis, one form of human ehrlichiosis, and a strain of Powassan virus.

In 2019, 915 confirmed Lyme disease cases (16 cases per 100,000 population) were reported. In addition, 612 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. Overall, the number of reported cases of Lyme disease has been increasing despite yearly fluctuations, as evidenced by the median number of cases from 2010 through 2018 (median, 1,203; range, 896 to 1,431) compared to the median from 2000 to 2009 (median, 915; range, 463 to 1,239) (Figure 1).

Of the confirmed Lyme disease cases reported, 551 (60%) cases were male, and the median case age was 48 years (range, 2 to 90). Physician-diagnosed erythema migrans (EM) was present in 650 (71%) cases. Three hundred fifteen (34%) cases had one or more late manifestations of Lyme disease (including 231 with a history of objective joint swelling, 69 with cranial neuritis including Bell’s Palsy, 4 with lymphocytic meningitis, 15 with acute onset of 2nd or 3rd degree atrioventricular conduction defects, and 7 with radiculoneuropathy) and confirmation by Western immunoblot (positive IgM ≤30 days post-onset or positive IgG). Of the 840 cases with known onset dates, onset of symptoms peaked from June through August, with 65% of EM cases experiencing symptom onset in June or July. This timing corresponds with peak activity of nymphal I. scapularis ticks in mid-May through mid-July. The majority of cases either resided in or traveled to endemic counties in north-central, east-central, or southeast Minnesota, or Wisconsin.

• Find up to date information at:  Lyme Disease (Borrelia burgdorferi)

Lyme disease is caused by Borrelia burgdorferi, a spirochete transmitted to humans by bites from Ixodes scapularis, the blacklegged tick. Recently, a new species, B. mayonii, has also been identified as a cause of human disease, and 9 cases have been reported in Minnesota residents since 2013, 1 in 2018. In Minnesota, the same tick vector also transmits the agents of babesiosis, human anaplasmosis, one form of human ehrlichiosis, and a strain of Powassan virus.

In 2018, 950 confirmed Lyme disease cases (17 cases per 100,000 population) were reported. In addition, 591 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 2009 through 2017 (median, 1,203; range, 896 to 1,431) compared to the median from 2000 to 2008 (median, 913; range, 463 to 1,239) (Figure 1).

Five hundred eighty-eight (62%) confirmed cases were male, and the median case age was 44 years (range, 1 to 91). Physician-diagnosed erythema migrans (EM) was present in 601 (63%) cases. Three hundred eighty-nine (41%) cases had one or more late manifestations of Lyme disease (including 282 with a history of objective joint swelling, 84 with cranial neuritis including Bell’s Palsy, 4 with lymphocytic meningitis, 20 with acute onset of 2nd or 3rd degree atrioventricular conduction defects, and 9 with radiculoneuropathy) and confirmation by Western immunoblot (positive IgM ≤30 days post-onset or positive IgG). Of the 876 cases with known onset dates, onset of symptoms peaked from June through August, with 69% of EM cases experiencing symptom onset in June or July. This timing corresponds with peak activity of nymphal I. scapularis ticks in mid- May through mid-July. The majority of cases 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 (Borrelia burgdorferi)

• Archive of Annual Summary of Communicable Diseases Reported to the Minnesota Department of Health
  Archive of past summaries (years prior to 2023 are available as PDFs).